Presentation : IMS – Tech Managers ConferenceAuthor : IMS StaffCreation date : 08 March...

Presentation : IMS – Tech Managers Conference Author : IMS Staff Creation date : 08 March 2012 Classification : D3 Conservation : Page : 1 04 - Power and Control Devices Author : IMS Stafff Creation date : 02 Nov 2012 Classification : D3

04 - Power and Control Devices


The intent of this presentation is to present enough information to provide the reader with a fundamental knowledge of electrical power and control devices used within Michelin and to

better understand basic system and equipment operations.


04 - Power and Control Devices

Module 1 – Relays and Contactors

Module 2 – Overload Relays

Module 3 – IEC and NEMA Components

Module 4 – Control Relay Applications

Module 5 – Timers and Contact Blocks

Module 6 – Solenoids

Module 7 – Troubleshooting Power and Control Devices


Module 1

Relays and Contactors

Module 1: Relays and Contactors


Theory of Operation


D am per

C ase

S had ingR ing

M agneticC ircu it C o il

R eturnS pring

C ontactsM ovingS upport


Theory of Operation

Purpose

Both relays and contactors provide a means of automatic operation of a machine from a remote location.

A contactor belongs to both the control circuit and the power circuit. The contactor coil and auxiliary contacts such as those required to seal-in or provide electrical interlock are found in the control circuit. The remaining main contacts are used to switch loads in the power circuit.

A relay is always used in the control circuit. It is used to remember machine events such as the momentary closure of a limit switch contact. It is also used to overcome contact constraints, such as, incorrect type or not enough normally open or normally closed contacts available on a particular device.



Theory of Operation

Operation and Construction

Case or Housing

Contains all the parts and provides the insulation

necessary to isolate individual contacts.

Contacts

Main contacts, usually three and each of them having

Fixed contact

Movable contact

Sometimes an arc blow-out device

Auxiliary contacts, usually on the device or added

and having Fixed contact; Movable contact

Different types: Normally open contact; Normally closed contact

Note: Auxiliary contacts should open and close at the same time as the main contacts and can be used to control various other circuits.


D am per

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S had ingR ing


R eturnS pring



Theory of Operation

Return Spring

This spring insures that the moveable core rapidly moves

away for the stationary core when the coil is de-energized.

This rapid opening insures that the contacts, both main

and auxiliary open as quickly as possible.

Electromagnet

The main feature of a contactor that distinguishes it from

a manual starter is the use of an electromagnet.

The electromagnet is ultimately responsible for

switching the state of the contacts. The electromagnet

consists of the following:


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S had ingR ing


R eturnS pring



Theory of Operation

Coil

The coil produces magnetic flux as the result of current

flow. The impedance of the coil limits the current in

an AC circuit. The coil's impedance is mainly inductive

reactance since the coil usually has a very low internal

resistance.

Note: Only the DC resistance of the coil limits

the current in a DC circuit.

Stationary Core

The stationary core concentrates magnetic flux. In doing

so, this core's surface, which mates with the moveable

core, is polarized and attracts the moveable core.

This core is constructed of laminated steel to reduce Eddy currents.


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Theory of Operation

Movable Core

The moveable core also concentrates magnetic flux.

The moveable core concentrates magnetic flux radiating

from the mating surfaces of the stationary core. As a

result, the mating surfaces of the moveable core are

attracted to the stationary core resulting in the movement

of the moveable core against the stationary core. The

moveable core is attached through a plastic or insulated

assembly to the contacts.

As the moveable core is pulled against the stationary core,

the contacts change state. Since the moveable core is

made to move, it is often referred to as the armature.

This core is also constructed of laminated steel to reduce Eddy currents.


D am per

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S had ingR ing


R eturnS pring



Theory of Operation

There are two inherent problems when an AC voltage is applied to a relay or contactor coil.

The change in magnetic flux with respect to time induces a voltage in the core resulting in undesirable induced currents called eddy currents.

The core is constructed of laminated steel to reduce these eddy currents. Laminations serve to increase the electrical resistance of the core. If the resistance of the core is doubled, the current is halved. Then from Watt's Law, we see that a reduction in current results in a significant reduction in power since P = I2R. Eddy currents are undesirable because they result in power dissipated by the core in the form of heat.


Small Eddy CurrentsLarge Eddy Currents


Theory of Operation

The magnetic flux produced by the coil also goes to zero twice per cycle due to the alternations of the sine wave. Since there is no magnetic attraction, the two cores try to pull apart during these two instants in time. Since this pulling apart would cause the relay or contactor to chatter, something must retain the magnetic attraction during these times. Shading rings are embedded in the surface of the stationary core. These rings retain magnetic flux as the coil current passes through zero. The amount of magnetic flux produced by the coil is proportional to the current through the coil. As coil current passes through zero, it is making its greatest change with respect to time. Since the flux and current are in phase, flux is also making its greatest change with respect to time. This rapid change in flux causes an induced voltage and thus current to flow in the shading ring. As the result of current flow in the shading ring, a small magnetic field is created. The strength of this magnetic field is sufficient to retain the attraction of the two cores during the instant the main magnetic field passes through zero.


0 0

900

1800

2700

3600

Shading Ring Flux

Coil Current+

-

Main Flux


Theory of Operation

The contactor and relay functions mechanically exactly the same.

The cross-section drawing below shows how the moveable contacts are mechanically connected to the moveable part of the magnetic circuit. When the moveable part of the magnetic circuit is pulled against the return spring, the moveable part of the contacts either closes or opens relative to the stationary set of corresponding contacts.

The illustration shown is a mechanical representation of

the contactor. The moveable and stationary contacts

must be electrically insulated and isolated from each other,

the magnetic circuit and the coil.

There are many different variations of contact

configurations.


M echanica l D raw ing C ross-Section

C oil

R eturnSpring

C ase

M oveableC ontacts

M ovingSupport

M agneticC ircu it

S ta tionaryC ontacts


Theory of Operation

There are more than one symbols for a contactor or a relay. These devices are a combination of many symbols, such as contacts and coils. Below is an electrical representation for a contactor and a relay. Both contain a coil that has terminal numbers A1 and A2. The contactor has three main contacts numbered L1 –T1, L2 – T2, L3 – T3, which are designed to carry heavy loads to motors, heaters, etc. The darker lines show these main contacts. The contactors auxiliary contacts are shown with smaller lines and numbered 13 – 14. The relay has all smaller auxiliary type contacts with different numbers. The numbers will be different for different configurations of contacts. The one shown is two normally open and two normally closed.


E lectrica l R epresenta tion for a C ontactor

L113

14

L3L2

T 1 T 3T 2A 2

A 1

E lec trica l R ep resen ta tion fo r a R e lay

A 2

A 143

44

31

32

21

22

13

14


Theory of Operation

Coil Specifications and Definitions

Pick-up voltage - The minimum voltage that causes the armature to move

Seal-in voltage - The minimum voltage that will keep the armature against the stationary core.

Drop-out voltage - The voltage at which the armature starts to move away from the stationary core.

Nominal coil voltage - The ideal voltage for which the coil is designed. A relay or contactor will typically operate properly when the actual voltage applied is 85 to 110% of the nominal voltage. Example: If the nominal voltage is 120v, then the typical operating range is 102-132 volts.



Theory of Operation

Coil VA rating

The apparent power rating of the coil depends upon armature position and is specified as inrush and sealed. Inrush condition occurs when the voltage is applied to the coil but the armature has not moved completely against the stationary core.

The sealed condition occurs when the armature is completely seated against the stationary core. Typical VA ratings for a standard relay or contactor coil could be 80VA inrush and 7VA sealed. For a coil with a nominal voltage of 120 volts, this translates to 667 mA inrush current and 58.333 mA seal-in current.

This difference in current from inrush to seal-in is approximately 10-12 times greater .

This large difference in current can be directly related to coil failure. This is due to excessive current in the coil if the armature does not become sealed properly or in a reasonable amount of time.



Theory of Operation

As the term inrush implies, there is an inrush of current when the coil is initially energized. This inrush of current is the result of the armature position (unseated). When the armature is not seated, the impedance of the coil is low resulting in an excessive amount of current (inrush). Since the internal resistance of the coil is very low, the inductance of the coil is the main determining factor for the impedance.

The inductance of the coil is directly proportional to the coil core’s permeability. On the next pages we will discuss how permeability of the core affects the current in the coil.

Permeability is a measure of a material’s ability to concentrate magnetic flux .

Relative Permeability is a measure of a material’s ability to concentrate magnetic flux as compared to air (air being equal to 1)



Theory of Operation

When the armature is not seated, the relative permeability of the coil's air core is very low (approximately equal to unity or 1). This results in low inductance, low inductive reactance, and thus low impedance. The following equation gives the relationship between inductance (L), relative permeability (r) and the coil size.

A coil's inductance depends on how it is wound, the core material on which it is wound, and the number of turns of wire with which it is wound.

1. Inductance increases greatly as the number of turns of wire around the core increases since it is squared.

2. Inductance increases as the relative permeability of the core material increases. The relative permeability of air is approximately 1 and the relative permeability of an iron core is approximately 400-500 times greater than that of air.

3. Inductance increases as the area enclosed by each turn increases. Since the area is a function of the square of the diameter of the coil, inductance increases as the square of the diameter.

4. Inductance decreases as the length of the coil increases (assuming the number of turns remains the constant).


L = N A

lr

2


Theory of Operation

For the relationship below, if the number of turns, area of the core, and the length of the core all remain constant for a given coil; then the permeability of the coil's core is the determining factor for the inductance of that coil. For an air core (r = 1), the inductance is very low. For an iron core (r = 500), the inductance is very high.

In this relationship, if the inductance increases, then the inductive reactance increases. If the inductance decreases, then the inductive reactance decreases. Inductive reactance is the opposition to AC current due to the inductance in the circuit.

In the case of an air core, XL is very low, and the current in the coil is high. In the case of an iron core, XL is very high, and the current in the coil is low.


in measured reactance, inductive = X

Hz in measured frequency, = f

h in measured ,inductance = L where

f2X = L

L

L

I = V

X L


Contactor Applications

Direct-On-Line Starting of an AC Motor

This is the simplest method of starting AC motors. The expression "direct-on-line starting" means that the full electrical supply voltage is connected directly to the motor terminals, usually by means of a "contactor".

Seal-in Circuit

In order to comply with the requirements of the relevant regulations, a D-O-L starter comprises:

1. Efficient means for starting and stopping the motor.

2. Means to prevent automatic restarting (known as under-voltage protection or “seal-in circuit”) after a stoppage due to a drop in voltage or complete failure of supply, where unexpected restarting of the motor might cause injury to an operator.

3. A suitable device providing means of protection against excess current in the motor or in the cables between the device and the motor. This is known as "over-current protection".





DISC

L1

L2

L3

1L1

1L2

1L3

M OL

460 V60 Hz

T1

T2

T3

MTR

1FU

2FU

3FU

2L2

2L1

2L3

1 23 4 5

OL 1PB 2PB

M

STOP START

M

6FU NL

4FU 5FU

H1 H3 H4H2

3L2 3L3

X1 X224 V

T



Direct-On-Line Reversing

Motor starters are used when it is desired to reverse the direction of rotation of a three-phase squirrel-cage motor. The standard arrangement consists of a set of two, three pole; contactors operated electro-magnetically and mechanically linked together. They are usually controlled by three push buttons: Forward, Reverse, and Emergency Stop. The connections of one contactor reverse the supply voltage to two of the three motor terminals.


1M F

1M R

1L1

1L2

1L3

1F U

2F U

3F U

1O LT1

T2

T3M T R

2L2

2L1

2L3

1

TO NEXT PAG E

1D IS C

L1

L2

L3

480 V

60 H z



Electrical and Mechanical Interlocking

Opposing motions shall be electrically interlocked, as well as, mechanically interlocked. The mechanical interlock will not allow both forward and reverse contactors to be energized at the same time. If this could happen, 2L1 and 2L3 would be tied to T1 and T3 at the same time causing a short circuit.

The electrical interlock (N.C. 1MF and 1MR) protects the coils for 1MF and 1MR.

Example: If 3PB were pressed while the

machine is running forward, inrush current

would flow through 1MR coil. Since the

mechanical interlock is stopping the contactor

from closing, the moveable core stays open

which would cause the coil to overheat and

destroy itself.


1 3

1OL 1PB

STOP

24 5

2PB

1MF

FORWARD

1MF

7

3PB

1MR

REVERSE

1MR

1MR

1MF

6

8



Design Techniques for Limit Switches

There are many different techniques for limit switches when applied to a control circuit. The techniques and physical locations of the limit switches illustrated below are examples of recommendations and not requirements.

1. One technique is a limit switch used as a control stop device to prevent moving parts of machines from over-running the normal mechanical limits of the machine. Notice the location of 1LS in the circuit below. It is located in the right side of the schematic as a control stop device. The machine will stop when 1LS is actuated and is limited to that amount of travel only. This ensures that moving parts are brought to rest at the correct position. 1LS is using a normally closed (N.C.) contact for this operation. Control stop devices stop machines for normal operations.


1 3 4 5

1M

6 2

1OL 1PB2PB

1LS

1M




2. The configuration below is an example of the same circuit above except the limit switch is shown in the held position to represent the home position for the machine. 1LS is using a normally closed contact but it is held open (N.C.H.O.) to designate the home position.


1 3 4 5

1M

6 2

1OL 1PB2PB

1LS

1M




3. Another technique is a limit switch used as

a control start device. To reverse the motion

of the machine at the end of a stroke, 2LS is

used as a control start device and is located

in the middle of the schematic. Notice that 3PB is also a control start device for the reverse motion and 2PB is for the forward motion. Notice that 1LS

and 2LS are used as control stop devices.

When the forward motion moves the machine

from the 1LS position to the 2LS position, the

motor forward contactor will de-energize by 2LS (N.C.) and the forward motion will stop. Now 2LS (N.O.) also closes and will reverse the motion of the

machine back to the home position (1LS).


3

1OL

ESTOP

4 5

2PB

1MF

FORWARD

1MF

8

3PB

REVERSE

1MR

1MR

1MF

6

10

7

9

1LS

1PB

1 2

2LS

1MR

2LS




4. Another technique is a limit switch used as a safety stop device for safety conditions to be met before the machine can be started.

Example: Limit switches on lift gates or guards protecting operators from moving parts of machinery. Notice the location of 1LS in this circuit. It is located in the left portion of the schematic as a safety stop device. Opening the gate or guard will stop the machine. 1LS is using a normally closed (N.O.H.C.) contact for this operation. 1 LS and 1PB are personnel safety stop devices. 1OL is an equipment safety stop device.


1 3 4 5 6 2

1OL 1PB

1M

1M

2PB1LS


Forward-Reverse Contactor with Limit Switches to Control Stopping of the Opposing Motions


1T

H1 H3 H2 H4

X1 X2

1 3

1OL 1PB

STOP

6FU 1NL

24 V

24 5

2PB

1MF

FORWARD

1MF

8

3PB

1MR

REVERSE

1MR

1MR

1MF

7

10

4FU

3L1

1L1

FROM LAST PAGE

5FU

3L2

1L2

6

1LS

2LS

9


Automatic Forward-Reverse Contactor with a Limit Switch to Start the Opposing Motion


1T

H1 H3 H2 H4

X1 X2

1 3

1OL 1PB

STOP

6FU 1NL

24 V

24 5

2PB

1MF

FORWARD

1MF

8

3PB

1MR

REVERSE

1MR

1MR

1MF

7

10

4FU

3L1

1L1

FROM LAST PAGE

5FU

3L2

1L2

6

1LS

2LS

9

1LS

UP

DOWN


Simple Contactor with 2 Start Pushbuttons


DISC

L1

L2

L3

M OL

460 V60 Hz

T1

T2

MTRT3

2L2

2L1

2L3

1FU

2FU

3FU

1 26

OL 3PB

M

M

6FU NL

4FU 5FU

H1 H3 H4H2

3L2

3L3

X1 X224 V

T

4PB

2PB1PB

4 53

1L1

1L2

1L3


This Concludes

Module 1

Relays and Contactors



Module 2

Overload Relays

Module 2: Overload Relays


Construction


C O VE R

B I-M E T AL

C AS E

C O N T AC T S

R E T U R N S P R IN G

R E S E T B U T T O N

T R IP P IN G S L ID E

AD JU S T IN G L E VE R

C AM

U P P E R D IF F E R E N T IAL O P E R AT O R

L O W E R D IF F E R E N T IAL O P E R AT O R

D IF F E R E N T IAL L E VE R

T E L E M E C A N IQ U EL R 1 -D

M O VIN G C O N T AC T

S U P P O R T

B I-M E T AL

T H E R M AL C O M P E N S AT IO N


O/L Specifications

Operating Ranges

Maximum Voltage: 600V AC or DC

Frequency Range: up to 400 Hz

Contacts: 1 Normally Open and 1 Normally Closed

Ambient Temperature Compensation

From - 4 to 140 °F

-20 to 60 °C

Differential: Phase loss and phase unbalance detection


LR1-DO9 LR1-D12 LR1-D16 LR1-D25 LR1-D40 LR1-D630.1-0.16A0.16-0.25A0.25-0.4A 0.4-0.63A0.63-1.0A

1-1.6A1.6-2.5A2.5-4A4-6A5.5-8A7-10A

10-13A 13-18A 18-25A 23-32A30-40A

38-50A48-57A57-66A


Adjustment and ResettingFunction

Adjustment - Adjusting dial must be set to read the full load current of the motor (FLC).

Resetting - Resetting is done by pressing the blue reset button after the bi-metal elements have been allowed to cool down.



Mechanical Operation.


Therm a l C om pensa tion B i-M eta lT ripp ing

S lide

R ese t B u tton

C ase

B i-M e ta ls

D if fe ren tia l O pera to rC am M ov ing C on tac t S upport

C on tac ts

R e tu rnS pring


Differential Operation

Cold Position - The differential operators are hard over to

the right

Warm Position - NORMAL BALANCED CURRENT - The 3

bi-metals and the operators move to theleft the same distance d

Warm Position - BALANCED OVER CURRENT - The 3

bi-metals and the operators move over to the left the same

distance which trips the overload relay. Tripping current is 125%

of the actual adjusting dial value

Warm Position - UNBALANCED CURRENT - The unbalanced current

causes unequal deflection of the 3 bi-metal strips. The differential lever

amplifies this unequal deflection. The distance d is also amplified and

causes the mechanism to trip. The tripping current for an unbalanced

current is equal to 80% of the current for 3 balanced phases


d

d

d


Features


LR2D Bimetallic Overload Relays* Class 10 Protection - 0.10 to 140 Amps* Class 20 Protection - 2.5 to 80 Amps* With or Without Phase Loss and Phase

Unbalance Protection* Ambient Temperature Compensated* High Resistance to Shock and Vibration* Proven Reliable Protection * Withstand in Excess of 17X Thermal Rating* Precise Settings by Graduated Dial* Separate Stop and Reset Functions* Manual/Auto Reset Selector* Setting Dial Cover can be Sealed* Trip Indication/Test Button on Front* Lockable Cover* Remote Reset - Remote Test* Direct Mounting to D-Line Contactors or Panel

Mounting with Optional Bracket


Features


BenefitsB1-Stop function for

instantaneous circuit isolation

B2-Manual position for local or automatic position for

B3-Provides visual indication of trip status

B4-Easily adjustable trip rangeB5-Provides visual indication

and protection against unwanted tampering of reset and trip settings

B6-Provides flexibility in installations in control panels

B7-Overload not affected by temperature

FeaturesF1-Separate Stop and Reset

FunctionF2-Reset Button can be

Switched from Manual to Automatic Position

F3-Trip Test Button with Indicator

F4-Full Load Current Trip Setting with Graduated Dial

F5-Clear Cover for Manual/Auto Reset Selector and Trip Range Dial can be Sealed

F6-Mounts directly to contactor or to bracket for panel mounting

F7-Ambient compensated


This Concludes

Module 2

Overload Relays



Module 3

IEC and NEMA Components

Module 3: IEC and NEMA Components



The Organizations and Goals

IEC - The IEC (International Electro-technical Commission) was conceived as an idea in 1904 during a meeting of the International Electrical Congress in St. Louis, Missouri. The first meeting of the IEC was held in London, England, in 1906. Its voting body consists of 42 member nations, each having one vote on the Commission. The United States is one of the voting members. Presently, the IEC is headquartered in Geneva, Switzerland. The IEC is international and its activities have traditionally been associated with equipment used in European common market countries.

The IEC has developed recommendations to which manufacturers may test and publish technical information that provides potential customers with a basis for product comparison.

"IEC Type" starters, contactors or overload relays refer to devices manufactured and tested per IEC recommendations.




NEMA - NEMA (National Electrical Manufacturers' Association) was formed in 1926 and is headquartered in Washington, D.C. NEMA presently has 550 members, most of who are North American manufacturers of electrical and electronic products. The activities of NEMA have predominantly been associated with equipment used in North America.

The primary goal of NEMA is to establish standardization within North American electrical industry. NEMA has developed product design standards and test specifications for device qualifications, many of which have been adopted by UL (Underwriters Laboratories). NEMA specifies the ratings a device must carry in order to be labeled with a NEMA designation. For example, a contactor must show motor ratings of 10 HP @ 460 volts and 7.5 HP @ 230 volts on its nameplate to be designated "NEMA Size 1."

IEC and NEMA do not perform device testing. The manufacturers of the equipment do testing. IEC does publish parameters for life testing of contactors -- NEMA does not. The IEC life test does not state what the overall test results should be. However, they do recommend that the minimum electrical life of a contactor should be at least 1/20 of its mechanical life.

"NEMA Type" devices refer to those traditionally supplied by the major U.S. manufacturers of motor controls.




UL - Underwriters Laboratories was founded in 1896 as a private laboratory. Initially, its work involved testing equipment for insurance companies. UL directs its attention to verifying that an electrical product will not cause fire or shock when properly installed. The UL listing mark is significant to market acceptance of products in the United States.

NEMA, UL or IEC does not dictate levels of electrical or mechanical life. In Europe and North America, the market dictates the level of device performance.

Confusion can result when two devices showing the same horsepower rating are significantly different in size. The traditional NEMA type contactor, designed to provide a very high level of performance, is larger than the equivalently rated IEC type device. Size difference is more evident among contactors below 50 horsepower (at 460 volts). At 50 horsepower and above, the size difference is less evident because of the larger arc to be extinguished when the contacts are opened. Emphasis is placed on the small frame devices because 80% of the contactors and starters used in the world are less than 50 HP. These devices did not evolve differently because of IEC and NEMA. Market requirements influenced manufacturer design.

To some degree differing economic conditions in the two parts of the world led to different market requirements and, as a result, different approaches toward the manufacture of electrical contactors.



IEC and NEMA Contactors

IEC Type - In Europe there has historically been relatively short supply and high cost of raw material. In the interest of conserving materials, designers considered the average application and used no more material than was required. This resulted in smaller size devices per horsepower rating, and therefore devices that are more application sensitive. Greater knowledge and care are necessary for proper application.

NEMA Type - In North America, materials were plentiful and relatively inexpensive. The market demanded a very high level of performance throughout a wide range of motor applications. As a result, this eliminated much of the possibility of human error in application because it became extremely simple to select the appropriate device for a given application. Very rarely did the designer have to know any more than the horsepower and voltage of the motor to select the proper size device.

Both types of contactors provide advantages. The designer makes the choice based on usage considerations.




Application

IEC type and NEMA type contactor application information and philosophy differ significantly. IEC type application information must be understood in order to achieve the desired level of device performance.

IEC Type Contactors

The primary function of the IEC is to recommend contactor test criteria and procedures which manufacturers may use to test and publish results. Published IEC type technical information is a statement of IEC recommended test results. A judgement must be made regarding how the laboratory test results actually relate to specific applications.

One million electrical operations and a mechanical life of 10 million operations are generally accepted expectations for IEC contactors below 50 horsepower (These expectations are based on a standard squirrel-cage motor operating under normal conditions). Life expectations are less for contactors 50 horsepower and above. These levels of performance originated as a European market requirement for contactors.




NEMA Type Contactors

At the smaller horsepower ratings, electrical life expectations for traditional NEMA type contactors on tests per the IEC recommendations would be between 2.5 and 4 times greater than equivalently rated IEC type devices. Expectations vary based on manufacturer. In the middle sizes, the differences in expectations decrease. In the very large sizes, electrical life expectations of NEMA type and IEC type devices are about the same.

NEMA type contactors provide a high level of performance for a wide range of applications, including some jogging duty. Some refer to that as extra or reserve capacity.

Short Circuit With-Stand-Ability

NEMA type contactors and overload relays are designed to withstand the let-through energy of a short circuit protective device available in the U.S. IEC devices were designed for coordination with fast acting European style fuses. Care must be taken in their application with slower acting U.S. fuses to avoid severe damage to circuit components



IEC and NEMA Overload Relays

NEMA Type Overload Relay

The most common NEMA type overload relay is a stored energy, eutectic-alloy device (also called solder pot or melting alloy overload relays) that utilizes a special alloy that melts when damaging overload currents are present. This allows a ratchet wheel to spin free and release spring-loaded electrical contacts to de-energize the contactor and disconnect the motor from the line.

The current in each phase of the motor is passed through a separate heater coil to heat an individual thermal unit containing the eutectic alloy. Because this type of overload relay senses current in each line independently, it will protect a motor from overload conditions as a result of single phasing or unbalanced currents. When the current in any one line exceeds the safe operating current for the motor, beyond the specified time limits, the overload relay will trip.

The typical NEMA type overload relay utilizes interchangeable heater coils. This not only allows the device to easily and inexpensively be adjusted to protect motors of varying full load current at the same horsepower rating, but allows the same overload relay to be used with motors of a different horsepower rating, for different system voltages.




IEC Type Overload Relay

IEC type overload relays are bimetallic devices. A bimetal is made up of two strips or more of metal having different coefficients of expansion, attached together such that when heated, the metals expand at a different rate and cause the bimetal to bend. Motor current is utilized within the overload relay to heat three separate bi-metals, one per phase. An overload causes the bi-metals to operate a set of contacts, de-energizing the contactor and disconnecting the motor from the power lines.

The IEC type overload relay is designed to provide single phase sensitivity. This sensitivity results in overload protection under single phase conditions. If one of the phases should be lost, one of the bimetal elements is not heated. The force it contributes toward operating the overload relay is also lost. The IEC type overload relay includes a mechanical means to compensate for this loss. As two bi-metals push forward, being heated by current, the differential operators sense this phase loss and cause the relay to trip.

The IEC type overload relay is also designed to provide ambient temperature compensation. The overload relay is normally located in a different environment than the motor. Because of this, a fourth bi-metal strip is located in the overload relay to provide for ambient compensation for the temperature of its environment. A properly designed ambient compensating element reduces the effect on the overload relay caused by ambient change. This allows an overload relay of this configuration in a varying ambient temperature to properly protect the motor.




IEC Type Overload Relay

The IEC type overload relay is also designed to provide mechanical trip adjustment. This adjustment allows a particular overload relay to be used for a different range of motors. Most new type IEC overload relays are designed to be adjusted in the field for either manual or automatic reset operation.



This Concludes

Module 3




Module 4

Control Relay Applications

Module 4: Control Relay Applications


Control Circuit Grounding Systems

Control Voltages

24 Volt Control Circuit - This voltage is considered as a safe voltage and must be obtained by using an isolated type transformer (auto transformers are not allowed). It guarantees adequate protection for personnel and must be used in damp areas.

120 Volt Control Circuit - This voltage is not to be considered as a safe voltage and must be obtained by using an isolated type transformer (auto transformers are not allowed).

Control System Examples

1. An ungrounded control circuit used with either a 24V or 120V control transformer.- The secondary side of the transformer is

not grounded- The control circuit must be protected by

two fuses


H1 H3 H4H2

T

6 Fu

1

7Fu

X1 X2

23 4 5 6

1OL 1PB

2PB

1LS

1M

1M

B CA



Control Voltages

- A ground fault at A, nothing happens.

- A ground fault at A and B, the control devices between wire #1 and 6 are shorted out due to a current path around them. Therefore, the machine goes out of control. Contactor 1M is energized and neither the overcurrent relay nor the stop button can de-energize it.

- A ground fault at A - and C, 6 Fu or 7 Fu, - and possibly both, - will open.

This type circuit is not acceptable due to safety hazards.


H1 H3 H4H2

T

6 Fu

1

7Fu

X1 X2

23 4 5 6

1OL 1PB

2PB

1LS

1M

1M

B CA



2. A grounded control circuit used with a 120V center tap control transformer.

- The center tap of the transformer is grounded.

- The control circuit must be protected by two fuses.

A ground fault at A, 6 Fu opens because there is a short circuit across the left side of the transformer. Contactor 1M remains energized if it was energized before the ground fault occurred, since 60 volts is enough to hold it in.


H1 H3 H4H2

T

6 Fu

1

7Fu

X1 X2

23 4 5 6

1O L 1PB

2PB

1LS

1M

1M

A

B



- A ground fault at B, 7 Fu opens because there is a short circuit across the right side of the transformer. Contactor 1M remains energized if it was energized before the ground fault occurred, since 60 volts is enough to hold it in. In both cases the ground fault will not be noticed until the machine is stopped and an attempt to be started again.



H1 H3 H4H2

T

6 Fu

1

7Fu

X1 X2

23 4 5 6

1O L 1PB

2PB

1LS

1M

1M

A

B



3. A grounded control circuit used with a 120V center tap control transformer and a ground fault relay (GFR).

- The center tap is grounded through a 60 volt ground fault relay.

- The control circuit must be protected by two fuses.


7 Fu

1

8Fu

23 4 5 6

1OL 1PB

2PB

1LS

1M

7

8

6 Fu

GFR

H1 H3 H4H2

T

X1 X2

1M

GFR

1LT

CBA



A ground fault at A or B or C, the relay GFR gets energized and indicates the fault (1LT is on). The machine continues to function. This circuit is to be only used whenever the interruption of the machine causes product damage. An example would be a production area where the product would be damaged beyond repair if the cycle was interrupted and the cost would be very large.


7 Fu

1

8Fu

23 4 5 6

1OL 1PB

2PB

1LS

1M

7

8

6 Fu

GFR

H1 H3 H4H2

T

X1 X2

1M

GFR

1LT

CBA



Note: A ground fault at A or B has to be repaired as soon as possible. If a second ground fault occurs on the left side of the coil (A or B whichever was first) the machine goes out of control. A ground fault at C also needs to be repaired as soon as possible because if a second ground fault occurs on the left side of the coil (A or B) 7 Fu and/or 8 Fu opens, which opens the circuit and interrupts the machine's operation.

This grounded control circuit is considered to be safe as far as keeping good control of the machine's operation. But don't overlook that all metallic parts have to be grounded properly in order to protect personnel against electrical shocks.


7 Fu

1

8Fu

23 4 5 6

1OL 1PB

2PB

1LS

1M

7

8

6 Fu

GFR

H1 H3 H4H2

T

X1 X2

1M

GFR

1LT

CBA



4. Grounded control circuit used with a 24 volt or 120 volt control transformer.

- X2 terminal of the secondary must be grounded.

- One side of the coil must be connected to this terminal through a neutral link (1NL).


H1 H3 H4H2

T

6 Fu

1

1 NL

X1 X2

23 4 5 6

1O L 1PB

2PB

1LS

1M

1M

A

B



- A ground fault at A, 6 Fu opens. No more voltage is applied to the control circuit.

- A ground fault at B, nothing happens. The first ground fault occurring at the left side of the coil 1M

will open the fuse 6 Fu and de-energize the circuit.

General Conclusion

The control system #3 is

adopted for special applications

only. The control system #4 is

the one adopted by most

manufacturers to control

machinery. It has proven to be

the safest for both personnel

and equipment.


H1 H3 H4H2

T

6 Fu

1

1 NL

X1 X2

23 4 5 6

1O L 1PB

2PB

1LS

1M

1M

A

B



Control Relay Master Circuit

This circuit is designed to protect the system if any of the safeties in the circuit are activated. When the safeties are activated the CRM coil is de-energized which disables the rest of the circuit.

The system would then have to be rearmed to

allow the circuit to be restarted.


H1 H3 H2 H4

X1 X2

4FU 5FU

1T

L1 L2 L31DISC

1L1

1L2

1L3

MTR

1M1FU

3FU

2FU

2L1

2L2

2L3

1T1

1T2

1T3

1OL

3L1 3L2

7FU

3

6FU

CRM

1NL

1OL 1PB

1

CRM

1LT

G

1PS 1LS 2LS 2PB

CRM

CRM

M3PB

M

4 2

5 6 7 8 9 10

11 12



Jog Circuits

Using only pushbuttons to create a jog circuit will only work if the contacts change states a certain way. When the JOG button is pressed, the normally closed contacts have to break before the normally open ones close. When the JOG button is released the normally open contacts have to break before the normally closed ones close again. With most pushbuttons this causes a race problem with the contacts and sometimes the contactor will seal in even when jogging. The only way to insure that the contacts won’t have a race condition is to use a separate control relay.


H1 H3 H2 H4

X1 X2

4FU 5FU

1T

6FU

1OL 1PB

1 3

1NL

1M

1M

RUN

JOG



Jog Circuits

Using a control relay as below insures that the race condition is eliminated.


H1 H3 H2 H4

X1 X2

4FU 5FU

1T

6FU

1OL 1PB

1 3

1NL

1CR

1M

1CR

1CR

RUN

JOG


This Concludes

Module 4

Control Relay Applications



Module 5

Timers and Contact Blocks

Module 5: Timers and Contact Blocks


Timer Types

The concept of using timers in electrical circuits is a very common practice. There are many ways to utilize timing functions and there are many types of timers. In this section the pneumatic type will be discussed and illustrated. Below are the two types which are used in common wiring practices. There is an ON delay type and an OFF delay type. Notice that there are two sets of contacts on each timer. One set is normally open and the other is normally closed. Above the contacts are shown with dotted lines between the normally open and normally closed set.

This shows a mechanical connection between each set of

contacts. This dotted line is not indicated on the schematic.

There is a different method of showing that the contacts belong t

o the same device. Once the timer is clipped onto the control relay,

it becomes a timing relay. The designation for that is TR. If it is

the first timer in the circuit, it becomes 1TR. Any contacts used

from this timing relay will be called 1TR. There will be auxiliary

contacts available to be used from this relay part of this timing

relay. These contacts will not have any timing function.

Module 5: Timers


Timer Types

For an example, if we use a relay that has 2 standard normally open contacts and 2 standard normally closed contacts as our timing relay, then those contacts will operate just as a control relay. We clip an ON delay timer on this relay. We have available to use 2 timed contacts, 1 normally open and 1 normally closed.

A timer block can not function without a control relay.

Module 5: Timers


Pneumatic Timer Operation (Off Delay Type)

Timer Initiation: When the coil is energized, the plunger will be pulled to the left by the movable magnetic circuit. The movable contact blade will then move from its rest position to the actuated position. Since the plunger is mechanically linked to the diaphragm, it will move left and compress spring A. The air contained in Chamber B is transferred into Chamber C through the opening D. This takes only a short period of time. The contacts change states almost instantaneously from their original positions. The N.O. contacts will close and the N.C. contacts will open.

Timing Period: When the coil is de-energized, Spring A will push back the diaphragm thus creating a vacuum in Chamber B. Then the air contained in Chamber C will be forced through a metal filter. The airflow speed is regulated by a variable length groove fitted between two discs. This timing effect is obtained by varying the relative position of these two discs. The variation of the discs is made possible by a setting knob.

Module 5: Timers

A djustab le D isk C hanne l

F ixed D isk C hanne l

C ham ber B

S pring A

P lunger A ctuated by theC ontro l R e lay

O pening D

D aphragm

C ham ber CF ilte r


Pneumatic Timer Operation (Off Delay Type)

End of Timing Period: When the diaphragm returns to its original position, the contact blade snaps to the off position (rest). The N.C. contacts will close back to the original position and the N.O. contacts open to the original position.

Module 5: Timers

A djustab le D isk C hanne l

F ixed D isk C hanne l

C ham ber B

S pring A

P lunger A ctuated by theC ontro l R e lay

O pening D

D aphragm

C ham ber CF ilte r


Pneumatic Timer Operation (On Delay Type)

Timer Initiation: This happens when the coil is energized and not de-energized as in the illustration before. The N.O. contacts remain open and the N.C. contacts remain closed.

Timing Period: When the coil is energized, the timing period begins. During the timing period the contacts remain in their normal positions.

End of Timing Period: At the end of the timing period the N.O. contacts close and the N.C. contacts open.

Module 5: Timers


Pneumatic Timer Symbols and States

Module 5: Timers

Timers

Contact ConfigurationOn Delay

At Rest Power On Power On + Time Power Off Power Off + Time

CoilVoltage

On

Off

Contact ConfigurationOff Delay

At Rest Power On Power On + Time Power Off

CoilVoltage

On

Off

Power Off + Time


Auxiliary Contact Blocks

Auxiliary blocks are necessary when the control relay or contactor do not have the exact amount of contacts to do the job. Auxiliary contact blocks can also come in various types and configurations. Illustrated below is an auxiliary contact block with four sets of contacts and one with two sets of contacts. The four contact type could be 2 N.O.-2 N.C., or 4 N.O., or 4 N.C. and other variations. The two contact type could be 1 N.O.-1 N.C. or 2 N.O. or 2 N.C.

As with the timer block, the auxiliary blocks can not function without a control relay or contactor .

Module 5: Timers

LA1 DN 22

TelemechaniqueET

53 NO 61 NC 71 NC 83 NO

54 NO 62 NC 72 NC 84 NO

TelemechaniqueET

LA1 DN 11

53 NO 61 NC

54 NO 62 NC


This Concludes

Module 5

Timers

Module 5: Timers


Module 6

Solenoids

Module 6: Solenoids


Understanding Solenoids

Description:

A solenoid is basically just an electrically-controlled valve that uses solenoid action to operate a mechanical valve. The voltage is applied to the terminals to redirect liquid or air flow. The solenoid valve usually has two or three ports on it:

The main supply port

The normally open (N.O.) port

The normally closed (N.C.) port

Normal means when power is not applied to the solenoid.

Fundamentally the ports are arranged like this:

A solenoid with only two ports would have either a normally open port or a

normally closed port but not both. There are many other configurations for

ports and piloting. The basic operation is only discussed.

Module 6: Solenoids


Understanding Solenoids

Description:

So, when the voltage is not applied, liquid or air can flow between the main supply port and the N.O. port. When voltage is applied, liquid or air can flow between the main supply port and the N.C. port.

How the Solenoid Works

When the voltage is applied to the solenoid coil, an electromagnet is created that moves a valve piston to direct liquid or air flow through the valve. A spring causes the piston to block the N.C. port until the voltage is applied to the coil. Then, the force of the electromagnet pulls the piston, closing the N.O. port and opening the N.C. port.

Module 6: Solenoids


This Concludes

Module 6

Solenoids

Module 6: solenoids


Module 7

Troubleshooting Power and Control Devices

Module 7: Troubleshooting Power and Control Devices


Troubleshooting Faulty Contactors

In this section we will troubleshoot single direction and forward/reverse contactors with an ohm-meter. Each person should be allowed to perform these functions on actual devices.

The single direction contactor contains:

A coil, when energized it will change the states of all contacts

Three main contacts (N.O.) used for switching power to the load (motor)

One auxiliary contact (N.O.) used for the seal-in circuit

To troubleshoot this device out of the circuit, the ohm-meter will be used.

Troubleshooting the coil of a single contactor

The ohmic reading for the coil will vary according to the size of the contactor. In this exercise, the smaller size contactor is demonstrated.

Place the ohm-meter on the A1 and A2 terminals. If the coil is good it should read approximately 100 ohms for a 120v coil, and approximately 6 ohms for a 24v coil.





1L1

3L2

5L3

13NO

2T1

4T2

6T3

14NO

A1 A2

A2

Electrical Representation for a Contactor

L113

14

L3L2

T1 T3T2A2

A1



Troubleshooting the main and auxiliary contacts of a single contactor

The ohmic reading for the contacts should be approximately 0 ohms when closed and open loop (OL) when open.

First, test the contacts for the de-energized operation. Place the ohm-meter on the L1 to T1 terminals. If the contacts are open, the reading should be OL. Continue to check the other two main contacts, L2 to T2, then L3 to T3. All should read OL on the ohm-meter. Then check the auxiliary contacts between terminals 13 and 14. The reading should be OL, also.

To test the contacts for the energized operation, the contactor will need to be manually pressed to simulate the coil energized. Place the ohm-meter on the L1 to T1 terminals. If the contacts are closed, the reading should be 0 ohms. Continue to check the other two main contacts, L2 to T2, then L3 to T3. All should read 0 ohms on the ohm-meter. Then check the auxiliary contacts between terminals 13 and 14. The reading should be 0 ohms, also.





1L1

3L2

5L3

13NO

2T1

4T2

6T3

14NO

A1 A2

A2

Electrical Representation for a Contactor

L113

14

L3L2

T1 T3T2A2

A1


The Forward/Reverse Contactor

It contains:

One coil for the forward direction and one coil for the reverse direction, when the coils are energized they will change the states of all contacts

Three main contacts (N.O.) used for switching power to the forward direction

Three main contacts (N.O.) used for switching power to the reverse direction

One auxiliary contact (N.C.) used for the electrical interlock for the forward direction

One auxiliary contact (N.C.) used for the electrical interlock for the reverse direction


Troubleshooting the coil of the forward/reverse contactor

The ohmic reading for the coil will vary according to the size of the contactor. In this exercise, the smaller size contactor is demonstrated.

Place the ohm-meter on the A1 and A2 terminals for the forward contactor. If the coil is good it should read approximately 100 ohms for a 120v coil, and approximately 6 ohms for a 24v coil. Then place the ohm-meter on the A1 and A2 terminals for the reverse contactor. If the coil is good it should read approximately 100 ohms for a 120v coil, and approximately 6 ohms for a 24v coil.





1L1

3L2

5L3

2T1

4T2

6T3

22NC

A1 A2

A2

1L1

3L2

5L3

2T1

4T2

6T3

A1 A2

A2

21NC

22NC

21NC

Electrical Representation for Fwd Contactor

L121

22

L3L2

T1 T3T2A2

A1

Electrical Representation for Rev Contactor

L121

22

L3L2

T1 T3T2A2

A1



Troubleshooting the main and auxiliary contacts for the forward/reverse contactor


First, test the contacts for the de-energized operation for the

forward contactor. Place the ohm-meter on the L1 to T1 terminals.

If the contacts are open, the reading should be OL.

Continue to check the other two main contacts, L2 to T2.

Then, L3 to T3. All should read OL on the ohm-meter.

Then, check the auxiliary contacts (N.C.) between terminals 21

and 22. The reading should be 0 ohms.


1L1

3L2

5L3

2T1

4T2

6T3

22NC

A1 A2

A2

1L1

3L2

5L3

2T1

4T2

6T3

A1 A2

A2

21NC

22NC

21NC


L121

22

L3L2

T1 T3T2A2

A1


L121

22

L3L2

T1 T3T2A2

A1



Next, test the contacts for the de-energized operation for the reverse contactor. Place the ohm-meter on the L1 to T1 terminals. If the contacts are open, the reading should be OL. Continue to check the other two main contacts, L2 to T2, then L3 to T3. All should read OL

on the ohm-meter. Then check the auxiliary contacts (N.C.)

between terminals 21 and 22. The reading should be 0 ohms.

To test the contacts for the energized operation, the forward

contactor will need to be manually pressed to simulate the coil

energized. Place the ohm-meter on the L1 to T1 terminals. If the

contacts are closed, the reading should be 0 ohms. Continue to

check the other two main contacts, L2 to T2, then L3 to T3. All

should read 0 ohms on the ohm-meter. Then check the auxiliary

contacts (N.C.) between terminals 21 and 22. The reading should

be OL.


1L1

3L2

5L3

2T1

4T2

6T3

22NC

A1 A2

A2

1L1

3L2

5L3

2T1

4T2

6T3

A1 A2

A2

21NC

22NC

21NC


L121

22

L3L2

T1 T3T2A2

A1


L121

22

L3L2

T1 T3T2A2

A1



To test the contacts for the energized operation, the reverse contactor will need to be manually pressed to simulate the coil energized. Place the ohm-meter on the 1L1 to 1T1 terminals. If the contacts are closed, the reading should be 0 ohms.

Continue to check the other two main contacts, 1L2 to 1T2.

Then, 1L3 to 1T3. All should read 0 ohms on the ohm-meter.

Then check the auxiliary contacts (N.C.) between terminals 21 and

22. The reading should be OL.


1L1

3L2

5L3

2T1

4T2

6T3

22NC

A1 A2

A2

1L1

3L2

5L3

2T1

4T2

6T3

A1 A2

A2

21NC

22NC

21NC


L121

22

L3L2

T1 T3T2A2

A1


L121

22

L3L2

T1 T3T2A2

A1


Troubleshooting Faulty Control Relays with Auxiliary Contact Blocks

In this section we will troubleshoot control relays with auxiliary contact blocks with an ohm-meter. Each person should be allowed to perform these functions on actual devices.

The control relay contains:


Four main contacts (2 N.O.) and (2 N.C.) used for switching current and voltage in the control circuit





Troubleshooting the coil

The ohmic reading for the coil will vary according to

the size of the relay. In this exercise, the smaller size

relay is demonstrated.

Place the ohm-meter on the A1 and A2 terminals.

If the coil is good it should read approximately

100 ohms for a 120v coil, and approximately 6 ohms

for a 24v coil.


13NO

21NC

31NC

43NO

14NO

22NC

32NC

44NO

A1 A2

A2

Electrical Representation for a Relay

A2

A143

44

31

32

21

22

13

14



Troubleshooting the main and auxiliary contacts


First, test the contacts for the de-energized operation. Place the ohm-meter on the 13 to 14 (N.O.) terminals. If the contacts are open, the reading should be OL.

Next, place the ohm-meter on the 21 to 22 (N.C.) terminals. If the contacts are closed the reading should be 0 ohms. Continue to check the other contacts, 31 to 32 (N.C.), then 43 to 44 (N.O.).

To test the contacts for the energized operation, the relay will need to be manually pressed to simulate the coil energized. Place the ohm-meter on the 13 to 14 (N.O.) terminals. If the contacts are closed, the reading should be 0 ohms.

Next, place the ohm-meter on the 21 to 22 (N.C.) terminals. If the contacts are open the reading should be OL. Continue to check the other contacts, 31 to 32 (N.C.), then 43 to 44 (N.O.).




Next, clip on the auxiliary contact block.

First, test the contacts for the de-energized operation. Place the

ohm-meter on the 53 to 54 (N.O.) terminals. If the contacts are

open, the reading should be OL. Next, place the ohm-meter on

the 61 to 62 (N.C.) terminals. If the contacts are closed the

reading should be 0 ohms. Continue to check the other

contacts, 71 to 72 (N.C.), then 83 to 84 (N.O.).

To test the contacts for the energized operation, the relay will

need to be manually pressed to simulate the coil energized.

Place the ohm-meter on the 53 to 54 (N.O.) terminals. If the

contacts are closed, the reading should be 0 ohms. Next, place

the ohm-meter on the 61 to 62 (N.C.) terminals. If the contacts

are open the reading should be OL. Continue to check the other

contacts, 71 to 72 (N.C.), then 83 to 84 (N.O.).


13NO

21NC

31NC

43NO

14NO

22NC

32NC

44NO

A1 A2

A2


A2

A143

44

31

32

21

22

13

14

LA1 DN 22

TelemechaniqueET

53 NO 61 NC 71 NC 83 NO

54 NO 62 NC 72 NC 84 NO

TelemechaniqueET

LA1 DN 11

53 NO 61 NC

54 NO 62 NC


Troubleshooting Faulty Control Relays with Timer Blocks (On and Off Delay)

In this section we will troubleshoot control relays with timer blocks with an ohm-meter. Each person should be allowed to perform these functions on actual devices. The ON delay timer will be discussed first.




The ON delay timer contains:

One set of timed contacts that are normally open and will time closed after the relay is energized (N.O.T.C.) and will instantaneously open back up after the relay is de-energized.

One set of timed contacts that are normally closed and will time open after the relay is energized (N.C.T.O.) and will instantaneously close back after the relay is de-energized.






The coil should be tested using the same procedure as before for

the contactors and relays.

Troubleshooting the ON delay timed contacts:

First, test the timed contacts for the de-energized operation. Place

the ohm-meter on the 67 to 68 (N.O.T.C.) terminals. If the contacts

are open, the reading should be OL.

Next, place the ohm-meter on the 55 to 56 (N.C.T.O.) terminals.

If the contacts are closed the reading should be 0 ohms.


13NO

21NC

31NC

43NO

14NO

22NC

32NC

44NO

A1 A2

A2


A2

A143

44

31

32

21

22

13

14

LA2 DT 2

TelemechaniqueET

ON DELAY0.1 - 3s

LA3 DR 2

TelemechaniqueET

OFF DELAY0.1 - 30s

55

56

67

68

NONC

57

58

65

66

NCNO



Next, test the contacts for the energized operation. Place the

ohm-meter on the 67 to 68 (N.O.T.C.) terminals. The reading should

still be OL. Press the timing relay in to simulate the coil energized.

The timed contacts should close after the time dialed on the timer.

When the timed contacts close, the reading should be 0 ohms.

Release the timing relay and the contacts should open immediately.

The reading should go back to OL.

Next, place the ohm-meter on the 55 to 56 (N.C.T.O.) terminals. If

the contacts are closed the reading should be 0 ohms. Press the

timing relay in to simulate the coil energized. The timed contacts

should open after the time dialed on the timer. When the timed

contacts open, the reading should be OL. Release the timing relay

and the contacts should close immediately. The reading should go

back to 0 ohms.


13NO

21NC

31NC

43NO

14NO

22NC

32NC

44NO

A1 A2

A2


A2

A143

44

31

32

21

22

13

14

LA2 DT 2

TelemechaniqueET

ON DELAY0.1 - 3s

LA3 DR 2

TelemechaniqueET

OFF DELAY0.1 - 30s

55

56

67

68

NONC

57

58

65

66

NCNO



The OFF delay timer will be discussed next.




The OFF delay timer contains:

One set of timed contacts that are normally open, will close instantaneously when the timing relay is energized and will time back open after the relay is de-energized (N.O.T.O.).

One set of timed contacts that are normally closed, will open instantaneously when the timing relay is energized and will time back closed after the relay is de-energized (N.C.T.C.).



The coil should be tested using the same procedure as before for the contactors and relays.




Troubleshooting the OFF delay timed contacts

First, test the timed contacts for the de-energized operation before

the timing relay has been energized. Place the ohm-meter on the

57 to 58 (N.O.T.O.) terminals. If the contacts are open, the reading

should be OL. Next, place the ohm-meter on the 65 to 66 (N.C.T.C.)

terminals. If the contacts are closed the reading should be 0 ohms.

Next, test the contacts for the energized then de-energized operation. Place the ohm-meter on the 57 to 58 (N.O.T.O.) terminals. The reading should still be OL. Press the

timing relay in to simulate the coil energized. The timed contacts

should close instantaneously. The reading should be 0 ohms.

Release the timing relay and the timed contacts (N.O.T.O.) should

open after the time dialed on the timer. When the timed contacts

open, the reading should be OL.


13NO

21NC

31NC

43NO

14NO

22NC

32NC

44NO

A1 A2

A2


A2

A143

44

31

32

21

22

13

14

LA2 DT 2

TelemechaniqueET

ON DELAY0.1 - 3s

LA3 DR 2

TelemechaniqueET

OFF DELAY0.1 - 30s

55

56

67

68

NONC

57

58

65

66

NCNO


Troubleshooting Faulty Solenoids

In this section we will troubleshoot solenoids an ohm-meter. Each person should be allowed to perform these functions on actual devices.

The solenoid contains:

A coil, when energized it will change the position of the mechanical valve

The mechanical valve which could be normally open or normally closed, or both.

A mechanical override is supplied with some valves



The ohmic reading for the coil will vary according to the size of the solenoid. In this exercise, the smaller size solenoid is demonstrated.

Place the ohm-meter on the terminals of the solenoid. If the coil is good it should read approximately 100 ohms for a 120v coil, and approximately 6 ohms for a 24v coil.



Troubleshooting Faulty Solenoids

Troubleshooting the mechanical operation of the valve

If the valve is supplied with a mechanical override, operate the override to check the mechanical operation. If the valve is not supplied with a mechanical override, the appropriate voltage for the coil should be applied to the solenoid coil to check the mechanical operation.



This Concludes

Module 7

Troubleshooting Power and Control Devices


Presentation : IMS – Tech Managers ConferenceAuthor : IMS StaffCreation date : 08 March...

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Transcript of Presentation : IMS – Tech Managers ConferenceAuthor : IMS StaffCreation date : 08 March...