Standard AC Motors

Construction of AC MotorsThe following figure shows the construction of a standard ACmotor. Bracket: Die-cast aluminum bracket with a machined finish,

press-fitted into the motor case. Stator: Comprised of a stator core made from laminated

silicon/steel plates, a polyester-coated copper coil andinsulation film.

Motor Case: Die-cast aluminum with a machined finish inside. Rotor: Laminated silicon/steel plates with die-cast aluminum. Output Shaft: Available in round shaft and pinion shaft types.

The metal used in the shaft is S45C. Round shafts have a shaftflat (output power of 25 W or more), while pinion shafts undergoprecision gear finishing.

Ball Bearing Lead Wire: Lead wires with heat-resistant polyethylene coating. Painting: Baked finish of acrylic resin or melamine resin.

Brake Mechanism of the Reversible MotorA reversible motor has a simple, built-in brake mechanism (frictionbrake) at its rear. This mechanism is provided for the followingpurposes:a. To improve the instant reversing characteristics by adding a

friction loadb. To reduce overrun

The brake mechanism is constructed as shown in the figure above. The coil spring applies constant pressure to allowthe brake shoe to slide toward the brake plate.This mechanism provides a certain degree of holding brake force,but the force is limited due to the mechanisms structure, asdescribed above. The brake force produced by the brakemechanism of an Oriental Motor reversible motor is approximately10% of the motors output torque.

Coil SpringEnd Plate

Brake ShoeBrake Plate

Bracket

Output Shaft

Motor Case Painting

Stator

Rotor

Ball Bearing

Lead Wire

Induction Motor Speed Torque Characteristics

The figure below shows the motors characteristics of speed andtorque.

Under conditions of no load, the motor rotates at a speed close tosynchronous rotation. As the load increases, the motors speeddrops to a level (P) where a balance is achieved between load andmotor torque (Tp). If the load is further increased and reaches point M, the motor cangenerate no greater torque and stops at point R. In other words,the motor can be operated in a stable range between M and O,while the range between R and M is subject to instability. Induction motors are available in two types: single-phase(capacitor run) and three-phase induction motors. With the single-phase motor, the starting torque is generally smaller than theoperating torque, while the three-phase motor features a relativelygreater starting torque.

Reversible Motor Speed Torque Characteristics

The reversible motor is a capacitor-run, single-phase inductionmotor that features the same characteristics as an inductionmotor, as described above. However, the reversible motor features a higher starting torquethan an induction motor in order to improve the instant reversingcharacteristics.

Torque

Induction Motor

SpeedTorque Characteristics

Speed [r/min]

Torque

Speed (r/min)

Three-Phase motors

Torque

Speed (r/min)

Single-Phase motors

Torque

Speed

TM

TS

TP P

M

O

R

Unstable Region Stable Region

G-18 ORIENTAL MOTOR GENERAL CATALOGUE

TechnicalReference

Torque Motor Speed Torque Characteristics

The figure below shows the torque motors characteristics ofspeed and torque. The speed and torque characteristics of torquemotors differ from those of induction motors or reversible motors.As the graph shows, they have special torque characteristics(torque is highest at zero speed and decreases steadily withincreasing speed), so they can provide stable operation throughthe entire speed range, from starting to no-load speed. The torquegenerated during reversal of the motor is a large positive torque inthe same direction as the rotational magnetic field. When themotor is locked by the load and the motor is rotated opposite thedesired direction, this torque acts as a force (braking force) toinhibit the motor from rotating backwards.

CapacitorOriental Motors single-phase AC motors are permanent splitcapacitor types. Capacitor-run motors contain an auxiliary windingoffset by 90 electrical degrees from the main winding. The capacitoris connected in series with the auxiliary winding, causing the currentin the auxiliary winding to lag the current in the main phase.Motors generally employ vapor-deposition electrode capacitors foruse with electrical equipment, as specified in JIS C 4908. Thistype of capacitor, which uses a metallized paper or plastic film asan element, is also known as a self-healing (SH) capacitor, because of the self-healing property of the capacitor element.Although most of the previous capacitors used paper elements,the plastic film capacitor has become a mainstream model inrecent years due to the growing demand for compact design.

CapacitanceThe use of a capacitor with a different capacitance may causeexcessive motor vibration and heat generation or may result intorque drops and unstable operation. Be sure to use the capacitorsupplied with the motor. The capacitors capacitance is expressedin microfarads (F).

Rated VoltageUsing the capacitor at a voltage level exceeding the rated voltage maysignificantly reduce the capacitors service life. Be sure to use thecapacitor supplied with the motor. The rated voltage of the capacitor isexpressed in volts (V). The capacitors rated voltage is indicated onthe surface of the capacitor case. Take proper precautions, since thecapacitors rated voltage is different from that of the motor.

Rated Conduction TimeThe rated conduction time is the minimum design life of the capacitorwhen operated at the rated load, voltage, temperature and frequency.The standard life expectancy is 25,000 hours. We recommend thatthe capacitor be replaced after the rated conduction time.Consider providing a separate protection measure to prevent theequipment from being negatively influenced in the event of capacitorfailure.

Braking Region

Stable Region

Speed

100 VAC

NsNs

60 VAC

Torque

0

Stab

le R

egio

n of

Indu

ctio

n M

otor

Safety Feature of CapacitorThe UL-recognized capacitors, supplied with the motors, areequipped with a safety feature that allows for safe and completeremoval of the capacitor from circuits to prevent smoke and/or firein the event of a dielectric breakdown. Oriental Motor usescapacitors with UL-recognized safety features that have passedthe UL810 requirement of the 10,000-A fault current test.

Temperature Rise in Standard ACMotors

Temperature Rise in MotorsWhen a motor is operating, all energy loss from the motor istransformed into heat, causing the motors temperature to rise. Induction motors: Induction motors, which are rated for continuous

duty, reach the saturation point of temperature rise after two orthree hours of operation, whereupon its temperature stabilizes.

Reversible motors: Reversible motors (30 minute rating) reachtheir limit for temperature rise after 30 minutes of operation. Thetemperature will increase further if operation continues.

Measuring the Temperature Rise The following is a description of the methods Oriental Motor usesfor temperature measurement and for the determination of amotors maximum allowable temperature rise.

Thermometer Method The temperature at which the temperature rise during motoroperation becomes saturated is measured using a thermometer orthermocouple attached to the center of the motor case. Thetemperature rise is defined as the difference between the ambienttemperature and measured temperature.

Resistance-Change MethodIn the resistance-change method, the winding temperature ismeasured according to the change in resistance value. A resistancemeter and thermostat is used to measure the motors windingresistance and ambient temperature before and after operation,from which the temperature rise in the motor windings is obtained.

Overheating Protection DevicesIf a motor operating in run mode locks due to overload or the inputcurrent increases, the motor's temperature rises abruptly. If themotor is left in this state, the performance of the insulation withinthe motor may deteriorate, reducing its service life and, in extremecases, scorching the winding and causing a fire. In order to protectthe motor from such thermal abnormalities, UL, CSA, EN and IECstandard motors from Oriental Motor are equipped with thefollowing overheating-protection devices.

Thermally Protected MotorsMotors with a frame size of 70 mm sq., 80 mm sq., 90 mm sq. or104 mm sq. contain a built-in automatic-return type of thermalprotector. The construction of a thermal protector is shown in thefigure below.

The thermal protectors employ a bimetal contact with pure silverused in the contacts. Pure silver has the lowest electricalresistance of all materials and has thermal conductivity secondonly to copper.

Bimetal Contact

Pure-Silver Contact PointsLead Wires

Fig.1 Structure of a Thermal Protector

G-19

TechnicalReference

Service Life

Motor andFan Sizing

StandardAC Motors

BrushlessDC Motors

SteppingMotors

Gearheads

LinearMotion

Fan Motors

G-20 ORIENTAL MOTOR GENERAL CATALOGUE

TechnicalReference

Operating temperature of thermal protectorOpen130C5C (the operating temperature varies

depending on the model, e.g., BH Series: 150C5C)Close82C15C (the operating temperature varies

depending on the model, e.g., BH Series: 96C15C)The motor winding temperature, where the thermal protector isworking, is slightly higher than the operating temperature listed above.

Impedance Protected Motors Motors with frame sizes of 60 mm sq. or less are equipped withimpedance protection.Impedance-protected motors are designed with higher impedancein the motor windings so that even if the motor locks, the increasein current (input) is minimized and temperature will not rise abovea certain level.

Speed Control Methods of Speed Control Motors

The basic block diagrams and outline of the control methods areshown below. AC speed control motors employ a closed-loopcontrol system.

AC Speed Control Motors

The speed setting voltage is supplied via a potentiometer. The motor speed is sensed and the speed signal voltage is supplied. The difference between the speed setting voltage and speed

signal voltage is output. A voltage determined by the output from the comparator is

supplied to the motor so that it will reach the set speed.

Speed Torque Characteristics of Speed Control Motors

AC Speed Control MotorsThe speed-torque characteristic line shown in the figure below istypical for all AC speed control motors.

150010005000

1800

1.0

2.0

3.0

4.0

5.0

0.1

0.2

0.3

0.4

0.5

Torq

ue[k

gfcm

]

Torq

ue[N

m]

Speed [r/min]

0

Permissible Torque when Gearhead is Attached

110/115 VACSafe-Operation Line

MSS425-401WU-

Volta

ge-c

ontro

l circ

uit

Com

para

tor

Power supply

Potentiometer

Motor

Speed control pack

Capacitor

Tachogenerator

1

2

3

4

Safe Operation Line and Permissible TorqueWhen Using a Gearhead

Input power to the speed control motor varies with the load andspeed. The greater the load, and the lower the speed, the greateran increase in motor temperature.The previous graph displays the relationship between the speedand torque characteristics of an AC speed control motor. The lineis referred to as the safe operation line, while the area below theline is called the continuous operation area.The safe operation line, measured according to motortemperature, indicates its operational limit for continuous usagewith the temperature level below the permissible temperature. (Inthe case of a reversible motor, it is measured via 30-minuteoperation.)Whether the motor can be operated at a specific torque and speedis determined by measuring the temperature of the motor case. Ingeneral, if the motor's case temperature is 90C or below,continuous motor operation is possible, considering the insulationclass of motor winding. It is recommended that the motor be usedunder conditions that keep the motor temperature low, since themotor life is extended with lower motor temperature. When using a gearhead, be aware that it is necessary to operatebelow the maximum permissible torque. If the actual torquerequired exceeds the maximum permissible torque, it may damagethe motor/gear and/or shorten its life.

Variable Speed Range (Speed Ratio) and Load Factor

When the ratio of minimum speed and maximum speed of a speedcontrol motor is given as the motors speed ratio, the speed ratioincreases to as much as 1:18 in a range where the load factor(ratio of load torque to starting torque) is small (see the 50% loadfactor range in the following diagram). This widens the motorsrange of operation. If the load factor is high, the speed ratiobecomes low.

Load Factor and Speed RatioUnder conditions of actual use, a motor is often used incombination with a gearhead. The following example assumessuch a configuration.The following table shows the continuous operation range andspeed ratio of the US Series at load factors of 50% and 70%,respectively, as read from the diagram. Although the speed ratio is1:18 when the load factor is 50%, it decreases when the load factoris 70%. As shown, generally AC speed control motors do not have awide operation range (when the load factor is high). To operate yourmotor over a wide speed range, choose a type that offers highstarting torque (i.e., a motor with the next larger frame size).With a brushless DC motor, the operation range remains wideregardless of the load factor, as indicated by the dotted line.

Continuous Operation Range

5070

1550

Minimum Speed [r/min]

267267

Maximum Speed[r/min]

Approx.1:18Approx.1:5

Speed RatioLoad Factor[%]

100 200 300(267)Speed [r/min]

0

2

3

4

5

1

0

Torq

ue [N

m]

US590-501U5GU6KFBL5120AW-10

Speed-Torque Characteristics (US590-501U/5GU6K)

Load Factor 70% Approx. 1:5

Load Factor 50% Approx. 1:18

G-21

TechnicalReference

Service Life

Motor andFan Sizing

StandardAC Motors

BrushlessDC Motors

SteppingMotors

Gearheads

LinearMotion

Fan Motors

Speed Ratio with/without GearheadBecause the speed control motors continuous operation range islimited by motor temperature, the continuous operation range willwiden if the motors efficiency of heat dissipation is improved andthe temperature rise is curbed. In that case, a motor with agearhead will have a higher speed ratio than a motor used aloneat the same load factor of 70%, as shown in the diagram below.The speed ratio will increase further if the motor with a gearhead isinstalled in the equipment, since the equipment itself serves as aheat sink.

Due to the aforementioned advantage of heat dissipation, when amotor is installed in equipment it can often be operated at variablespeeds with a speed ratio of 1:18, as long as the load factor doesnot exceed 70%.

Speed Ratio when a High Ratio Gearhead is UsedSince the starting torque is also limited by the maximumpermissible torque of the gearhead, the load factor of a gearheadwith a high gear ratio is determined by the load torque with respectto the maximum permissible torque of the gearhead.In the previous example, a gearhead with a gear ratio of 1:6 wasused. The diagram below shows what happens when a gearheadwith a gear ratio of 1:120 is used.

The maximum permissible torque of the 5GU120K, which has agear ratio of 1:120, is 20 Nm (200 kgfcm). The speed ratios at50% and 70% load factors are shown in the table below:

The table above demonstrates that high speed ratios can beobtained by combining a motor with a gearhead having a highgear ratio, in which case the load factor is one of minor concern.

Continuous Operation Range

5070

0.750.75

Minimum Speed [r/min]

13.313.3

Maximum Speed[r/min]

Approx.1:15Approx.1:15

Speed RatioLoad Factor[%]

US590-501U5GU120KFBL5120AW-200

1:10

5 10 (13.3) 15Speed [r/min]

0

30

20

10

0

Torq

ue [N

m]

Speed-Torque Characteristics with a High Gear Ratio

Load Factor 70% Approx. 1:18

Load Factor 50% Approx. 1:18

Motor: US590-501UGearhead: 5GU6K

With GearheadInstallation in Equipment

500 1000 1600 1800Speed [r/min]

0

1.0

0.8

0.6

0.4

0.2

0

Torq

ue [N

m]

1500

Without GearheadWith Gearhead

Load Factor 70% Approx. 1:2.5

Approx. 1:5Approx. 1:18

Construction of an ElectromagneticBrake

An electromagnetic brake motor is equipped with a power offactivated type electromagnetic brake.

As shown in the figure below, when voltage is applied to themagnet coil, the armature is attracted to the electromagnet againstthe force of the spring, thereby releasing the brake and allowingthe motor shaft to rotate freely. When no voltage is applied, thespring works to press the armature onto the brake hub and holdthe motors shaft in place, thereby actuating the brake.

Magnet Coil

Spring

Brake Hub

Armature

Brake Lining

G-22 ORIENTAL MOTOR GENERAL CATALOGUE

TechnicalReference

Glossary Ratings

Ratings Motor rating limitations pertaining to temperature rise are dividedinto two categories: continuous and short-term ratings. Theseestablish working limitations on output, as well as on voltage,frequency and speed (r/min), and are known as rated output, ratedvoltage, rated frequency and rated speed (r/min).

Continuous and Limited Duty Ratings The period during which output can continue without abnormalityis called a rating period. When continuous operation at ratedoutput is possible, it is known as a continuous rating. Whenoperation at rated output is possible only for a limited period, it isknown as the short-term rating.

Output Power

Output PowerThe amount of work that can be performed in a given period oftime is determined by the motor's speed and torque. Each motor ismarked with a rated output value. Output power is expressed inwatts and in horsepower.

Output Power [watts]1.04710-1TN1 HP746 Watts

where: 1.04710-1 : ConstantT [Nm] : TorqueN [r/min] : Speed

Rated Output PowerWhen optimal characteristics are achieved at the rated voltageand frequency in continuous operation, the motor is said to beoperating at its rated output. The speed and torque that producethe rated output are called the rated speed and rated torque.Generally, the term output refers to rated output.

Torque

Starting Torque This term refers to the torque generated the instant the motorstarts. If the motor is subjected to a load greater than this torque, itwill not operate.

Stall Torque This is the maximum torque under which the motor will operate ata given voltage and frequency. If a load greater than this torque isapplied to the motor, it will stall.

Rated Torque This is the torque created when the motor is continuouslyproducing rated output at the rated voltage and frequency. It is thetorque at rated speed.

Static Frictional TorqueStatic frictional torque is the torque output required to hold a loadwhen the motor is stopped by an electromagnetic brake or similardevice.

Permissible TorqueThe permissible torque is the maximum torque that can be usedwhen the motor is running. It is limited by the motors rated torque,temperature rise and the strength of the gearhead used with themotor.

SpeedTorque Characteristics

Speed

Synchronous SpeedThis is an intrinsic factor determined by line frequency and thenumber of poles. It is calculated according to the following formula,and is normally indicated in r/min.

NS : Synchronous speed [r/min]f : Frequency [Hz]P : Number of poles120 : Constant

For example, for a four-pole motor with a line frequency of 50 Hz,the synchronous speed will be:

See in the figure above.

No-Load SpeedThe speed of induction or reversible motors under no-loadconditions is lower than synchronous speed by 2 to 20 percent.See in the figure above.

Rated Speed This is the appropriate speed of the motor at rated output. Fromthe standpoint of utility, it is the most desirable speed. See inthe figure on above.

Slip The following formula is one method of expressing speed:

NS: Synchronous speed [r/min]N: Speed under a given load [r/min]

In the case of a four-pole, 50 Hz induction motor operated with aslip of S = 0.1, the speed under a given load will be:

Overrun

Overrun This is the number of excess rotations the motor makes from theinstant the power is cut off to the time that it actually stops. It isnormally indicated either by an angle or by revolutions.

Gearhead

Gear Ratio The gear ratio is the ratio by which the gearhead reduces themotor speed [r/min]. The speed at the gearhead's output shaft isone over the gear ratio times the motor speed.

120504

N= (10.1) =1500 (10.1) =1350 [r/min]

NsNNs

S= N=Ns (1S)or

120504

Ns= =1500 [r/min]

120fP

Ns= [r/min]

Torq

ue [Nm

]

Speed [r/min]

1

2

3

456

: Starting torque: Stall torque: Rated torque: Synchronous speed: No-load speed: Rated speed

G-23

TechnicalReference

Service Life

Motor andFan Sizing

StandardAC Motors

BrushlessDC Motors

SteppingMotors

Gearheads

LinearMotion

Fan Motors

To enable the gearheads output shaft to operate at the samerotational speed regardless of the different motor speeds producedin the 50 Hz and 60 Hz areas, the gearhead ratios are available intwo different sequence types: 1) 1:3, 1:5, 1:7.5, 1:12.5, 1:15 ... and2) 1:3.6, 1:6, 1:9, 1:15 and 1:18 (the latter ratios increasing by 20percent for the 60 Hz area).Using a gear ratio of 1:3 for the 50 Hz area and a ratio of 1:3.6 forthe 60 Hz area will produce roughly the same rotational speed atthe gearhead's output shaft.All gearheads may be used in both the 50 Hz and 60 Hz areas.

Maximum Permissible Torque This is the maximum load torque that can be applied to thegearhead. It is dependent upon such mechanical strength factorsas the size and construction of the gears and bearings, and thusvaries according to the gearhead type and ratio.

Service FactorThis is a coefficient used to estimate the life of a gearhead. These values are determined in accordance with the results ofservice life tests under various loads and conditions of use.

Transmission EfficiencyThis is the efficiency of transmission when the torque is increasedwith the gearhead attached. It is expressed as a percentage (%)and is determined by the friction in the gears and bearings used inthe gearhead and the resistance of the lubrication grease. Transmission efficiency is usually 90% for one stage of reductiongears, and is 81% for two-stage gearheads. As the reduction ratioincreases, the number of gear stages increases, with aconsequent reduction in the gear efficiency to 73% and 66%,respectively, for each gear stage added.

Overhung LoadThis is a load on the gearheads output shaft in the radial direction.The maximum overhung load on a gearhead shaft is called thepermissible overhung load, and it varies with the gearhead typeand distance from the shaft end. This is equivalent to tensionunder belt drive.

Thrust LoadThis is the load that is placed in the direction of the gearheadsoutput-axis shaft. The maximum thrust load on the gearhead iscalled the permissible thrust load, which differs by the type ofgearhead.

Others

CW, CCWThis shows the direction of motor rotation. CW is clockwise as seen from the output shaft side, while CCW iscounterclockwise.

Gearhead

Overhung Load

Thrust Load

G-24 ORIENTAL MOTOR GENERAL CATALOGUE

TechnicalReference

Q&AQ1I may have to put the motor in an environment of 20C to30C during transport. Will this create a problem?A1Extreme changes in temperature may lead to condensation withinthe motor. Should this occur, parts may rust, greatly shortening theservice life. Take measures to prevent condensation.

Q2Can the motors be shipped through tropical climates?A2No. When the humidity and temperature differences within thecargo space of ships and airplanes are severe, the insulation maydeteriorate due to condensation. Successful countermeasures areto ship the motors packed in sealed containers or bags containingde-oxygenating material.

Q3The motor gets extremely hot. Is this all right?A3The internal losses generated when the motor converts electricalenergy to rotational movement becomes heat, making the motorhot. The motor temperature is expressed as the ambienttemperature plus the temperature rise caused by losses within themotor. If internal losses within the motor is 50C and the ambienttemperature is 30C, the surface of the motor will be 80C. This isnot abnormal for a small motor.The maximum temperature limits for the motor are 120C or130C on the motor windings and 90C or 100C on the surfacewhose temperature is lower than the motor's interior by 10C to30C.Be sure to use the motor with the motor case temperature notexceeding 90C, so as not to shorten its useful life.

Q4Will large fluctuations in power supply voltage affect themotor?

A4The torque produced by the motor is affected by changes in powersupply voltage. The torque the motor produces is proportional toroughly twice the power supply voltage. For example, if the voltageof a motor rated at 100 VAC fluctuates between 90 VAC (90%)and 110 VAC (110%), the torque produced will vary between 80%and 120%. When using motors under large power voltagefluctuations, remember that the torque produced will vary, soselect a motor that provides a sufficient margin.

Q5Can a single-phase motor be driven using a three-phasepower supply?A5A single-phase 200 VAC motor can be driven using a three-phasepower supply. Use two of the three phases as the source of powersupply. The same voltage can be obtained by combining two ofthe u, v, and w windings in one of the following patterns: U-V, U-Wand V-W.When using a number of motors, be sure to connect them to thepower supply so that a balanced supply of power is achieved fromeach phase.

Q6Can a reversible motor be used as an induction motor if thebrake shoes are removed?

A6A reversible motor is not simply an induction motor with a simplebraking mechanism added. The ratio of coils between the primarycoil and the secondary coils in a reversible motor is different fromthat of an induction motor. Although a simple brake mechanism isadded to the rear of the motor, the capacitance is also increasedto increase starting torque. This means that if only the brakemechanism is removed, the reversible motor will not be usable ata continuous rating like an induction motor; it will simply lose itsholding power and its reversing characteristics will be reduced.

Q7What does it mean to say that a reversible motor is rated for30 minutes?

A7Reversible motors require a larger input power than inductionmotors to increase the starting torque and improve the instantreversing characteristics. This means that the losses are higherand the temperature rises more during continuous operation. Ifoperated continuously, the motor will burn out. It is designed toprovide maximum performance if operated for no more than 30minutes continuously.

Q8Can the speed of induction motors and reversible motors bechanged?A8The speed of single-phase (AC) induction and reversible motors isdetermined by the power-supply frequency.The electric power supplied to commercial power sources is ratedat either 50 Hz or 60 Hz in Japan. The motor's speed cannot bemodified in a 50 Hz/60 Hz site.To change the speeds of induction and reversible motors, thepower-supply frequency can be changed using inverter control orgears and pulleys.If your application requires a change in speed, we recommend abrushless DC motors or AC speed control motors.

G-25

TechnicalReference

Service Life

Motor andFan Sizing

StandardAC Motors

BrushlessDC Motors

SteppingMotors

Gearheads

LinearMotion

Fan Motors

Q9Can instant reversal of a reversible motor be implementedusing a SSR (solid state relay)?A9When instant forward/reverse operation is controlled with an SSR,the SSR characteristics can cause shorts in the circuit. Time mustbe allowed between switching from the SSR for clockwise rotationto the SSR for counterclockwise rotation.If your equipment requires that the direction of a reversible motorbe changed instantaneously, SB50 will provide a non-contactmeans for controlling instant forward/reverse operation. Refer toPage A-149 for details.

Q10The connection diagrams shows that a capacitor must beconnected. Why is this necessary?A10Most of Oriental Motor standard compact AC motors fall within thebroad group of single-phase induction motors are capacitor-runmotors. To run an induction motor, a rotational magnetic field mustbe created. Capacitors perform the role of creating a power supplywith the phase shift that is required for creating such a rotationalmagnetic field. Three-phase motors, by contrast, always supplypower with different phases, so they do not require capacitors.

Q11Can I use a capacitor other than the one that comes with themotor?

A11The capacitor that comes with the motor has a capacitance thatwas selected to work optimally with the motor. When anothercapacitor is used, it should be a motor capacitor with the samecapacitance and rated voltage as the capacitor that comes withthe motor. Electrolytic capacitors may not be used.

Q12We wired the induction motor according to the wiring diagram,but it does not move. When we turned the shaft by hand, itstarted to move in the direction we turned it. What could be thecause of this?

A12In order to turn a single-phase induction motor, it is necessary touse a capacitor to create two power supplies with different phasesto obtain the rotating magnetic field. The problem describedoccurs, if the capacitor is not properly connected. Check for a cutline or contact defect near the capacitor section. The way to checkis to measure the voltage across the capacitor terminals andcheck whether or not it is at least 1.5 times the power supplyvoltage. If not, the capacitor may not be working properly.

Q13Why do some gearheads output in the same direction as themotor while others output in the opposite direction?A13Gearheads reduce the motor speed by 1:3 to 1:180. (Gear ratiosvary by model.) They do not, however, reduce the speed with asingle gear stage, but with several. The number of gear stagesdepends on the gear ratio, so the direction of output shaft rotationdiffers.Rotating in motor axis direction Rotating opposite of motor axis direction

Gearhead output shaft Gearhead output shaftMotor pinion Motor pinion

Q14Can gearheads be used to reduce the motor speed to1/18,000? A14Yes. A gearhead with a gear ratio of 1:180 must be connected totwo decimal gearheads with a gear ratio of 1:10. The permissibletorque is the same as if the 1:180 gearhead were used alone.Longer mounting screws must be used.

Q15Do gearheads require oiling?A15Oriental Motor lubricates the surface of gears in gearheads withgrease. Oiling is not required.

MotorDecimal gearheads

Gearhead