A Regal Brand

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VD

Totally Enclosed Fan CooledLow Voltage Ac Cage InductionMotors

MARATHON Electric introduces VD series motorstailor made for inverter drives having enhanceddielectric strength and adequate thermal margin suitablefor variable speed application.PWM technology involving high switching frequencyIGBT drive has enabled AC induction motors to beoperated as variable speed drives. However, therehad been a documented increase of premature windingfailure for standard general purpose motors whenoperated with inverter drives.High and steep front voltage spikes (dV/dt) producedby latest generation IGBT drives associated with thephenomenon of voltage wave reflection due to longercable length imposes stress on the motor windingresulting rapid ageing and deterioration of insulationsystem.

The rating for Variable speed motors need to beselected based on following aspects-● Heating due to harmonic content of inverter

waveform.● Reduced ventilation due to low speed operation.● Constant torque/Constant Power/ Variable torque

requirement of load.● Other limiting factors eg. maximum permissible

motor speed, ambient temp. altitude etc.While variable speed drives provide highest energysaving for variable torque (Centrifugal pump, fan)applications, for constant torque and constant powerapplication, Variable speed drives offer significantprocess control improvements. Basic inverters permitoperation over a typical 20:1 speed range. Withclosed loop vector control the effective range may beincreased to 1000:1.

Principle of OperationSo far DC motor had been the only choice whereprecise torque and speed control was required. ACinduction motor has no direct control over the currentsof the rotor, so a rapid transient response from onesteady state to another had been a problem. Throughhighly sophisticated motor modeling algorithms andinternal circuitry, the vector control drive has solvedthis problem. With quick instantaneous changes in thestator current, quick instantaneous changes occur inthe rotor current. Vector drive manipulates the motortorque by indirectly controlling the current of the rotorthrough the stator windings. Calculating and quantifyingthe corresponding changes in the rotor current is the

Standards

VD series motors are manufactured to thefollowing national and International standards.

Standards India InternationalIEC NEMA

Dimension IS 1231 IEC60072-1 MG1-PT.4Protection IS4691 IEC60034-5 MG1-1.26BMounting IS2253 IEC60034-7 MG1-PT.4Performance — IEC/TS-60034-17/ MG1-Pt30 & 31

IEC/TS-60034- 25Cooling IS6362 IEC 60034-6

Table 3

1

genius of the vector drive.Some vector control drives also require positionfeedback from a shaft mounted encoder. Vector Controlassociated with space vector modulation techniquesfor voltage source inverters have enabled to achievehigh quality current and torque response using inductionmotor drives.

Mostly voltage source inverters employing PWM controlis employed for variable speed drives. PWM voltagesource inverters employ a converter section comprisingof a rectifier bridge supplying power to DC link filterwhich operates at a nominal constant voltage. The DClink supply is fed to the inverter section converting DCto AC through a 3 Phase bridge comprising highspeed switching devices (IGBT) producing a variablevoltage variable frequency sinusoidal supply for themotor.Inverters would deliver a proportional voltage andfrequency up to base voltage (V1) and base frequencyf1 (Corresponding base speed n1) set by the user.Beyond base frequency, voltage (V1) remains fixedas per available supply voltage up to maximumpermissible frequency f2 (Corresponding speed n2)and f3 (Corresponding speed n3). Motor output ratingbecomes proportional to frequency up to f1 and motoroutput remains constant beyond f1 up to f2 and motor

operates with reduced output upto maximumpermissible frequency f3. f2 is normally decided bylimiting motor temp. rise owing to higher iron lossat higher frequency and high windage loss (Selfcooled motors) and minimum P.O.T requirement. f3is decided mainly based on max. speed limitationimposed by bearing and rotor assembly. Operatingflux of the motor remains constant up to base frequency(f1) by keeping V/f as constant. However, at lowfrequencies (<10Hz.) it is necessary to provide voltageboost to maintain required torque.

Fig. 1Typical sine wave generated by inverter pulse

Speed (n) Torque (T) Power (P) Voltage (V)

o – n1 Constant pαn V/f

1n1 – n2 Tα – Constant V1

n

1 1n2 – n3 Tα – Pα – V1

n2 nTable 1

Note :n1 = Speed at base frequency (f1)n2 = Maximum speed at max. motor torquen3 = Maximum Speed at reduced output

Power

o n1 n2 n3

Speed

Fig. 3

Pn

Voltage

Frequencyf1 f2 f3

V1

Fig. 4

VD series motors meet in general MG1-Pt.31requirement for “Definite Purpose Inverter Fed Motors”.VD series motors up to 460V base voltage aredesigned for —● Peak voltage -1600V Max● Carrier Switching Frequency : 3-5Khzs● Voltage rise time>0.1 microsec.● Total harmonic distortion<2.5%Motors with still higher base voltage up to 690V aredesigned suitable for still higher peak voltage.

Supply Voltage and frequencyStandard motors are suitable for operation for a mainssupply of 3 Phase, 415V+/-10%, 50Hz.+/-5% .However, motors can be offered for any base voltagefrom 200Volt to 690Volts.

ProtectionVD series motors are provided with IP55 degree ofprotection as standard. IP56 degree of protection canbe provided on request.

DutyStandard VD series motors are designed for S1 duty.VD series crane duty motors suitable for S4/S5 dutyratings are available as a seperate range. Motor tosuit other duty conditions may be offered on request.

Insulation and Temp. riseThe motors are designed suitable for 45°C ambienttemperature and provided with class F insulation withtemp. rise limiting to class B limit. Research have shownthat thermal margin enhances dielectric performanceof inverter fed motors significantly. Class H insulationmay be offered on request. Motor re-rating factor dueto ambient temperature and altitude is indicated inthe motor selection chart. Apart from many otherspecific design considerations, VD series motors areprovided with special insulation system to withstandvoltage stresses imposed by IGBT based drivescomprising of the following.● Special grade of wire insulation depending on

motor rating● Vacuum impregnation /Multi dip treatment● Tropicalisation treatment● Phase separator/Overhang tape

CoolingStandard motors are suitable for operation with shaftmounted fan with standard IC411 cooling configuration.Various forms of cooling is given below.

Rating

Construction Frame Size Output Range

Aluminum VDA63 –VDA 180L 4 Pole : 0.12KW-18.5KWBody 6 Pole : 0.37KW-15KW

VD80 – VD 355L 4 Pole : 0.55KW- 280KW6 Pole : 0.37KW-250KW

Cast Iron VK355S – VK400L 4Pole :180KW-315KWBody 6 Pole :160KW-280KW

VDC315F-VDC355F 4 Pole : 350KW-560KWTable 2

Fig. 2Typical Voltage Source PWM inverter

MAINSIN

DC LINKCAPACITOR

DC LINK CHOKE

SUPPLY CONVERTOR MACHINE CONVERTOR

OU

TPU

T

2

Frame Supply Current Input Increase in Overall Length Air DeliveryAmps Watts Without Encoder mm CMH

VFD132 165 300VFD160

0.2 80170 400

VFD180 190 500VFD200

0.3 132190 600

VFD225 3PH,415V,50HZ 190 800VFD250 180 1000VFD280

0.82 372180 2000

VFD315 215 3000VFD355 1.0 500 355 4000

Table 6

Code ArrangementIC411 Totally Enclosed Fan Cooled. Motor

cooled by its own shaft driven externallymounted fan. Cooling effect reduces withreduction of speed. Overspeedingincreases Windage loss and noise level

IC410 Totally Enclosed Non ventilated (TENV).Free convection (self cooling), no externalmounted fan,

IC418 Totally enclosed Air Over Motor cooledby airstream. Cooling effect reduces withreduced airstream velocity.

IC 416 Totally enclosed Force cooled. Motorcooled by independent fan.Constantcooling throughout speed range.

Table 4

Consideration for Variable speed operationVariable speed drives are used for operation both atlow and high speed. Cooling for variable speedmotors gets affected while operating at lower speedwhereas during high speed operation windage losses,bearing lubrication, increase in noise level, increasedtemp. due to shaft seals if any require special attention.Max. permissible speed for standard VD series motoris indicated in Table 5. At low speed (Below 10Hz.)loss distribution changes substantially which may leadto higher surface temp. Temp. rise near bearinglocation should be periodically checked to ascertainthat they are within limit. For sustained operation atlow speed separate Force ventilation (FV) unit isrecommended. FV unit is also used to restrict windageloss and motor noise when the motor runs frequentlynear to highest permissible operating speed of thebearing system. For applications necessitating higherspeed than 80Hz. refer to us.

Frame Size Maximum permissible R.P.M.80-160 6000180 4800200 4500225-280 3600315 - 2 Pole 3600315-4,6 Pole 3000355-2 pole 3600355-4, 6 Pole 2500

Table 5

Force Ventilation UnitForce ventilation unit replaces integral shaft mountedfan with an independently mounted separately excitedmotor driven fan. The unit provides constant airflowto the drive motor throughout speed range. TotallyEnclosed Air over motor /TEFC motor, depending onthe design of FV unit, is provided to drive theindependent fan. Fan motor rating depends on therating and size of drive motor. Specially designedaxial flow fan with optimized air delivery, low noiselevel and minimum power input is provided.Following table provides brief specification of standardFV unit. However, FV unit specification is normallyreviewed with drive requirement and is subject tochange as required.

BearingMetric size Ball and Roller bearings are used. Doublesealed bearings are provided with high temp. greasesuitable for operation upto 110°C. Grease reliefarrangement is provided for motors having re-greasing facility.

Frame Drive Non Drive Size End Bearing End Bearing80 6204ZZ 6204ZZ90 6205ZZ 6204ZZ100 6206ZZ 6205ZZ112 6206ZZ 6205ZZ132 6208ZZ 6207ZZ160 6309ZZ 6209ZZ180 6310ZZ 6210ZZ200 6312 6310ZZ225 6313 6313250 6314 6313280 6317 6314

315 S/M-2 pole 6317 6316315S/M- >4 Pole 6319 6316315M/L- 2 Pole 6317 6317315M/L- >4 Pole 6319 6319

(For bigger sizes refer to MARATHON Electric)

Table 7

Bearing CurrentDepending on motor size and supply voltage rating,bearing current may be generated owing to shaftvoltage caused by high dV/dT common mode voltage(CMV) and motor parasitic capacitance. Normallybearing fluting caused by such bearing currents arenoted from motor rating 110KW upwards. For framesizes 280 and above insulated bearing housing isprovided as standards. Good installation practicecan reduce the risk of bearing current. Somerecommendations are as follows.● Effective grounding of drive system components

(Drive, Motor, Driven equipment) Ensure goodHF bonding for potential equalization betweendrive components.

● Use of symmetrical motor cables with armourshield

● Proper installation of motor cables and connectors.

Electromagnetic CompatibiltyBy following inverter manufacturer’s recommendationon earthing, screening, filters and cable layout,emission requirements of EN50081 and immunitylevel of EN50082 Part1 for domestic and part2 forindustrial environments can be achieved.

Motor ProtectionVD series S1 duty motors in frame sizes 200 andabove are recommended with thermistor protectionas standard. 3 Nos. PTC140 (Class B Rise) providedin winding overhang are connected in series andthermistor terminals are brought out to terminal box.For operation with Class F rise PTC160 thermistormay be provided.

AccessoriesEncoders/tachogenerators are required to provideclose loop control between inverter and motor foraccurate position control and monitoring. These unitsare fitted at NDE side on request.Incremental encoders provide feedback on rotormovement by converting rotational movement intoelectrical signals used for numerical processing forprecise speed control. Incremental encoders operatingon photo electric measuring principle provides veryhigh degree of measurement accuracy. AC Tacho-generators using permanent magnet rotor are usedfor simple speed monitoring and control. They convertthe input speed to a three phase voltage whosemagnitude and frequency is proportional to speed.

Drive SelectionDrive rating should be selected based on RatedCurrent of motor. For loads requiring higheracceleration torque a larger drive may be necessarysince standard drives provide 150% FLT duringacceleration. It should also be noted that motorperformance is dependent on drive parameters eg.Modulation process, carrier frequency, voltage risetime, cable length etc. Accordingly drive parametersas specified in motor selection table should beconsidered during motor selection.Motor SelectionSelection of motor rating should be based on following–● Check the type of load and speed range –

Constant Torque, Constant Power or Variabletorque. For Constant torque application calculateTorque requirement throughout the speed range.Refer to ‘Motor selection chart (4 pole and 6Pole)’ for selecting recommended motor framesize with Class B temp. rise. For sustainedoperation at lower frequencies (<10 Hz.) underconstant torque condition and for sustainedoperation beyond base speed (Constant Poweroperation), force ventilated motor is recommended.For constant torque operation below 5 Hz., referto MARATHON Electric for voltage boost details.

● Check and consider ambient temp., altitude,Supply voltage, Frequency and variation to checkmotor rating. Apply Re-rating factor as required.

● Calculate acceleration time based on 150% motortorque superimposed on load characteristics andcheck whether this is acceptable. This is particularlyimportant for high inertia drives. (Most drives arerated for a short time current of 150% ratedcurrent for 60Sec.)

● Check and ensure that maximum permissiblemotor speed (Table -5) is not exceeded.

● For constant power operation beyond 80Hz. Referto MARATHON Electric.

Data Required for Motor SelectionFollowing details are required for selecting motorrating/Frame Size for Variable speed drives.● Supply Voltage● Base speed at Mains Frequency● Motor Polarity Speed Range● Type of Load – Variable Torque, Constant Torque,

Constant Power● Load characteristics and load GD2 – Calculate

Required accelerating torque.● Duty details● Motor Enclosure

• POLICY : Every Care has been taken to ensure the accuracy of the information contained in this publication, but due to a policy of continuous development and improvement the right is reserved to supply productswhich may differ slightly from those illustrated & described in this publication.

A Regal Brand

www.regalbeloit.com

Paharpur Works58, Taratala RoadKolkata - 700024Ph: 91 33 4403 0400Fax: 91 33 2469 5369/8530

www.marathonelectric.com

Motors

AEI Works1, Taratala RoadKolkata - 700024Ph: 91 33 4403 0500Fax: 91 33 2469 6988

TM

MEMI/CAT/VD/0112/03 Replaces MEMI/CAT/VD/0111/03