14
EN Drive Installation Manual
Transformer Sizing
If your application requires a transformer, use the following table for sizing the KVA rating.
The values in the table are based on “worst case” power usage and can be considered a
conservative recommendation. Worst case power usage assumes a motor and drive are
running at the max. continuous operating point continuously (Max Torque, Max Speed). You
can down-size the values only if the maximum power usage is less than the transformer
continuous power rating. Other factors that may influence the required KVA rating are high
transformer ambient temperatures (>40° C or >104° F) and drive operation near the maximum
speeds.
To calculate the power usage of an application use the following formula:
Selecting a proper transformer for the application depends on the type of motion the
application requires. For applications with continuous velocity motion, multiply the
Continuous Power by 1.5 and select the closest transformer size greater than or equal to this
result. For applications that require positioning (multiple starts and stops) use a multiplier of
2 to determine the transformer size.
It is always better to oversize the transformer. Transformer life is directly dependent on the
temperature of the windings and if the transformer is undersized the life of the transformer
can be decreased. Undersizing may also lead to a voltage drop of the secondary under heavy
load conditions.
Drive/Motor Combination
Suggested KVA Rating
EN-204/NT-207
0.44
EN-204/NT-212
0.77
EN-204/MG-205
0.22
EN-204/MG-208
0.44
EN-204/MG-316
0.76
EN-208/NT-320
0.76
EN-208/NT-330
1.28
EN-208/NT-345
1.67
EN-208/NT-355
1.99
EN-208/MG-316
0.76
EN-208/MG-340
1.49
EN-208/MG-455
1.85
EN-214/NT-345
1.67
EN-214/NT-355
1.99
EN-214/MG-455
1.85
EN-214/MG-490
2.84
EN-214/MG-4120
4.26
RMS Torque (lb-in)
Avg Velocity (RPM)
1.1830
5
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Continuous Power (KW)
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