14.32 OPERATION OF ALTERNATING CURRENT MOTORS FROM VARIABLE-FREQUENCY OR VARIABLE-VOLTAGE POWER SUPPLIES, OR BOTH
14.32.1 Performance
variable-voltage power supplies, or both, for adjustable-speed-drive applications may require individual consideration to provide satisfactory performance. Especially for operation below rated speed, it may be necessary to reduce the motor torque load below the rated full-load torque to avoid overheating the motors. The motor manufacturer should be consulted before selecting a motor for such applications (see Parts 30 and 31).
WARNING: Motors operated from variable frequency or variable voltage power supplies, or both, should not be used in any Division 1 hazardous (classified) locations unless :
a. The motor is identified on the nameplate as acceptable for variable speed operation when used in Division 1 hazardous (classified) locations.
b. The actual operating speed range is not outside of the permissible operating speed range marked on the motor nameplate.
c. The actual power supply is consistent with the type of power supply identified in information which is supplied by the motor manufacturer.
For motors to be used in any Division 2 hazardous (classified) locations, the motor manufacturer should be consulted.
High frequency harmonics of inverters can cause an increase in the level of leakage current in the motor. Therefore, users are cautioned to follow established grounding practices for the motor frame.
Failure to comply with this warning could result in an unsafe installation that could cause damage to property, serious injury or death to personnel, or both.