TEFC Motor in Class I, Div II Area

[mkmorris]

I saw this forum. (https://forums.mikeholt.com/threads/class-1-division-2-group-b.13157/)

I am looking to install a motor and gearbox in a Class I, Div II, Group C&D environment, and trying to avoid something custom. I saw that TEFC motors could be used. I would like to run the motors off a VFD from 25hz to 90Hz, assuming it is inverter duty rated (Baldor Reliance IDM3774T). Drive is run off of pump demand. Is TEFC still allowed or is a custom motor required for the application?

Any feedback you may provide is greatly appreciated.

- Mike

 

[don_resqcapt19]

The following is from NEMA's MG-1 document.

14.32 Operation of Alternating-Current Motors from Variable Frequency or Variable Voltage
Power Supplies, or Both

14.32.1 Performance

Alternating-current motors to be operated from solid-state or other types of variable frequency or 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 that
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.