请教 关于电机的空间加热器

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7.3 MOTOR SPACE HEATERS
7.3.1 For increased reliability, a motor can be equipped
with space heaters or a low-voltage (usually 24 to 32 volts
AC) circuit to keep the motor windings dry while not in operation.
For motors located in classified locations, space heaters
should operate with surface temperatures not exceeding
requirements of the NEC for the flammable gas or vapor that
could be present. It is recommended that motors 50 hp and
larger be provided with space heaters or other anticondensation
system.