Motors space heaters

Motor space heaters above 30 kW control bus voltage generally... 

It is recommended that the motor should have separate terminal boxes for the main supply and for the accessories such as space heaters, embedded teinpertiture detectors, bearing temperature indicators and moisture detector terminals, etc. In LT motors, however, if it is not possible to provide a separate terminal box for these accessories, the main terminal box may be adequately spaced to segregate the.se terminals from the main terminals within the box. 

Space heaters motors above 30 kW must be provided with anti-condensation space heaters suitable for 240 V 50 Hz (or 60 Hz), a.c. supply. The space heaters must switch ON automatically when the motor is out of. service. Motors of 30 kW and below must be suitable for connection to a 240 V. 50 Hz (or 60 Hz) a.c. supply. Here also the windings must be connected automatically to the 240 V supply when the motor is out of service. 

In HT motors the terminal box for space heaters and embedded temperature detectors must be separate from the main terminal box. 

In certain cases, where the motor is too large and it is idle for a long period before it is installed and electrically connected (the space heaters are therefore OFF) even these heaters may not be sufficient to absorb moisture which might have condensed deep in the slots, unless, of course, the heaters are kept ON for a considerably long period. In such cases, it is advisable to heat the motor by methods 1 and 2 in addition to using the built-in heaters, until the insulation level of the windings reaches the required level. Once the motor has been installed, these space heaters, when provided in the windings, are switched ON automatically as soon as the motor is idle, and thus eliminate deep moisture condensation. 

A motor used in standby operation mode should be equipped with a space heater to keep the motor windings dry. In classified areas these space heaters must meet the surface temperature requirement of the specific hazardous area. 

Space heaters, particularly in electrical motors and generators which may be idle for significant periods of time, can also help prevent the accumulation of moisture. Space heaters installed in classified areas must operate at temperatures below high temperature devices. 

I. Space Heaters. A resistive heating device installed in the motor to prevent condensation when the motor is not operating. This requires a special control system. 

The motor shaft is usually held in place by two insulated slide bearings equipped with ring lubrication. In addition, the bearings are cooled for example by an oil-water cooling system. The terminal box of the motor should be so dimensioned as to accommodate the current transformers for differential protection of the motor. To prevent the formation of condensation in the motor during standstill, a space heater is installed. 

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