Rishabh Instruments Limited | Rish Relay 252-PMx

Rish Relay 252-PMx - Thermistor trip Relay

The protector operates by de-energizing a relay when the thermistors fitted into a motor stator detect a temperature condition. An illuminated green LED indicates critical when the temperature is within normal working limits.

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LED trip indication
2 pole relay contacts
Energize/De-energize function swapping
Auto / Manual Reset

Principle of operation

The protector comprises a voltage level detector which detects the voltage across the thermistor. At normal temperatures, when the thermistor resistance is low, a command signal energizes a change-over relay, and a green LED shows a safe condition.

At a predetermined temperature, the thermistor resistance increases rapidly, which de-energizes the relay. The actual trip temperature is governed by the thermistor characteristic, which can be obtained from the manufacturer’s data.

Failure of the supply to the unit or open circuit in the thermistor winding will cause the relay to de-energize, thereby providing a failsafe facility.

Applications

The thermistor Trip Relay, when used in conjunction with positive temperature co-efficient thermistors, will help protect against

Sustained overload
Single phasing
Locked rotor
Blocked ventilation
High ambient temperature

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