Electrical Power & Protection


LV and MV motor protection

January 2012 Electrical Power & Protection

NewElec’s 320 to 327 M series of relays provides protection for LV and MV motors in industrial as well as mining applications, especially where they are working at or close to full RMS loads.

The relay is particularly useful when starting high inertia loads that take a while to accelerate to speed as it is fitted with a start timer that effectively moves the thermal overload tripping curve away from the effects of the inrush current for the duration of the acceleration time. On completion of the required start time the curve immediately returns to its ‘motor running’ position. The thermal utilisation by the motor while accelerating is nonetheless captured by the protection relay.

The relay incorporates a 4 to 20 mA output loop for monitoring the motor load as well as an optional display meter depicting the thermal state of the protected motor. The user only requires five pieces of information to protect the motor properly and adequately. These are: maximum load of the motor; manufacturer’s permissible starts per hour; consecutive starts; on site measured application starting time; and safe hot stall time of the machine. Armed with this information the user can set up the relay accurately.

Additional features include programmed limitation to start attempts, alarm outputs for overloading and unbalance, earth fault and short circuit protection with back-tripping facility into MCCB, as well as user-friendly LED fault diagnostic displays.

For more information contact Luc Dutrieux, NewElec, +27 (0)12 327 1729, [email protected], www.newelec.co.za



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