In mPRO-200 the protection feature is based on mathematical model of motor thermal image. The motor thermal overload protection function calculates the heat accumulated in the rotor and stator based on the effective heating current , integrated over a time. The relay appropriately takes in to account cooling of the winding by gradually emptying the accumulated current bucket. The relay displays the status of thermal condition of motor windings as a % of maximum permissible Thermal capacity. If inverse overload characteristic (lN\/) is selected then only the effect of thermal memory phenomenon is enabled. If current in any of the three phases exceeds over-current setting l> as well as accumulated thermal capacity (Thermal MEM) is >=100% then mPRO will trip the motor. If thermal memory is accumulated then Relay Contact Reset depends on Relay Reset selection (AUTO/MANUAL) and Thermal Reset selection (Disable/Enable).
Mechanical equipments such as pumps orfans can be quickly damaged if it jams, resulting in a locked rotor stall. The MPro will trip when the running current exceeds the set value (Stall) value after the Stalled Rotor Time (tStall). Set this value to ‘OFF’, if stall protection of driven equipment is not required since the thermal overload protection will protect the motor. This feature is blocked during the inrush of motor starting.mPRO provides protection against over temperature by monitoring the temperature in the motor winding. High winding temperature is caused by phase unbalance, phase fail, high torque starting, insufficient cooling etc. mPRO will trip the motor in running condition after PTC trip time (tPtc) expires. once temperature monitored via external PTC thermistor exceeds the PTC Trip value (PtcTrp).
