Protection for wound rotor motors

November 13th, 2013, Published in Articles: Energize

Wound rotor motors are typically used in applications requiring high starting torques, a limited number of operating speeds, or a stepped acceleration to achieve a soft start. Designed to protect wound rotor motors used on winches or overhead cranes, NewElec’s 330 Series low voltage electronic motor protection relay, when placed in the crane operator’s cabin, will provide him with a visual display of the operational state of his crane motor in terms of workload. He will now be able to see whether or not he can work the crane harder or whether he needs to reduce speed. The motor duty class, starting class, cyclic duration factor, power and load current value are of fundamental importance and permit accurate full load protection and adjustment. The inverse thermal curve caters for a cyclic duration factor that offers both stator and rotor protection. This allows the motor to be used to its full duty class and CDF, but still maintain accurate, repeatable protection on small or marginal loads. Maximum load threshold is adjustable between 30% and 100% of the C.T. primary current.

Contact Luc Dutrieux, NewElec, Tel 012 327-1729,

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