12/29/2022 0 Comments Ontime feeders partsIf a shading ring should be omitted when reassembling some types of contactor after maintenance, the omission will be obvious as the magnet will ‘hum’ loudly when energised. They fulfil the basic function of providing a secondary magnetic flux to prevent the magnetic pole faces parting and reclosing when the flux produced by the operating coil passes through zero. magnets are fitted with shading rings which normally consist of a single short-circuited loop of copper alloy. Operation – In order to provide quiet operation, a.c. The coil must be constantly energised in order to keep the contactor closed.Īlternatively, contactors can be fitted with a mechanical latch which does not require continuous energisation. If the voltage to the coil fails or falls below a defined level, the contactor opens, thus disconnecting the motor from the supply. The contactor is magnetically held closed by maintaining the current flow through the coil. Schneider Electric’s contactor 1NC 18A 400V AC3 220V/50Hz offer proven performance for resistive loads or large motor starting applications such as fans, crushers, pumps, compressors and overhead cranes. In most cases the material used should have a relatively high melting point and mild steel can be used. The cooling plates or de-ion plates do not need to be selected for their electrical conducting properties. These may take the form of cooling plates or shrouds which simply enclose the contacts, or an array of de-ion plates similar to those in a circuit breaker. Larger sizes of contactor usually require the use of cooling devices inside the arc chamber to assist with arc extinction. supply and the ‘stretching’ of the arc by the opening of the contacts gives adequate performance. contactors of up to 22kW rating do not require complex arc chamber design – the combination of the natural current zeros of the a.c. The method of arc control is also critical in determining the performance of the contactor.
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