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Latch Solenoid Used As a Filter Inductor

IP.com Disclosure Number: IPCOM000035168D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Ramage, JG: AUTHOR

Abstract

Described is a method of employing the solenoid of an electromagnetic latch to serve a dual purpose as a filter inductance. Savings of component cost, space and power dissipation result.

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Latch Solenoid Used As a Filter Inductor

Described is a method of employing the solenoid of an electromagnetic latch to serve a dual purpose as a filter inductance. Savings of component cost, space and power dissipation result.

Removable equipment using electric motors driving high-speed rotating parts that constitute a safety hazard to the operator are required to employ electromagnetic locking latches to prevent access into the housing or removal from a rack while the motor is rotating. Such equipment may also require a filter inductor in series with one of its DC supplies and the motor drive electronics to prevent interference to other sensitive circuits on the same DC supply by rapidly switching high currents in the motor driver. The nature of the motor current through the filter inductor and the requirements of the latch solenoid winding are such that the inductor function can be provided by the solenoid.

The example chosen is a 12 V motor, speed controlled by chopped DC pulses. Fig. 1 shows the solenoid winding incorporated as the inductor in the pi- filter network between the +12 V DC supply and the motor drive electronics. Fig. 2 shows how the average current demanded by the motor changes from when it starts to when it has reached the normal running condition. The variation in absolute current levels given are what may be experienced over a large number of units. During starting, the current is DC but during running it is pulse-width modulated, as shown in Fig. 3, to give the lower average current. The chopping frequency would be typically a few tens of kHz.

One of the major constraints on the solenoid winding is its resistance. This must be of the order o...