Answer 6—Adding a parallel R-C network in series with the solenoid can reduce holding current. For example, if the coil resistance is 60 W and the holding current is to be half of the full current, a 60-W resistor is required. Then, if the pull-in time constant needs to be on the order of 10 ms, a 330-µF capacitor (10 ms/30 W) or more is required.

By cutting the holding current in half, the release time is also improved by a factor of two on top of any other techniques being used to improve that aspect of circuit operation.

Contributor: David Tweed