KB355: PM42 Short Circuit/Auto-Reversing Failure when used with DCS50 (Zephyr)

PM42 Short Circuit/Auto-Reversing Failure When used with Zephyr (DCS50)

The PM42 is designed to control 4 independent power subdistricts that can be set up as either a “Short Circuit Manager” (the factory setting) or as an “Auto-Reversing Controller.” The PM42 factory setting for trip current is 3 amps. The trip current can be modified to settings from 1.5 amps – 12 amps to accommodate the needs of your system. In addition, each of the 4 power subdistricts can be set for slow, regular, faster or fastest short circuit management.

While a trip current of 3 amps will work with most boosters, the Zephyr is only a 2.5 amp unit, so the PM42 must be reconfigured to trip at 1.5 amps. Otherwise, the booster will trip before the PM42, shutting down all the sections of track controlled by it not just the one section controlled by the PM42 that has been affected. It is also advisable to set the trip speed for all four sections to “fastest.”

To change the trip current and sensitivity (trip speed) you must change Option Switch settings on the PM42. See your manual for the details on changing OpSw settings. The factory setting for all Option Switches is t (thrown). The following changes should be made to work with the Zephyr.

1.  Set Trip Current to 1.5 amps: Change OpSw 09=c

2.  Set the Short Circuit Sensitivity to “fastest” for each section.

Change OpSw03, OpSw11, OpSw19 and OpSw27 all to c (closed).