[MRCA] Dyno Starts Trip Breaker on PP-7333

[Christopher Bowne]

I finally got a chance to put the 60A 28VDC PP-7333 power supply I picked up at Gilbert on service with my ART-13 and GRC-19.  I am floating my pair of series connected 12V deep cycle batteries across the output of the power supply to take up the starting surge of the dynos.  The setup works fine steady state, with the PP-7333 carrying the load with no strain, but the unit's DC output breaker keeps tripping on dyno startups, such as keying the mic on the ART-13 in voice, even though the batteries have a full charge.  For now, I am using a work around of starting the dynos directly off the batteries with the DC output breaker on the power supply open then shutting it to take the steady state load.

I am thinking that the trips are being caused by the output voltage on the PP being slightly on the high side relative to the batteries, which I suppose could also cause them to overcharge at some point.  Since the PP voltage is on the high side, there is a lot of current draw from it, and pop goes the breaker!

The previous supply I was using was designed to float a pair of batteries and the paralleled load.  I would set the output voltage so that it was very close to the battery voltage, hence little current draw at "idle" and most of the starting surge came out of the batteries.  I never had a DC supply breaker trip problem on dyno startup with that set up.

I do not yet have a manual for the PP-7333, just a schematic from the inside of the unit.  Is there a way to slightly lower the output voltage to about 27.6 V (2X13.8) which is about what the fully charged batteries voltage would be?  Right now, I think I'm getting, accordng to the PP's voltmeter, about 30V out. There is no ammeter on the PP7333.  

If the PP output is not adjustable, maybe a high current dropping diode or two in series with the output?

73. Chris, AJ1G
      Stonington, CT