On Tue, Mar 29, 2022 at 07:22 AM, Jean-Paul wrote:
Bonjour at these power level best practices woul us a switching supply not
linear
We use large Variacs to reduce Inrush.
The thought of sudden application of DC bus to vintage mil equipment is bad.
The mil-surplus equipment I'm interested in powering has dynamotors. As you know a DC motor is nearly a short circuit when stationary, and very few if any dynamotors had a soft-start circuit. They are designed to have the DC "suddenly" connected with a big switch, after all... If you're concerned about electrolytics reforming I would have done that already with external power supplies before just throwing the switch :) same for the dynamotor bearings, I always remove and relube them.
The big problem with switching supplies is that they cannot handle momentary overloads without shutdown, thus unsuitable for motor-start applications. And the inrush current on a dynamotor is usually 3-4 times the full load rating. That holds true for the large rotary inverter I'm powering (FL = 115 amps, inrush = 420 amps).
Also the switchers are not inexpensive at this size. The weight (50+ lbs) of this linear supply is not a problem, and it's not that much physically larger than a 3000 watt switcher, or stacked smaller ones. In fact, to handle the starting surge of this inverter, I would need switchers capable of supplying the full 420 amps which would be VERY costly. Or rig a pair of floating 12 volt batteries, which are also expensive, bulky and heavy.
Sometimes simple brute force works the best :)
