Hello everyone in this good and informative forum

Well, I'm repairing ups machines almost everyday, with different capacities... Starting from 1kva and upto 160kva
Single phase and 3 phase

We all know this bulb current limit circuit.. Right?
I use this for single phase machines.. For ac current limit.. And it's useful for me, when test the ups online mode.

For dc current limit I use this high watt resistor...
And it work for me... When try the test after repair on battery mode... To limit the DC current..

If any over current, this resistor heat up.. And abnormal behavior for UPS appear, so I know there is still something wrong...

In 3 phase machines, is there any posibble way for current limit?

For 3 phase machines battery mode... Can start at +/-192v ". 16 vlra batteries 12v each" , or 20 battaries.. +240v,or more.. etc

I just need safe test after repair
Any ideas?

I'm talking a bout the online UPS type

 

For 3 phase machines, use one incandescent light bulb per phase.
EDIT: ALL should be same wattage bulbs.

 

YOU CERTAINLY CAN use series light bulbs as safety limiters when testing battery powered devices. But it is a bit more complex than with AC mains powered devices.
Three series lights for 3-phase machines makes sense to me!

 

Certainly, 3-phase power in becomes a bit more complex, especially if phase-balancing is a consideration. Monitoring phase balance adds a fairly big bit of complexity to your test implementation.
If there is no chance of any gross overcurrent, then a matched set of series resistors, along with three isolation amplifiers, would be one choice.

 

For 3 phase machines, use one incandescent light bulb per phase.
EDIT: ALL should be same wattage bulbs.

Ab you show photo for lamp?

 

What is not mentioned in detail is HOW MUCH CURRENT?? That matters quite a bit. Certainly incandescent light bulbs work well within limits, and they are fast enough to limit shorted circuits as well, mostly. The challenge is that if the limiting is also required to prevent excess current damage to the load, it must be sized corrctly. That makes the selection more complex. also, loads drawing more than an amp or two may not work with the series light bulb scheme , because when the bulb lights it is in a higher resisance mode and already limiting the current.