question if i connect 3 power supplies together (1@ 20A 2@ 5.85A) in parallel

if i connect 3 power supplies together (1@ 20A 2@ 5.85A) in parallel would that give me 31.7A output?

yes same voltage

Don’t do that. It does not work well like this. Same voltage is not the same under load.

It is not something I would recommend. If you need 30A, get a supply for that, otherwise, maybe your load can be split into two or three loads so each one goes to one supply.

This can be done for example for 3D printers with RAMPS boards, that have two power inputs for 11A and 5A. These inputs may come from the same supply or from two different sources.

I would be leery. I have seen people ask about ganging up voltage regulators to get more current. It had usually been discouraged. IIRC it has to do with making the regulators work to cover for the ones that are slacking.

thanks thats all i needed to know i was going to separate them anyway just asking the question

If you keep one supply for one motor, and the motor is <=5A, you’ll be ok. The 20A one you can use it for a few motors.

Yes and no, Gary. Potentially, you could run a high amperage device this way, but the danger is not worth the risk. The likelihood is that the weakest device would fail obviously and either short the others or would fail silently and overdraw current from the remaining, causing a cascade failure. Both are likely to cause overheating and a fire. IMHO, spend the money and save your home or workshop as well as your life.

thanks my motors are only rated at 3.5A so i dont even need to consider it it was just something i needed to get straight in my head

Then the 20A one is more than good enough!

when it says the motor is rated at 3.5A is that at the holding torque? and therefore less when they are actually working?

If you are talking about a stepper, yes. A stepper motor not rotating is drawing locked rotor current and if the power supply or controller does not limit the current, the motor will burn that winding. If you are talking about a regular AC/DC or synchronous AC motor, no. For these, the nameplate is usually marked RLA for Run Load Amperage and this is the maximum run current at full load and these motors draw tens to hundreds of times the RLA if they stall and the windings will smoke in seconds.

steppers thanks Bear U

@Alex_Lee yes it did occur to me even though i will have rcb’s you cant have too much protection

No Problem… hate to see you stall a spindle and roast it! :wink:

You are right. Unless you have a drive with a current hold reduction circuit in it. Then you’re still right, but with a caveat. Modern sophisticated stepper motor drives use various techniques to get around the basic physics of inductive reluctance. Although none get around it completely.

Setup properly a stepper drive should not be able to burn out a stepper motor. Of course if the drive is setup improperly then the danger exists. Modern stepper drives are current limiting power supplies though, with sequencers. Even the old drives had current limiting capabilities. Or you just ran a motor at its rated voltage.