# How to size a power supply for x-y stage?

1. Aug 2, 2013

### El Moriana

I have a couple of linear motors + their drivers and I'm trying to make an X-Y stage for a prototype milling machine, but I'm still a student and in a mecheng stream and haven't sized a power supply before, so not sure how to do it. So far this is my thought process:

Motor specs: 340VDC (max bus voltage), 4.5A continuous current
Driver specs: 24-80VDC, 1A max

Two of each.

Method 1
I simply do a P=Ʃn.IV calculation (n is quantity) and then size it using total watts and spec it through max voltage and max current? This method seems like overkill..

Method 2
Use the force I need this thing to exert to get needed power, then pick values of voltage and current that give this power and that are lower than the maxes. Use these P, V and I values to spec the supply?
(if this one is correct, how do you decide on what the voltage and the current are?)

2. Aug 5, 2013

### Baluncore

Calculation is based on maximum currents and voltages, not mechanical work that will be done.
Mechanical work was taken into account when specifying the motors.

The particular practical solution will depend on the details of the AC supplies available and the isolation requirements of the DC rails needed.

If you have 3 phase 400VAC you can probably just rectify that with three diodes and storage capacitance to produce a 325VDC rail. Regulation is probably not needed for the motor supply. The rectified DC appears relative to the neutral of the 3 phase supply. 4.5A x 2 = 9A continuous. 30A diodes rated at 800V are cheap.

If 24VDC is sufficient for the controller then any 24VDC switch-mode power supply capable of delivering 2 Amps will satisfy the controllers. DIN rail mounting supplies are available with either 24VDC or 48VDC outputs. They will meet your requirements.

3. Aug 6, 2013

### meBigGuy

You need to account for the startup current and stall current if you want the system to be safe.

4. Aug 6, 2013

### Baluncore

The motor controllers should be using something like an H-bridge to efficiently drive the inductive DC motors. The controller should limit the motor current to protect it's H-bridge switches and the motor. Most controllers will have a programmable or physically adjustable current limit.

The controller current limiting effectively protects the power supply, the H-bridge and the motor.