Power Supply Question

[jjwl89]

If I was using 3 servo motors that at stall draw 44 amps each with Gecko 320's which allow a maximum current of 20 amps with fuses to prevent to much power to the motors, would I need a power supply capable of providing 60 amps? Where can I get transformers that could provide 60 amps? Also, how is that VA rating for transformers calculated?

[ynneb]

What is the continuous running rating of your servos? Amps?

VA means Volts X Amps. So if a tranny has 10 Volts and can deliver a constant 10 amps, it means it has a 100VA rating.

If you are looking for a transformer with high amps, you are probably better off getting one made up for you. Just shop around with the quotes before hand though.

[jjwl89]

They have a nominal voltage rating of 60V and a maximum continuous current rating of 8.9A.

[sendkeys]

[ynneb]

Then I guess you will need a transformer that has about 42 Volts AC output and 30 Amps rating. Once you rectify the 42Volts AC it will become 60 volts DC.

The transformer will be 42V x 30A=1260 VA

This will be suitable for you setup I think. If you are in any doubt you can always beef up the amperage just to make sure. Dont however beef up the voltage because this will damage your servos.

[arvidb]

A 42 VAC, 30 A transformer would give you about 58 VDC, 21 A continous output. If you want 30 A out, you need to use a transformer rated for 42 A.

UDC = UAC * sqrt(2)
IDC = IAC / sqrt(2)

You cannot get 58 VDC * 30 A = 1740 W DC out with only 42 VAC * 30 A = 1260 VA input.

Arvid