Power Supply Question

[quamit]

I posted this under Geckos but may have picked the wrong group.
I have been working on a 4 axis controller using 201's with a campbell combo board. My supply is 30vdc with 2 capacitors and fed to the 201's from a fuse block.
1. When I setup my first power up test for one drive I was surprised at how long it took the red light to go off on the drive indicating the caps had lost their bite. Do I need to worry about creating an arc if I unplug a motor while this light is on?
2. I have a 3 prong plug on my AC side of the transformer which also powers the Campbell board. The green ground is attached to the case chassi. Should the neg side of the capacitor for the DC side be attached as well or does this negate isolation on the 30 VDC curcuit?
Thanks in advance.
Regards
Tim

[ger21]

If you unplug a motor while the drive is powered, you'll destroy the drive.

[NC Cams]

Try putting a 3.3K ohm discharge/loading resistor across the caps.

While under power, the resistors will only dissipate 9 milliamps which is only about 0.27 watts. A 1 watt or larger resistor should not get hot during discharge or even under 100% duty cycle.

This will dissipate the voltage in the caps far faster than an LED or some other low power indicator. BTW, this is the same size cap used on my 100v Bridgeport servo power supply cap.

[Eurisko]

Hi Tim,

In answer to your second question,

Don't connect the green AC ground to the capacitor. This will negate the isolation provided by the transformer.

Just make sure that both the AC and DC sides are equipped with properly rated fuses.