DC speed control as power supply for g320?

[DennisCNC]

Is there a reason why this type of speed control will not work as a power supply for the g320 drive:?
http://images.google.com/imgres?imgu...icial%26sa%3DN

[Mike Nash]

Yes, there is a reason it won't work. The G320 needs a power supply with a filter capacitor because it is a Pulse Width Modulation type controller running at a fairly high switching frequency as compared to the SCR type controller you linked. You might get away with adding an external capacitor, but then again, you might not. These KB drives work well into resistive and/or inductive loads, but aren't designed for driving capacitive loads. If the regulator gets unstable it could fail due to high current draw charging the capacitor initially if it does not ramp the voltage slowly enough. It could also damage the G320 if the voltage overshoots above the 80V rating of the G320.

[DennisCNC]

I tried it anyway, with the motor on the bench with no load seems to work good keeps the voltage steady with a capacitor. In a few days I will try it with some load and report back what I find.

[DennisCNC]

Got the motor connected to the gear box, this is on a rack pinion system. It comes out to 770 step/inch at 1300 IPM max and 100 u/sec accel. The powers supply/dc speed controller at 72 volts. The motor is a regular 90vdc with a twisted armature and 100 line encoder. With me sitting on the entire setup (190lb) it has no problem going full speed and after 5 minutes the speed controller didn't even rise in temp. the g320 barely when above room temp. with no heat sink. I say the setup is a winner.

[Mariss Freimanis]

Please don't do that!!! Two reasons:

1) An SCR speed control, light-dimmer, etc. is a phase-triggered device. Once turned on, an SCR cannot be turned off until the voltage drops to zero across it. This happens 120 times a second with an AC voltage. Should the SCR trigger early in an AC cycle, the output voltage will rise to 162V for that cycle and destroy the drive.

2) An SCR control has no AC isolation. Trace the circuit from its output backwards and you will have a connection to your 115VAC receptacle. You touch the drive and you may as well be sticking your finger in a light socket. In other words, you can kill yourself.

I don't mean to be a stinker about it but we feel so adamantly against this idea that doing so voids the warranty on the drive. It is dangerous and destructive.

Mariss

[DennisCNC]

I see.