Well, I had been hoping to post that my Servo Dynamics SD-3030 spindle drive was fixed, but it's not quite yet. I repaired a bunch of burned out wiring in the power supply. It turns out that the OEM put wire ties every 1/2 inch on all the wires. Great, but over what I guess are power resistors, the ties were so tight that when the wire insulation got brittle due to the heat, the ties just wore through.
The net effect of this was that the fan stopped working, causing further wiring failure. I replaced everything with automotive grade wiring, which solved some of the spindle problems (e.g. now the spindle turns on initialization). However, I was still having an error during initialization. The spindle would spin up, then the drive would error out with an over-voltage error. Careful examination of the 6 rectifier diodes revealed one with clear burn marks. It was replaced.
I thought this would be the end of it, but the drive still errors out at initialization with the same behavior (spins up for 10 seconds, then errors with overvoltage). Resetting the drive produces a large buzzing sound from what appears to be the power supply. I suspect that more of the rectifier diodes are bad, but am not sure. The DC drive voltage reads 80v and I haven't had time to check the bus voltage coming from the power supply yet.
The manual stats that the error led is as follows:
Code:
Voltage - This LED will give an indication for these conditions:
1) Bus voltage has exceeded 195 VDC, this condition can exist if:
a) The shunt regulator fuses are blown
b) A regulator is required to handle regenerative motor
energy, while decelerating, due to excessively high
inertia.
2) The sum of the +/- 15 Volt Bias supply is less than 28 Volts
DC. This condition can exist if a line transient causes
the bias supply to dip momentarily or the bias supply has
failed. Check bias supply fuse.
I checked the shut regulator fuses, and they are OK, and there is a regulator. Also, since the noise on reset exists at dead stop, it would seem that the problem is elsewhere.... I also checked the bias supply fuse and the voltage sum. Both seem OK.
The power supply seems pretty simple. It's basically six rectifier diodes that rectify the incoming 3-phase AC into DC, then pass it to a large filter capacitor. There is also circuitry for shunt regulator which feeds three large resistors. I don't know enough about power drives to understand the whole thing, but it seems that the only two places that could generate overvoltage would be either the cap or the rectifier diodes. I suppose the switching MOSFETs on the shunt regulator could also be bad, but this would not explain the buzzing on reset.... Or it could be wired to the wrong ends on the transformer (hmmm, should check that first...). My next step is to test the power supply more thoroughly, starting with the rest of the diodes and the capacitor.
The other possibility is the power output stage of the amp, which is a bunch of MOSFETs driven in PWM fashion at 2Khz. One interesting thing was that when I disconnected the control and tach inputs, then started the machine, the drive went into run-away mode, something I did not expect. I thought that enable and signal were necessary at least for the thing to run. This may or may not indicate a problem with the amp itself. I'm going to take the heatsink off the MOSFETs to see if I can divine anything from their looks...
Regardless, I've been trolling ebay and the 'net to find a reasonably cheap replacement. If anyone knows of a 150-180v 6HP (~30-40A) DC motor controller with integrated power supply for a reasonable price, please tell me. I do have an AMC controller of the right size coming, but no power supply... In the meantime, I'm continuing to troubleshoot the amp as best I can. I have an o-scope and various other electronics testing tools, as well as the manual for the amp, but I don't know an enormous amount about these things, so it's slow going.
In other news, I designed and had made some breakout boards to convert the existing control system to Mach3. They arrived today. I now have most everything I need for a conversion, so I'm going to start on that next week.
If anyone has ever worked on a Servo Dynamics drive and has some pointers, I'd be grateful if you'd be willing to share your wisdom.
Thx.
Chris.
Reply with QuoteOriginally Posted by befega
