KBPC-240D DC Motor Controller has no output

Thread Starter

ScottMR

Joined Apr 4, 2024
19
My son bought this controller to run a 90VDC motor. It doesn't work, so he gave it to me to fix. So far, I have checked all the jumper settings, pot settings and condition of fuses and switches. I wired the AC plug to it. I cleaned up the wiring to the motor. I plugged it in and I'm not seeing any DC power to the motor at all. I suspect something is wrong with the bridge rectifier. I've tried to find a schematic for this board online, but so far have come up empty. Just as useful would be a repair manual. Does anyone out there have experience using and troubleshooting this controller?
 

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MisterBill2

Joined Jan 23, 2018
18,958
To verify the rectifiers you should be able to measure a DC voltage across a large filter capacitor.
Looking at the boards I see one jumper set for torque instead of speed.
Where did your son buy this motor driver? Did you verify that the motor is not short circuited? And, is one of those blue terminal strips an "enable" input? Also, check that the speed control actually applies a voltage to the speed control input.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
To verify the rectifiers you should be able to measure a DC voltage across a large filter capacitor.
Looking at the boards I see one jumper set for torque instead of speed.
Where did your son buy this motor driver? Did you verify that the motor is not short circuited? And, is one of those blue terminal strips an "enable" input? Also, check that the speed control actually applies a voltage to the speed control input.
Hi MisterBill2,
Thank you for your input. Let me address each comment.
1. This design does not have a large filter capacitor, like you would see in a linear power supply. There is only one small electrolytic cap on board.
2. There is a jumper for torque vs speed mode. I tried each setting and either one didn't magically make the thing work. For the farm, the 90VDC motor will be part of a hops picker and torque is more important than speed.
3. My son bought this controller used from someone who told him that it worked.
4. Yes, I verified that the motor is working. I applied a DC voltage to it and it runs fine.
5. One terminal strip is a relay output to monitor if the unit is running, one is for use with shunt motors and the third is for tach output. There are two pins labeled "Inhibit". When these are shorted, the output is stopped. This happens when the FWD/BRK/REV switch on the front panel is in the BRK position. I verified it with a meter.
6. I don't have a schematic diagram, so I can't find where to probe for different voltages.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
Go to the KB drive site, they have manuals and some schematics.
Those are Triac bridge drives, there is a current limit resistor in the bridge circuit that often opens up.
Hi Max,

Thanks for responding. I have the manual, but haven't found a schematic yet. I attached the manual.

I have identified certain TECCOR key components;
A68064 - Thyristor Diode 800V
A68063 - NPN High Voltage Transistor
A69258 - SCR
All are in TO220 packages and I haven't been able to find pinouts for any of them. Perhaps they have the same pinout as similar type components, either that or they would not be easy to replace with similar spec'd components.

I am going through the circuit looking for open circuit resistors and haven't found one yet.

Scott
 

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MisterBill2

Joined Jan 23, 2018
18,958
There are a lot of jumpers shown. Has it been verified that they are all in the right position, and actually present?

The schematic is evidently not part of the manual, which jumps from page 16 to page 20, with the schematic supposed to be on page 19.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
There are a lot of jumpers shown. Has it been verified that they are all in the right position, and actually present?

The schematic is evidently not part of the manual, which jumps from page 16 to page 20, with the schematic supposed to be on page 19.
I have carefully gone over all the jumpers and believe that I have all of them in the right position.
 

MisterBill2

Joined Jan 23, 2018
18,958
It was worth verifying that you had all the jumpers right, though. The next step would be checking voltages. THat is a bit dangerous because it would be powered at the time. I suggest using a high powered incandescent light as the test load instead of the motor. Just in case something goes wrong. It is a puzzle, though. The first thing to check will be for a voltage across the ends of the speed setting potentiometer. Simpler and safer to check.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
It was worth verifying that you had all the jumpers right, though. The next step would be checking voltages. THat is a bit dangerous because it would be powered at the time. I suggest using a high powered incandescent light as the test load instead of the motor. Just in case something goes wrong. It is a puzzle, though. The first thing to check will be for a voltage across the ends of the speed setting potentiometer. Simpler and safer to check.
Voltage on the speed potentiometer goes from 0V to 11.6V (center to one side. It is probably part of the 12v control circuit. Both the 7812 and 7912 are outputting the correct voltage. Also, the output relay on the right seems to work. When I hit the Run switch, the relay pins close as they should.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
The majority I have fixed, turns out to be the SCR bridge, there are 3 rectifiers and two SCR's
I suspect the same thing. I have checked a lot of components, but with no DC output to the motor, I have always suspected the bridge circuit. There must be a smaller bridge circuit to power the op amps because I am getting +/-15V rails.

I submitted a support ticket with KB Electronics on the off chance that it would help, and yesterday received a reply. I called them and spoke with one of their technicians. We had a great chat and I explained what I have seen, measured, figured out and done so far. He explained that he can't share the circuit diagram and when I told him that I can't find datasheets with pinouts for the SCRs, thyristors and power NPNs (all TO220), he sent them to me. I have attached them to this post.

My next step is to verify that there is no damage, i.e. open or burned tracks, on the back of the circuit board. The technician suggested I check. I don't expect to find anything wrong there.

After that, I need to second source the SCR's and transistors, basically the bridge components. As a shortcut, iIf you have equivalent component numbers that I can get from Digikey, let me know.
 

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Thread Starter

ScottMR

Joined Apr 4, 2024
19
The Littlefuse sheets show the part No's and usually available from Digikey. D8025L etc
I've been looking at the specs for the devices and looking at Digikey replacements and I think that I have found that F7223-ND might work for A68063 and F5231-ND for A68064. Still comparing though. I've been pretty busy lately with other ventures.
 

Thread Starter

ScottMR

Joined Apr 4, 2024
19
That is the diodes, do you need the SCR's?
Hi Max,
For the A68063 and A68064, I have selected Digikey part number F7223-ND). It seems that the 64 had the same specs as the 63.

F7223-ND
D8025LTP
Littelfuse Inc.
DIODE GP 800V 15.9A TO220AB-L

For the A69258 SCRs, I don't have a Digikey number yet. If you can verify my selection for the diodes and give me a part number for the SCRs, I'd really appreciate it.
 
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