[curtiskelowna]

Hi all, my name is Curtis.

I am using a kflop/kstep board and have been getting great performance with my initial motor testing. I was testing with a 48V power supply and a nema 34 5.5amp motor. The motor was running great so I installed it on my machine and wired it in with a longer motor cable. Then i turned on my 48V power supply and I saw sparks at the kflop motor terminal. Keep in mind this is before the kflop\kstep was powered. All the current jumpers were installed on axis 0 and I triple checked the wiring.

Heres where I may have messed up, can anyone comment what may have been the cause of the failure?

1. the voltage clamp had two jumpers installed. for my 48V power supply it should have been none installed.
2. my motor spec sheet did not make a distinction between A- A+ etc. my motor wiring is labeled as A A B B not A+ A- B+ B- so its possible the pair polarity was switched. I have wired this setup multiple times like this so if this was the cause it would be weird that it only happened now.
3. when I measure the unloaded voltage of my power supply, it reads 52 volts. is this too high for the kflop to handle? The motor was working perfectly with this input voltage before I rewired.

Now after all of this it appears that 3 of the fetts have been blown open and 5 of the resistors feeding them have blown. No visible damage to the chip. All of this points to a bad wiring issue but I cant seem to find my mistake. Both Kflop/Kstep power on fine but none of the motor outputs work anymore. Now I am going to order a new kstep but I dont want to blow that one too. Where did I go wrong?

Thanks,

-Curtis

[TomKerekes]

Hi Curtis,

Sorry to hear this. The max allowed motor supply voltage is 48V. 52V is clearly over spec but wouldn't have expected that to be enough to cause the failure. What kind of power supply are you using? Regulated or unregulated? Is it isolated from earth/frame GND?

Having no +5V would keep the FETs disabled with no current flow, but the driver chips would still be susceptible to over voltage.

Having the voltage Clamp set to 25V would have caused the voltage clamp to fail or give up quickly so the voltage would go to 52V.

Regarding:

#1 - that is bad. Even with no jumpers installed the supply should be clamped to 49V

#2 - reversing + and - on a stepper will just reverse the direction it rotates. It should not cause any other problem.

#3 - the peak unloaded voltage should be 48V or less.

What are your motor specifications?

Are you sure your wiring was correct? Did you check with an ohm meter from coil to coil and from coils to GND?

Regards

[curtiskelowna]

Hi Tom, thank you for replying.

I am using a regulated power supply that is isolated from frame ground.

The motor I am using is here:
https://catalog.orientalmotor.com/it...y-/pk299-f4-5a

I am quite sure that my wiring is correct but I did not check with an OHM meter. I will do this next time for sure.

Unfortunately my power supply has no voltage adjust so I think it is a bad idea to use the 52V power supply. I am buying a new 12.5A 48V power supply with voltage adjust just to be safe.

I think if I do all that and learn from my mistakes I should be good second time around.

Question: do you think it is odd that all 4 drivers would be not working? Would removing the affected fetts allow the other drives to potentially work?
Question2: is it better to turn the motor PS on after kflop power up or before?

Thanks again for your help, I am happy with the products you have made and I just put an order in for another kflop for a work project.

-Curtis

[TomKerekes]

Hi Curtis,

Actually 48V might be somewhat high for those motors. I like to keep the supply voltage to be 10~20X the nominal motor voltage. Otherwise regulating small currents becomes problematic.

How are the motors wired? Series or parallel? You said they are 5.5A but the spec says 6.5A in parallel configuration.

With KStep set at full 5A and a motor resistance of only 0.33 ohms the motor voltage would only be 1.65V

48V / 1.65V = 29X

But that wouldn't explain a failure with 5V off and FETs off.

It shouldn't matter the order of turning on the supplies. But it probably makes moresense to have 5V on before the high voltage.

Regards