[imsly2]

I'm in the process of hooking up a Rotary phase converter. I ran a new electrical drop to the machine and was testing it out.

I was only testing out single phase at first. Inputs on L1 and L3, no jumper or anything on L2.
This was ran straight to the Mains, not through the RPC at all, which is how I had it wired and running initially

Turned on the machine and everything was working as it should, homed it out. Jogged the axes around and then went into MDI to turn on the spindle. M3 500

As soon as I hit, "Cycle Start", There was a, "POP" and the machine started smoking. Control was still on. I ran around back and cut power.


Looked around and didn't see any carnage, so I was thinking maybe it popped a fuse or something. Bumped the power back on and pretty much immediately smoke started rolling off the large component hooked up to the VFD.


Attachment 291212


Okay, so my first question is.. what is that thing? (Edit: It's the Spindle Braking Resistor)
Edit: The VFD screen was on and displaying EF3 (can't remember if this is the normal start up text..)

Not really sure where to go from here at all, should I disconnect the VFD all together and bring the machine back up to see if there's any other damage?
Is this what happens when a VFD dies? or is it possible this large black component itself has failed?


Any help would be much appreciated!!

[imsly2]

Okay. I managed to find some electrical drawings online.

The component that is smoking is a:

SPINDLE BRAKING RESISTOR
150 OHM - 225 WATT


I disconnected and measured the resistance and I'm only showing 15 OHM, not 150.. Pretty sure I'm in the right scale?
Not sure if the resistor is bad or if the VFD is dumping too much power to it for some reason.
I Especially don't understand why it would be sending power as soon as I flip the breaker. I thought the VFDs powered up with an alarm and you had to hit reset on the machine before they would do anything.



Attachment 291216

[imsly2]

With the Resistor disconnected, I powered on the machine and measured the B1 and B2 terminals on the VFD (terminals that go to the spindle braking resistor).
As soon as it gets power, I'm seeing 700-800VAC on the multi-meter. I'm guessing that's a false reading from the VFD pulsing? So I don't really know if that's abnormal..

Anyone have any suggestions on what to try next?

[allen mullis]

So you fried your VFD. That one is obsolete, a good replacement would be a yaskawa F7, at least that is what I have swapped out for on mine. I have to wonder if something was bridged to run on single phase, but it is neither here or there, bottom line is the drive is fried and obsolete. It could be fixed as anything can be, but not worth it. Yaskawa Electric Varispeed F7 CIMR F7U27P5 27P51E 12KVA 31A and Manual | eBay this would be a good replacement, highly over rated for the amps you would need, but that is a simple parameter change to keep from over powering the motor. You can make a big drive run a little motor, but not the other way around.

With the Resistor disconnected, I powered on the machine and measured the B1 and B2 terminals on the VFD (terminals that go to the spindle braking resistor).
As soon as it gets power, I'm seeing 700-800VAC on the multi-meter. I'm guessing that's a false reading from the VFD pulsing? So I don't really know if that's abnormal..

Anyone have any suggestions on what to try next?

[xjdubber]

sounds like you used the generated line from rotary phase converter to power the machine, which in turn blew up the VFD. if you buy an oversized vfd use it to generate your 3rd phase for the spindle only and forget about the rotary phase converter.

[imsly2]

The rotary phase converter was not connected/turned on at all during this test. It was only the single phase 240 from the main lines ran to L1 and L3 on the machine without any jumper to L2. I mentioned me running a new line for the use with 3 phase power, but don't want it necessarily to be confused with the causality of this problem. Specifically, because that has led me down the wrong road in diagnosing things in the past.

I've learned through research that 3 phase variable frequency drives driven with single phase power can fail. It IS a new electrical line, but only currently connected to single phase 240 power on the L1 and L3 inputs on the machine. I have double and triple checked this to make sure I'm not doing something silly to cause this problem. If you can think of something wrong I could have done with hooking up single phase power to these inputs that might have caused this problem than I am eager to hear you out. If you think that me hooking up single phase power to this 3 phase variable frequency drive has caused this failure it is important to me as well.

I just want to know about this specific mode of failure and any other ways I can further test to prove that the VFD has failed and needs replaced vs. any other potential problems.


Thank you for your input!!
-Sly2

[allen mullis]

the only thing on the machine that uses L-2 is the VFD, everything else comes off the control transformer. The control should go through a line stabilizer and the DC should be fed directly from the outputs through a bridge rectifier and the caps, then the drives. If you just wanted to move it around, you could plug it into a 110 wall outlet. You need to check to see where L-2 is going. Since you are running a rotary converter, L-2 will be a "wild" leg unless there is another load somewhere else to stabilize the voltage. For example, if you check L-1 to ground, you should see 120V, If you check L-2 to ground, you should see 240V IF THERE IS ANOTHER LOAD SOMEWHERE, if there is not, you might see 270 V or higher. This is why an idler motor is recommended, just something to give the juice somewhere to go. It is possible that this caused your problem. I recommend a phase perfect digital converter, I run one and regardless of load the voltage stays within 1 volt leg to leg or leg to ground. Expensive, but worth it. If this is your only 3 phase machine, then replace the drive with one of your choosing and run it on single phase.

[xjdubber]

The rotary phase converter was not connected/turned on at all during this test. It was only the single phase 240 from the main lines ran to L1 and L3 on the machine without any jumper to L2. I mentioned me running a new line for the use with 3 phase power, but don't want it necessarily to be confused with the causality of this problem. Specifically, because that has led me down the wrong road in diagnosing things in the past.

I've learned through research that 3 phase variable frequency drives driven with single phase power can fail. It IS a new electrical line, but only currently connected to single phase 240 power on the L1 and L3 inputs on the machine. I have double and triple checked this to make sure I'm not doing something silly to cause this problem. If you can think of something wrong I could have done with hooking up single phase power to these inputs that might have caused this problem than I am eager to hear you out. If you think that me hooking up single phase power to this 3 phase variable frequency drive has caused this failure it is important to me as well.

I just want to know about this specific mode of failure and any other ways I can further test to prove that the VFD has failed and needs replaced vs. any other potential problems.


Thank you for your input!!
-Sly2

I understand now, when you originally had this hooked up, did you have a jumper between L2 and one of the other. You mention a code displayed on the drive, do you have the manual for the drive that shows the explanation of this code? Measuring 700 ~ 800 v should be impossible no matter how the drive is pulsing, also at standstill (drive disabled) there should be no voltage at the brake resistor terminals. If there is the internal circuitry of the drive is damaged.

Properly sized vfd for single to three phase do not fail any earlier then any other vfd would.

[xjdubber]

just read the manual for that drive EF3 indicates a fault input at terminal 3 see page 51 in manual

https://www.yaskawa.com/pycprd/looku...4333GPD333.pdf

[imsly2]

Okay, I did some more testing.

With the braking resistor and spindle disconnected I powered up the machine.

The EF3 is the normal fault when you power up the machine. It clears and goes to E00 when you hit reset after powering on the machine.
I can send spindle speed commands and the VFD responds and goes into run mode and receives the speed signal. M5 puts in stop mode as you expect.
I tried this with single phase, then also turned on the Rotary phase converter and hooked up the L2. The inverter acts the same on both.


I tired measuring the voltage at the spindle terminals and wasn't detecting anything, But I think you can get weird readings trying to measure voltage coming out of a VFD? I hooked the spindle back up but not the braking resistor and the spindle doesn't turn with any speed command. Don't hear it humming or anything.

My guess would be it's not sending any voltage. I suppose its possible the Voltage may have to pass through the resistor before it goes to the motor? So by having the braking resistor disconnected it can't send current to the motor.



Anyone have any other ideas of some trouble shooting to try before saying it's dead?

[allen mullis]

It won't burn out any faster on single phase, the drive has built in protections. In my experience, the only times I have had current going to the braking resistor, the drives have been beyond feasible repair. At least it did it while you were close, usually it makes all the insulation melt off the wires, smokes out the cabinet trips the breaker and makes you wonder if the whole electric cabinet is wasted. Still, it is never a good feeling when you let the blue smoke out.

[allen mullis]

BTW, it doesn't send it to the resistor before the motor. The only time the resistor is in play at all is when the spindle is in decel. It is a place to dump and bleed off the energy that must be dealt with to bring the spindle to a stop. It can operate without that in line, but the parameters would have to be adjusted to allow the drive enough time to absorb the energy.

[imsly2]

Anyone tried one of the Fuji Drives?

Fuji AF 300 G11 AC Drive 5HP 230V 6KG1123005X1B1 Excellent Used Condition | eBay

[imsly2]

Okay, I have a theory. Until now I never really looked at the VFD sticker or through it's manual.
The badge on the side of the Partner mill say 240V.. but the Input range for the VFD actually says 200-230V..

Is it possible my voltage could be too high?
My power coming to the house is measuring around 240V during the day. And at night, it jumps up to about 250V

Could 240-250 volts be enough to zap the VFD? Does anyone else have experience with 240 or a little higher giving you problems?