vfd turns on hertz but no voltage or amperage

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Cliff In Orlando said:
The drive is on and ramps up to 38.6 hertz. Everything else is good. Run command is there. The drive says it is running and indicates the hertz. Scroll thru the display options and shows 0 amps. Checked the amps with a fluke 33 and it shows 0 amps. Checked output voltage at U2 V2 W2 and shows no voltage phase to phase or phase to ground. Input voltage on U1 V1 W1 is 480 volts. Everything is working correctly on the machine and the drive except not sending voltage out from the drive.
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This is an example similar to that I have mentioned on another thread.
It refers to well-intentioned response to (hopefully) help the OP.
However, somewhere along the way—it becomes an adversarial comment that draws ire from OP.

There is a lot to consider and come up with an answer but if I were the engineer to respond to the question—I would be hesitant to offer my heuristic approach in solving the problem-- to avoid being labeled: “know-nothing doofus”.
I have quite some experience on VFDs under my belt and I've seen problems like this before.

Reminds me of Mark Twain’s comment:
“It is better to keep your mouth shut and let people think that you are stupid--than open your mouth and remove all doubt.”

I’m happy sitting quietly in my rocking chair, reading comments and allowing others offer their solution.
Best
 
Cliff In Orlando said:
The drive is on and ramps up to 38.6 hertz. Everything else is good. Run command is there. The drive says it is running and indicates the hertz. Scroll thru the display options and shows 0 amps. Checked the amps with a fluke 33 and it shows 0 amps. Checked output voltage at U2 V2 W2 and shows no voltage phase to phase or phase to ground. Input voltage on U1 V1 W1 is 480 volts. Everything is working correctly on the machine and the drive except not sending voltage out from the drive.
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As a general rule, if the drive is not connected to the motor, and the drive is in V/Hz control mode, it does not know whether the motor is connected or not, it ramps up the output frequency without regard to what happens at the motor. When a drive is in Sensorless Vector Control (SVC) control mode, the drive is WATCHING the motor, so it would give you a fault code telling you that there is no movement in the motor. So the fact that you didn't get an error / fault on the drive indicates that it must be in simple V/Hz mode. So again, in that mode if the motor is not connected, it will act EXACTLY as you have described. The motor is PART of the circuit, so it would not be unusual for you to not read an output voltage on a drive that is not connected to a motor. Hence my suggestion of the open disconnect switch, which is a VERY common issue. So if it is not the switch, then another possibility is that the motor terminations are not made (that happens too). I would double check the peckerhead.

If it's not that, then the drive is dead, the transistor firing is not taking place. There is no recovery from that, you have a dead drive. Small drives like the ACS355 are not repairable, they are throw-away. There are no discrete transistors any more, they are all integrated into a potted block with the line side diode bridge and the firing circuits, called an "IPM" (Intelligent Power Module) that is surface mounted to the main printed circuit board.

Technically you can buy an IPM and try to replace it if you have mad soldering skills, but on the two that I tried, it was a total waste of time, I could not match the mechanized wave-soldering process used to manufacture them. So if you tried, the IPM would cost you about 50% of the price of an entire new drive, then you will spend hours trying to swap it out, only to (per Murphy's Law) discover that something else was wrong anyway (or also).
 
Cliff In Orlando said:
Ok so I got on here thinking people would actually help here. All the basics have been checked and verified. Motor is hooked up. Motor has been ohmed and checked for any leg grounded and it is good. All safety switches are working and it turns on like it is supposed to but does not send voltage out from the drive. Voltage is being checked with a fluke 87V. Pretty sure that meter is pretty accurate. If you don't know the answer or have never seen a situation like this then why even respond. I have been doing industrial electrical work for over 20 years and this is the first time I ran across an issue like this. Was just hoping someone would actually be helpful with real answers.
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Two of the people that responded, Jraef and Besoeker3, know more about drives than the rest of the forum combined, so I would not disparge their advice...
 
cpickett said:
Two of the people that responded, Jraef and Besoeker3, know more about drives than the rest of the forum combined, so I would not disparge their advice...
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That is very kind of you..................)
 
It seems likely if the drive ramps up from 0 to 38 Hz that it is enabled and getting some kind of control signal.

If there is no voltage at the drive output terminals I would suspect the drive, but usually when a drive fails, especially a fairly modern drive like this, you get some kind of fault code as the drive will catch the fault. Did someone by any chance attempt to improve the operation of the drive by changing some part of the configuration? Like somehow putting it in current control mode?
 
Cliff In Orlando said:
The drive is on and ramps up to 38.6 hertz. Everything else is good. Run command is there. The drive says it is running and indicates the hertz. Scroll thru the display options and shows 0 amps. Checked the amps with a fluke 33 and it shows 0 amps. Checked output voltage at U2 V2 W2 and shows no voltage phase to phase or phase to ground. Input voltage on U1 V1 W1 is 480 volts. Everything is working correctly on the machine and the drive except not sending voltage out from the drive.
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Can you read continuity through motor leads? (may need to disconnect from drive when testing)

Could even temporarily connect a small motor if you have one easily available as a test load in close proximity of drive to see if it will drive that motor.
 
hbiss said:
Looks like Cliff either had enough of us or found out that one of us was right. He hasn't been around since yesterday.

-Hal
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Occasionally get someone that don't like to be questioned, just wants an answer.

I feel I know a lot about many things, still overlook something I maybe should have known to look at occasionally.
 
Misconfigured.
You are seeing the reference speed (the setpoint). It needs a Start command. Put it into Keyboard mode and manually run locally from the VFD. I suspect you will see your motor spin. Review the config settings, which I know can be quite confusing if you are not very experienced with programming VFD's.
Most manufacturers have a few commonly used quick set-up configuration examples that you could probably use for your application.
 
The VFD display should tell you the mode that it is in. If it’s stopped then you don’t get an output. What you see on the screen may be an actual output or just a speed reference...how fast it should go IF it is running.

If this is the only make/model you deal with then study the little status indicators on the screen. If you work with several different ones it’s easier and faster to just check the IO settings and the IO monitor/diagnostics menus first after doing basic electrical checks. This may include switching to keypad mode to eliminate input problems.

Check in the monitoring and diagnostics menus. Check what your digital inputs are and what it thinks your output is, Check the IO menu to determine what the various IO should do. Compare these and it should be obvious what the problem is. That’s what someone with 20 years of experience including VFDs would do.

Because of how flexible they are most VFDs can have any input programmed to do anything and there are multiple ways to do things. For instance you could have DI1 and DI2 programmed as 3 wire start and stop. Or as forward and reverse 2 wire fun. Or as 2 wire run and forward/reverse. And you can have other inputs as enable, base block, E-Stop, etc. So taking the first 2 in 3 wire mode loss of either input prevents it from running. In 2 wire mode it is a little different. You get the idea. AND you need to know if it’s 120 VAC (rare these days) or 24 VDC sourcing or sinking. And even if you know all that it could still be a burned out input so the only way to know for sure what is happening is via the monitoring/diagnostic menu, assuming it’s a run input command issue. It takes me about 15 minutes with an unfamiliar VFD to figure out what’s going on and most of that is pushing buttons.

The fact that you said ohmed out a motor says something. Were you checking continuity of doing a milliohm test? Or insulation resistance? Two of these tests are diagnostic. One is almost utterly useless. With 20 years of experience you should know which is which. I’ll give you a hint...which tests does your motor shop do?

Then we have the issue of whether or not it is getting the correct speed command which again requires looking at the settings and the inputs as the drive sees them. VFDs have multiple references so you need to know which one(s) it is reading.

Then we can do similar things with the outputs.

This may sound very complicated to a first year but it’s not. You just have to take the time to learn how a VFD works.

As suggested putting it in keypad control bypasses troubleshooting all the inputs first and verifies if it is a drive output problem or just an IO issue. But some VFDs continue to follow enable or Stop so keypad mode alone may not be enough. Another gotcha you learn after a few years.

At the end of the day though VFDs are very similar for the most part. You need to know how it works to troubleshoot it. Your answers say you don’t and since you’re not listening you better call someone that desks with VFDs. ABB VFDs are quirky and support from Berlin is crap. ASEA has always been a bad influence on the company. Back when it was Brown Boveri, Baldor, Robicon, etc., different story.

As to 20 years of experience I’ve met guys like you. They don’t listen. Multiple responders said to check the output at the motor or at the drive, something your first post never mentioned. Then the suggestions are to either bypass inputs or check inputs, again something you never did. The first rule of troubleshooting is that you compare what you observed to what is expected, Then you look for what is causing it. Do you replace a breaker when if trios without looking for what caused it? That’s what first years do.

So with 20 years of experience most people have a progression. They have experience like 1, 2, 3...20. In your case yours is more parallel and you are still making first year mistakes. So it’s more like 1, 1, 1..,1. See, 20 years of experience, all first years, I’ll bet you change breakers because they trip, too.
 
Does the VFD have DC Buss Voltage?
I have an Emerson VFD just took out 2 weeks ago same thing
The times I have seen this it was:
I have found older VFD with internal fuse located in side the housing. Apparently not meant to be easily field changed. (Don't remember which ones)
I have had the IGBT (Drive transistors) fail open, although they usually fail closed. (AB, ABB, ADC, SD, pretty much any manufacture)
I have had Main control boards go bad. The the transistors that drive the IGBT go bad. (ABB ACH440 and AB PF753)
 
Jraef,
I know this is old and the OP is long gone but is it possible that the overload tripped either in the drive or if it has one in the bypass assembly? I would imagine it would throw an alarm but I'm not sure, particularly if it was in the bypass section.
 
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