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Old 05-08-2019, 11:02 PM   #1
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Default VFD run motor is tripping breaker

VFD220B23A is being used to run a 25 HP motor. It is fed by a 125 amp breaker. The reported problem is that it is tripping the breaker at full speed. It can run at 3/4 speed and runs just fine with no issues. This seems strange to me that it would not throw a fault code and shut down motor. I have not been on site yet but thinking maybe VFD is compromised in some way, because this does not make much sense to me why breaker would trip. Current should be ramped on startup and should have thermal protection through J on motor and also through VFD. I don’t see it being a short circuit or ground fault if it runs at 3/4 speed all day long and only shows up when trying to run it at full speed. Any thoughts would be greatly appreciated.
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Old 05-08-2019, 11:35 PM   #2
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Might not be the issue. but recommended breaker size is 175 based on manual.

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Old 05-09-2019, 12:12 AM   #3
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The customer went out of his way to state that does not think breaker is the issue because he has another one running the same motor and it runs full speed just fine. My thoughts are that both VFD are stated to come out of a 200 amp which might be an oversight on original installation if that be the case. Almost would think there should be separate 200amp panels feeding the VFD/motor loads. I appreciate your ability to pull out info on breaker size. Can you send a screen shot of where you got that info. I was trying with no success.


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Old 05-09-2019, 12:14 AM   #4
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Sorry same motor meaning same HP not actually the same motor just identical setup Breaker/VFD/motor setup.


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Old 05-09-2019, 12:24 AM   #5
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What is the power system? 120/208 Y or 240 ∆?

Does it trip right away at 100% or will it run for a while?

The first thing I'd do is a fall-of-potential test across the breaker at 3/4 speed.

If that's good, I'd connect a peak capturing amp meter on each leg and see what the current is at 3/4 speed and 100% speed.
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Old 05-09-2019, 12:33 AM   #6
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Fall of potential test? Are you thinking voltage drop test? It is a 3 phase 200-240 on nameplate of VFD. Good thought maybe voltage comes into play if there is greater length between the one motor that is working and the one with the issue.


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Old 05-09-2019, 12:35 AM   #7
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The customer went out of his way to state that does not think breaker is the issue because he has another one running the same motor and it runs full speed just fine. My thoughts are that both VFD are stated to come out of a 200 amp which might be an oversight on original installation if that be the case. Almost would think there should be separate 200amp panels feeding the VFD/motor loads. I appreciate your ability to pull out info on breaker size. Can you send a screen shot of where you got that info. I was trying with no success.


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In the manual

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Old 05-09-2019, 12:38 AM   #8
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Thanks For info


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Old 05-09-2019, 08:03 AM   #9
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probably a loose connection on the breaker (or bad breaker) so it heats up more than supposed and trips
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Old 05-09-2019, 01:19 PM   #10
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probably a loose connection on the breaker (or bad breaker) so it heats up more than supposed and trips
I agree. The drive is rated for 90A output max. and would trip at anything higher than that for more than 60 seconds. In addition the input current is always lower than the output current, probably no more than 80A input for a 90A output. So there is no way that drive is pulling enough current to trip that breaker without there being a problem like a bad connection or some other reason for a single phased input situation. If there is a loss of an input phase, the input current will increase by 1.732. So taking the 90A output condition, the 80A input current would increase to 139A and would eventually trip a 125A breaker.
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Old 05-09-2019, 10:51 PM   #11
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You guys are pretty good. I went out there today and there were two issues that struck me right away. 1) the VFD is three phase input and three phase output but is being supplied by a single phase 120/240 system. My immediate question is: Is this VFD engineered to be able to do this? All the info I found on single phase input to three phase output required a percentage higher HP and amp output than the actual load. So this is rated 30 HP and feeding a 25 HP motor.
2) this is of lesser concern, and is that something caused the keypad to be be completely shutdown, I did not spend much time there because I need to do homework on first question first.


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Old 05-10-2019, 11:17 AM   #12
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this vfd should not run on single phase at all, if it is, it is normal that it trips the breaker, drives that can run on single phase tells it on nameplate.
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Old 05-10-2019, 12:04 PM   #13
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Starltes it on 2-19
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Old 05-10-2019, 01:24 PM   #14
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this vfd should not run on single phase at all, if it is, it is normal that it trips the breaker, drives that can run on single phase tells it on nameplate.
No actually, any VFD can in theory run on a single phase input, but you must DOUBLE the size of the VFD with relation to the motor in order to have enough DC bus capacitance to handle the excess ripple caused by single phase input. A few VFDs have phase loss protection that is built into the drive and it cannot be defeated, so even though they CAN accept single phase, the manufacturer has chosen to not allow it. Delta is not like that, they don't care.


FG;

If you have a 25HP motor, a 30HP drive is way too small, unless maybe it is never going to run at more than about 60% speed.
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Old 05-10-2019, 01:37 PM   #15
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No actually, any VFD can in theory run on a single phase input, but you must DOUBLE the size of the VFD with relation to the motor in order to have enough DC bus capacitance to handle the excess ripple caused by single phase input. A few VFDs have phase loss protection that is built into the drive and it cannot be defeated, so even though they CAN accept single phase, the manufacturer has chosen to not allow it. Delta is not like that, they don't care.


FG;

If you have a 25HP motor, a 30HP drive is way too small, unless maybe it is never going to run at more than about 60% speed.
Good stuff. I though all had phase loss detection.

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Old 05-10-2019, 01:51 PM   #16
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Thanks for all input. At the end of the day there is a lot wrong with installation. Delta tech service verifies that the drive is only capable of handling a 15 HP motor with VFD220B23A and drive will self destruct with the load. In order to run a 25 HP motor a VFD375B23A is needed this will require a separate two hundred amp feed for each VFD. Owner is going to contact installer and hopefully get them to fix mistake on their part. Thanks


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Old 05-10-2019, 07:19 PM   #17
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Good stuff. I though all had phase loss detection.

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Well yes and no. Most drives HAVE some form of phase loss protection, because of the potential for damaging the capacitors and/or transistors from there being too much DC bus ripple. But because a LOT of people use this inherent phase converter capability, most mfrs allow you to disable it, or detect it differently*. A few mfrs didn't think of that though, so they have phase loss that cannot be defeated (Mitsubishi is one of those, on their 480V drives at least). You can't use those drives for phase conversion then. This has driven those mfrs to change though over the years because it eliminates a portion of the marketplace for their distributors. So now there are fewer and fewer drives that don't allow for single phase input.


* The other way it is done, and Delta is one that does this, is to NOT have direct "phase loss" tripping, but instead, look at the negative EFFECT of a phase loss, the excess DC bus ripple. A-B drives do it this way too. There is a Fault that will say "Phase Loss", but it is detected by looking at the DC bus ripple content and if there is too much ripple, it ASSUMES it is because of a loss of a phase. So if you have enough capacitance on the bus, i.e. double the size of the motor current or never use the motor at more than 1/2 load, the drive may never know that one incoming phase is not there.
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