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VFD Problem

09/02/2017 7:38 AM

we are using a vfd, when we increase the frequency upto 37 hz, it is working fine.if we increase above 38 hz the voltage will raise upto 670v between phase to phase & vfd trips.
what may be the problem, please suggest.

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#1

Re: VFD Problem

09/02/2017 11:28 AM

I assume you are driving a motor. A motor is an inductive load, i.e., the impedance is proportional to frequency. VFDs ramp up the voltage as frequency is increased to limit current draw on start-up (low frequencies).

The VFD needs to be programmed to match the particular motor you are driving (see the motor nameplate and your VFD manual for details). It appears that your VFD is not programmed correctly (voltage per hertz is too high) and maximum voltage is reached before operating frequency.

https://www.wolfautomation.com/blog/basic-vfd-programing-tips/

Another possibility is that the motor is faulty or not connected correctly.

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#2

Re: VFD Problem

09/03/2017 8:38 AM

@TSR, is this a system that was working perfect before and went faulty or is it a new instalation by someone just starting up on VFD's. All important info that is neede for advice.

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#3

Re: VFD Problem

09/03/2017 2:43 PM

Drive Make, Model, HP, rated Volts, Amps, application

Motor NP data.

What instruments are being used to measure voltage - are you inadvertently measuring the carrier voltage of the PWM?

Is this a new problem (Fault) or a new install with problems?

If it was running fine and not now, verify your parameters didn't get lost.

If parameters OK - replace drive.

If it is a new install follow the correct startup procedure. If still a problem contact technical support.

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Member

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#6
In reply to #3

Re: VFD Problem

09/06/2017 3:07 AM

Thanks for reply.

the details are as follows.

DRIVE:

TECO SPEECON 7200MA SENSORLESS VECTOR.

JNTMBGBA0075AZ-U

AC 3 PHASE 380-460 V, 50 HZ.

AC 3 PHASE 0-460 V, 110KVA, 128 AMP.

MOTOR:

AC 3 PHASE INDUCTION MOTOR.

TECO MAKE.

TYPE : AEEF, 8 POLES.

OUTPUT 60 HP, 45 KW, 50HZ.

720 RPM, F INSULATION,

220, 440 V

168, 84 AMP

ROTOR K2, IP64, RATING: CONT,

FRAME 250MC.

*********

Multi meter is used to measure the voltage.

This is a new drive installed few months back. At that time it worked for one week and then started giving problem like over heat. After some time gap, resetting the drive again it started working.

Next the ground short problem started coming. At that time voltage between phase to phase is more than 600 v & drive trips.

Thanks.

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#7
In reply to #6

Re: VFD Problem

09/06/2017 8:05 AM

TSR, I will suspect that the original parameters were wrong and that it may have damaged the Drive or even the motor. It looks like a matched pair from the manufacturers side and I will suggest that you get the agent that sold you the set to bring their Technical adviser to help you. A few month instalation sounds like a guarantee involvement and any action from you may cost you an invalidation of the guarantee.

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#8
In reply to #7

Re: VFD Problem

09/06/2017 4:17 PM

Off topic?

It is ON TOPIC!

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#9
In reply to #6

Re: VFD Problem

09/06/2017 4:22 PM

I totally agree with Oomborie.

My suspicion is you have a damaged motor. Have it checked out.

If the drive was setup incorrectly it could aggravate motor / drive damage.

Check with your technical support for the motor / drive. If it was commissioned by a recognized technician you should have warranty - as long as you did not abuse the equipment.

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#10
In reply to #6

Re: VFD Problem

09/06/2017 9:39 PM

Again, you are leaving out information. I feel like a dentist, pulling teeth from you with a pair of pliers.

What is your incoming line voltage? That drive is capable of anything from 380 to 460VAC input.

Where are you measuring the 600V? On the input side or the output side?

If you are meaning that the LINE voltage is measuring 600V phase-to-phase on the input side, then that is your problem right here. The VFD is not increasing the line voltage, it cannot do that. The 600V is coming from somewhere else and the VFD is not going to handle that (it may already be damaged now). You cannot allow 600VAC to get to it. You must find out why you are getting 600VAC on the line.

If the 600V is what you are measuring on the OUTPUT side of the drive, that is no unusual. Attempting to read the complex waveform on the output side of the VFD requires very expensive scopes, not cheap hand-held digital multimeters.

That motor can be connected for 220V or 440V. How do you have it connected? (this also relates to what voltage you are using for the VFD). If you are using 220V, then the VFD is too small because that motor is going to require 168A and the VFD is only rated for 128A. If you are using 440V, then your VFD is sized correctly.

If you are using 440V but the motor is connected for 220V, that is never going to work correctly.

But if you are feeding the VFD with 380V, then that motor is not going to get enough voltage, because the VFD cannot make voltage that is not there. So if, for example, you have a 380V input and a motor rated for 440V, that means the maximum frequency you can give that motor without starving it for torque is 43Hz. Once you go over 43Hz, the motor will begin to lose torque, slip will increase and it will draw higher current, possibly overloading the motor. The drive then might be programmed to fold back the frequency in order to limit the current to the motor nameplate value, which might explain why your maximum frequency is ending up at 37Hz.

Bottom line, you have parts that don;'t match exactly; the VFD and motor. The issues can be overcome by someone who understands them and can properly program the drive to compensate, but that's a longshot from what I see here...

Whew... I'm exhausted... Someone else take it from me, my hands are cramping on the pliers.

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#11
In reply to #10

Re: VFD Problem

09/07/2017 5:36 AM

You guys have scored me off topic but this company and its employees are out of their depth just looking at the info provided. This unit should still be under warentee and the chances are that it will just be destroyed if left to the people there. They need help and it is going to cost them what ever way they go.

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#13
In reply to #11

Re: VFD Problem

09/12/2017 12:29 AM

NO, NO!

We have scored you ON TOPIC! With another 4 it will be ON TOPIC!

YOU posted as OFF TOPIC - I could not believe that - perhaps you miss keyed.

When you volunteer OFF Topic as you post it starts with a score of 5 OFF Topic.

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#14
In reply to #13

Re: VFD Problem

09/12/2017 3:56 AM

Thank you GW, what a slip of the finger/mind. Not sure which one, ha ha, years catching up on me. Must have thought that I am scoring myself some good answer there.

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#15
In reply to #14

Re: VFD Problem

09/12/2017 11:28 AM

I almost did that myself a couple times.

I drove through a stop sign the other day - kind of shook me up - don't like making those mistakes - it can kill you.

So I went back to analyze why.... the stop sign was only half of standard height - so not where you expected. There was a bush that partially obscured the sign at the distance you usually make the decision to start slowing down / braking. The white stop line was almost totally worn off - only a hint of it, and at night (when I did the oopsy) it was nearly invisible. I was very tired - 18 hour shift starting up equioment and I was still preoccupied --- Sounds like excuses - but everything added up and mentally the sign was ignored. Luckily I recognized the issue after the fact - and this time there were no repercussions.

Long winded, but if you examine why you made the selection - then perhaps the selection box is not inherently at a glance indicating what the choice will be ???

After all the box starts with "Yes" and "likely" - if it was instead "Off-topic" and "not associated with the conversation" ???

And I am going to select off topic

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#12
In reply to #10

Re: VFD Problem

09/07/2017 5:54 AM

JRaef, thank you for this information. What you are doing is teaching the OP on all the specifics of using motors and VFD's. This will come in handy with their next installation to know that there is much more than just conect and run. It will unfortunately not help them to save or rectify the present problem. I'm sure that their plant cannot wait a week or longer to get it going. All additional information is irrelevant to their present problem, they do not have the combined knowledge to rectify this pressing problem and that is to get the plant up and running now.

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#4

Re: VFD Problem

09/03/2017 5:29 PM

You don't say what your line voltage is to begin with, you don't say what the motor rates voltage is, you don't say where you are measuring the voltage increase, you don't say what you are measuring it with, you don't say what size motor and drive you have or what the load is. In short, you supplied about 1/10th of the necessary information needed to even begin to diagnose anything.

Help us help you...

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#5

Re: VFD Problem

09/03/2017 5:57 PM

TSR it is impossible to talk to each other without you coming back to YOUR thread.

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