What about the condition of the motor ? OR its attached mechanical things , system

[phatcreators]

What about the condition of the motor ? OR its attached mechanical things , system
The data is collected from the VFD display when the motor was running :

The drive & the VFD has the capacity of 11KW

The set speed or speed command given was 100 m/min via HMI (Touchscreen LCD)


Frequency Reference : 48.83 Hz

Output Frequency : -50.10 Hz to -50.82 Hz (Not stable , fluctuating between this range)

Output Current : 16 Amps to 16.8 Amps (Not stable , fluctuating between this range)

Motor Speed : - 47. 50 Hz to -50.37 Hz (Not stable , fluctuating between this range)

Output Voltage : 405.5 V to 408.2 V (Not stable , fluctuating between this range)

Output KWatts : 20 KW to 22 KW (Not stable , fluctuating between this range)

DC Bus Volts : 544 to 548 VDC (Not stable , fluctuating between this range)

Torque Reference : -135 % to - 150 % (Not stable , fluctuating between this range)

thanks

 

[FvM]

Mechanical overload condition.

Sounds like a replay of a previous post.

 

[phatcreators]

which one (the given data) tells that there is mechanical overload condition ???

 

[chuckey]

"Output Frequency : -50.10 Hz to -50.82 Hz (Not stable , fluctuating between this range)" this is the cause of all the other readings varying. this is set by a variable frequency oscillator within the VFD. Its frequency can normally be set by a potentiometer - is this noisy, give it a blast with switch cleaner, or it could be set by an external control that is picking up noise on its wiring loom- try disconnecting it. Could be that there is hum on the supply to the oscillator, check this with a CRO.
Frank

 

[munzir]

"Output Frequency : -50.10 Hz to -50.82 Hz (Not stable , fluctuating between this range)" this is the cause of all the other readings varying. this is set by a variable frequency oscillator within the VFD. Its frequency can normally be set by a potentiometer - is this noisy, give it a blast with switch cleaner, or it could be set by an external control that is picking up noise on its wiring loom- try disconnecting it. Could be that there is hum on the supply to the oscillator, check this with a CRO.
Frank

What do you mean by :

" Its frequency can normally be set by a potentiometer " (What value should i set for this ? Where to connect the pot. for setting this frequency oscillator ?)

" give it a blast with switch cleaner, or it could be set by an external control that is picking up noise on its wiring loom " .
Do you mean that clean its contacts with degreaser or contact cleaner ?

What is a CRO ? where to connect this CRO ? And when to connect , when the VFD is off or power on ??

thanks though very much indeed

 

[dineshdeshmuk]

How can the 11KW motor & 11KW drive be run on 20KW to 22KW output ??? How is this possible ?

Its windings should be worn out ???

 

[FvM]

How can the 11KW motor & 11KW drive be run on 20KW to 22KW output ??? How is this possible ?
Its windings should be worn out ???

It's possible, may be for 1 minute or 2. Presuming a correct parameter setup, the VFD will stop the overload situation after a specified timeout period.

I was referring to the below quoted previous thread that discusses a similar situation. It also discusses possible ways to narrow down the overload cause.

https://www.edaboard.com/threads/258057/

As an additional comment, you shouldn't overrate the fluctuating motor speed when the VFD is apparently operating at it's dynamical power limit.

 

[munzir]

why the motor speed and other parameters are fluctuating too much ?

 

[FvM]

why the motor speed and other parameters are fluctuating too much ?

A plausible explanation is that the VFD is cutting motor power because a limit value is reached. That can easily result in fluctuations.

It could be also the mechanical load, e.g. a defective ball bearing that causes a fluctuating overload. Or any kind of VFD defect.

To ask a question in return, how is the machine working at low speed settings, e.g. 10 or 20 %? Is it the VFD still in overcurrent and the speed fluctuating? In this case, how's the motor working when decoupled from the load?

 

[phatcreators]

Machine works well at low speed i.e. its amps are within range but doesn't run at all well during its middle speed range (but during this middle speed range the motor takes too much amps than the rated one and trips after a minute or 2)

But in the stated set speed i.e. 100 m/min , you can see that the motor is taking normal amps almost 50% amps of the rated one.

Why is amps are well withing the range but not the other things like output kilowatts and the other parameters are fluctuating a great deal without stabling a little

 

[FvM]

I'm not sure which current is displayed. If it's phase current, than it doesn't fit the other values like torque and power. Either currrent or power and torque are wrong. This suggests a defective VFD.

- - - Updated - - -

I'm not sure which current is displayed. If it's phase current, then it doesn't fit the other values like torque and power. Either currrent or power and torque are wrong. This suggests a defective VFD.

 

[phatcreators]

what do you mean by which current ? The VFD says its a output current , and it almost same as the phase current because i measure the Amps with clamp meter (tongue tester) on each phase and its almost tells the same amount of current on each phase that is 16 Amps to 16.8 Amps .

so it means that there's no mechanical problem but there must be a defective VFD ????

 

[chuckey]

"What do you mean by :

" Its frequency can normally be set by a potentiometer " (What value should i set for this ? Where to connect the pot. for setting this frequency oscillator ?)" The secret is in the name :- VARIABLE Frequency Drive, so if the frequency is variable, there must be some device for varying the frequency, in your case, its varying the frequency when it is not required.

" give it a blast with switch cleaner, or it could be set by an external control that is picking up noise on its wiring loom " .
Do you mean that clean its contacts with degreaser or contact cleaner ?
Contact cleaner - does this mean that you have found it?
What is a CRO ? where to connect this CRO ? And when to connect , when the VFD is off or power on ??
Cathode Ray Oscilloscope. switch of and isolate the VFD. Locate the low voltage DC that feeds the oscillator. This is often 5V, ensure that the -ve side is connected to the earth. Connect your CRO live to the +ve, earth to - ve. Switch VFD on, ensure the +5V is between 4.75 and 5.25V on the DC setting of the CRO. Switch the CRO to AC, increase the gain make sure the hum and noise on the 5V is less then 10mV p-p.
Frank

 

[FvM]

so it means that there's no mechanical problem but there must be a defective VFD ????

I never experienced a case where a VFD calculated wrong measurements. It looks like a software bug, or may be a combination of inconsistent parameters. I would telephone/mail manufacturer's support and ask "how can it be".

 

[phatcreators]

What do you think FvM , where the problem lies in the VFD or in the motor and its associated mechanical setup and system ?

 

[chuckey]

phatcreators , can you explain to me how a faulty motor will change the oscillator frequency?
Frank

 

[FvM]

There's most likely no "changed oscillation frequency". It's normal overload behaviour of a VFD inverter, that it slows down the speed when it limits the output power. Detail behaviour may be different, but a similar overload handling can be found with many drives.

As I already mentioned, except for the confusing current measurement, the observed behaviour could be well explained by regular overload or a defective motor. But the contradictory measurements suggest an inverter problem.

 

[munzir]

Should i replace this 11KW drive with a good working 11KW drive to get to the exact problem ?

 

[FvM]

Should i replace this 11KW drive with a good working 11KW drive to get to the exact problem ?

If you have the option, this should help to narrow down the problem.

 

[munzir]

any brand can i use ?