Danfoss FC202 can not reach 50Hz output 1

[Keith1976]

Hi All;

I am using FC202-200kW to run a centrifuge pump (distribution pump). Since I only make use of the soft start and soft stop, I run the inverter in Hand mode and press the '+' button to reach 50Hz output.

But the display show that the maximum is 47Hz and status is RAMPING, not RUNNING.

I check the current and it is still below the current limit.

Does anyone have an advice why this is happening?

Thanks in advance,
Keith

 

[sparkysb]

Keith 1976
You need to check the settings of the VFD for the maximum frequency, it may be set at 47hz. In which case you need to increase this value.

 

[Keith1976]

Sparkysb;

of course the setting is already 50Hz for maximum frequency.

In fact, I was thinking of changing the makx frequency setting to 55hz so that it can reach 50hz in reality???

But is it dangerous for the motor? Motor spec is 380V, 50Hz.

One information though, the incoming power supply is 400V 50Hz. They cant get exaclty 380V out of the transformator

Keith

 

[sparkysb]

Keith 1976
Ok just checking! Even though the vfd input is 400volts the rated motor voltage should be set to 380volts within the vfd. Also the rated frequecy of the motor 50hz is at 380 volts the vfd can change this ratio and run the motor above 50 hz without damage there just becomes a point where motor torque begins to reduce.

 

[sparkysb]

keith 1976
At least I belive there is no risk of damage to the motor! Somebody else may be able to confirm this for you keith. Overspeed could be an issue for the pump also!

 

[Keith1976]

sparkysb

Thanks.

hmm....yes, I am monitoring the current as well.

Extra 3 Hz for a 4-pole motor is about 9 rpm extra???

Keith

 

[roydm]

Is it possible that the VFD senses a motor overload so it limits the frequency to 47 Hz? You could try throttling back on the discharge to see if that lets it get up to speed.
Roy

 

[Keith1976]

Rodym;

But the current reading shows around 260A while the limit (motor name plate) is 318A.

Keith

 

[ScottyUK]

Yes, but the drive can't read the motor nameplate: is there an internal drive parameter which is set to too low a value and the drive is reaching a limiter before reaching base frequency? You'll probably have to sit down with the manual and go through the parameter list to find the reason. Some drives have a couple of binary registers which hold diagnostic information which might set a digital flag when a limiter is active, otherwise you'll have to do it the hard way, parameter by parameter.


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If we learn from our mistakes I'm getting a great education!

 

[Keith1976]

ScottyUK;

That really makes sense. I checked it out, the customer set the current limit value at 318A exactly.

Is it safe if it is set to let say 10% higher than nameplate?

Thanks

Keith

 

[itsmoked]

You really should sit down with the manual and step thru all the many values. You can have many different settings that could accidentally cause the limiting you are seeing, not just the current limit.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Keith1976]

Itsmoked;

I reset the inverter to factory setting already. Then enter the "principle" setting only, i.e. motor data.

Keith

 

[Keith1976]

Hi All;

Thanks for the advice. The problem solved. It turned out that the motor-pump coupling is not properly installed.

Hmm....then this must be a good feature of Danfoss inverter.

Keith

 

[ozmosis]

Keith1976
Good to see you got the issue sorted.
It might be worth running a function called AMA (Automatic Motor Adaption) parameter 1-29, assuming all the motor settings are correct. This means read the motor values off the nameplate and input as per the data in parameters 1-2*. If the voltage and current are not correct as per the motor requirements and especially if the motor voltage is more than is available, then it really does cause problems with the current limit functions. AMA is an internal 'tuning' from the VFD to the motor based on the motor details correctly input and then the measurement it makes of the motor circuit.
In your case you had more volts than the required in the motor to the current rating so the VFD will compensate for this.
Current limit is not always based on the maximum current. The VFD will determine the current limit profile based on the speed/frequency it is supposed to run at. So, just because you have 318amps rated maximum it doesn't mean it reaches this before it does something. If the current is rising higher than a level it should be doing at a certain frequency, then it will go into current limit. This is especially true with motors that are connected to a load that would be a variable torque and motors that have cooling from their fan that is not force ventilated (majority of motors).

 

[edison123]

How exactly was the coupling problem here ? Could you please expand a bit ?

Muthu

http://www.edison.co.in

 

[Keith1976]

Ozmosis;

Thanks.

I always do AMA at least once when I test-com an inverter. But after that I do not do it anymore unless I press manual-initialization to return to factory setting

Edison123;
The vendor who supplied the motor came in and notice that his men did not do perfect aligning. So they redo it.

Keith

 

[edison123]

Thanks Keith.

But still I don't see the connection between proper aligning and the drive output limiting itself to 47 Hz.

Muthu

http://www.edison.co.in

 

[Marke]

Hello edison123

If the pump alignment is not good, the load torque will be modulated as the motor rotates depending on the type of coupling.
Although the current appeared to be less than the maximum setting, the current would be amplitude modulated and the maximum current will be exceeding the maximum setting, causing the frequency to be reduced.
You would need to use an analogue clamp meter on the output cables to see the current swinging.

Best regards,
Mark.

Mark Empson
L M Photonics Ltd

 

[edison123]

Hello Marke

Got it. As usual, the hour produceth the man.

Thanks.

Muthu

http://www.edison.co.in

 

[Keith1976]

Marke;

Yes, we used analog one that time to prove it to the motor vendor.

May be that is also the reason why it keeps showing RAMPING instead of RUNNING

Keith