CAN I OVERRUN THE MOTOR TO HIGHER FREQUNCIES? 3

[CARF]

Dear all,

I am a nono in Greece, Europe and have the following question:

We are running a SEW-EURODRIVE 11 kW
type R82 DV160M4
2010.42914/5.01.2001 B3

415 V triangle
20 A
50 Hz

At this moment the pump is taking up only 5 Amperes at 60 Hz through a Danfoss frequency drive.

Q. CAN I OVERRUN THE MOTOR TO HIGHER FREQUNCIES?
(say 100 Hz)

Thanks !

 

[mishlove]

Above the fundemental frquency - 50Hz - the motor looses torque proportionally. ie 50/100 - 0.5
(There comes a point of saturation where the motor will just die and loose any abilty to function)

If the pump is a Variable Torque pump the load increase HP(Cubed)and Torque(Squared).

Take a look at the following link:

http://cipco.apogee.net/mnd/mepaffi.asp

You could increase the speed until the load demand equals the 20Amp motor FLA

Cheers

 

[jbartos]

Suggestion: Is the motor consuming 5A because the pump has the much smaller HP than the motor shaft HP or is it because of some irregularity in the motor-drive circuit?

 

[CARF]

Thanks, here some more info from eurodrive:

You can over speed the motor to 100hz. However by running the motor
above the rated frequency of the motor you will begin to loose torque.
Bearing life will also be shortened due to increase in heat.

P.S. check out the new web site at

http://www.seweurodrive.com

MVD

 

[Marke]

Hello MVD
One possible reason for the pump only drawing 5 amps, is that it may be running in reverse. Another is that the head may be too high for the pump. (closed valve on output) or it may be running dry. These conditions can be very damaging to the pump.

If you overspeed the motor and pump, make sure that the bearings are able to operate at the higher speed. This is of particular importance with two pole motors.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[jbartos]

Suggestion: An additional parameter that may become very influential is the mechanical vibration. Initially, it may hardly be discernable; however, after some time it may increase significantly.

 

[CARF]

Hi all,

No the motor and pump are properly connected. It's a tri-lobe pump, worn out a bit. Reverse drive will mean reverse flow. Mechanical vibration is a good thing to look after carefully.

Thanks all,
MVD

 

[jbartos]

Suggestion to the original posting: It depends where the current is measured and by what kind of amperemeter. Please, where was that 5A measured?

 

[GusD]

Hello MVD

All motors, or I should say most motors; have an overspeed capability that takes in consideration bearings and mechanical/electrical motor design in consideration.THis over speed is around 10% or so.
You are talking about doubling the speed on this motor and notwithstanding the loss of Torque,which would be very large,you still have other problems to contend with.
An increase in speed such as that,should not be made without consultation with motor manufacturer.
I don't recall a time when we ran a motor to that deggree of Overspeed and that is probably true to most people.
Check with the Vendor and see what he says.

GusD

 

[CARF]

Hi all,

The current take up (Amperes) was measured through the Danfoss frequency drive. The thing can measure torque as well. Yes, I consulted the manufacturer (Eurodrive), see above.

Greetings,
MVD

 

[HawkBrazil]

Dears,

I saw only two problems:

1) What can be the bahavior of the fan, in case of a overspeed operation ? Furthermore, what's the type of fan used - Scirocco ? Limit Load ?

2)All rotating machines, electrical or not, have in a project a parameter called "CRITICAL SPEED". This speed rarely is under the nominal frequency of the mains,(but possible) and in this case one survey about this machine close to a manufacturer is highly recomended. In this particular case we are treating about overfrequency, and the survey must be made Everybody knows about the mecanical damages if we operate in a critical frequency (ies - yes, we can have more than one !!! ) for a long period.

Nice to type

 

[jbartos]

Suggestion: There have been posted max RPMs about 6000-7000RPM for induction motors 3600RPM. Apparently, the mechanical wibration, bearings, lubrication, stresses on the rotor cage, etc. may be limiting factors.