9 replies to this topic

[porky]

Driving a Cryogenic pump motor, the motor rating plate states that the Nominal Voltage is 400V, 6090 RPM and 101,5 Hz.

It also states that the motor may run between 62 and 110 Hz with a speed of 3700 to . I think 6900 Rpm... not too sure on the actual value.

I programmed the nominal rated frequency and RPM into the drive and the motor just kept on shuting down within seconds of starting .... the only fault it indicated was overbraking..... Im lost... since over braking should not apply at start up...
I played around with the settings and set the rated motor frequency at 62 Hz and the RPM at 3700 .....and it works well no problems at all....

I am still confused as to why it would not work with the correct name plate settings. Can anyone shed some light...

[mariomaggi]

Dear porky,
the unit must work, but we have not enough data to give you the right suggestion.
Maximum theoretical speed will be 6600 RPM at 110 Hz

Asyncron motor or synchron motor? From the nameplate (6090/101.5 = 60.0000) it seems to be a synchron type).

New installed unit or old unit?
Inverter manufacturer and type?
Supply voltage?
Setting of acceleration ramp time?

Regards
Mario

[porky]

Dear porky,
the unit must work, but we have not enough data to give you the right suggestion.
Maximum theoretical speed will be 6600 RPM at 110 Hz

Asyncron motor or synchron motor? From the nameplate (6090/101.5 = 60.0000) it seems to be a synchron type. it is a sycron motor

New installed unit or old unit? Brand new
manufacturer and type? Altivar61
Supply voltage? 400Vac
Setting of acceleration ramp time? 8 seconds, but I did try several different times but still had the same result
Regards


Regards
Mario

[porky]

hi

Just a querry, with respect to my previous question,
From the attachment what would you put as the nominal speed and frequency and voltage in the program?
and what is meant my weakening frequency ?

Many thanks
Paul

Attached Files

•  SEFCO.pdf   162.57KB   33 downloads

[jraef]

First off, in the VFD, speed is only relevant in the way the drive displays the operating speed. The motor parameters are set up by the voltage and frequency.

From what I see on that nameplate, I would say that this motor is rated for 110Hz at 400V, but that seems to contradict what you have experienced. The field weakening point is confusing though. Usually the field weakening point is just above the synchronous speed, because at that point you have no more voltage to give to the motor so you begin operating in a constant power mode, losing torque as you increase frequency above that point. If that were the case then, that would make me think the design frequency of the motor was 100Hz then.

It could be that this nameplate is really denoting the operating range of the entire pump as a unit, not the specifics you need for programming the VFD. It is saying that although the pump can be operated between 62 and 110Hz, once you go over 101.5Hz you will be losing torque. If on the other hand it was in fact a 62Hz designed motor as your experiment seems to indicate, then your Field Weakening point would be around 62.5Hz and by the time you got to 110Hz you would have very little torque left in that motor.

Now I am as confused as you.

Sorry.

I think this is a question to be discussed with the motor or the pump manufacturer if possible. That is a very non-standard nameplate to my experience.

[AB2005]

I think this is a question to be discussed with the motor or the pump manufacturer if possible. That is a very non-standard nameplate to my experience.

I agree with Mr. Jreaf. This is very strange Name plate, f range = 62-110HZ and field weakening point = 101.5HZ.

[kens]

Hi Porky, as stated earlier that seems to be a pretty unique nameplate. Out of interest i had a look at their website but i found it short on tech info and long on large glossy brochures. Try the link below for their service department and they should be able to help.

http://www.sefco.ch/...ntactsform2.htm

Ken

[mariomaggi]

porky,
you don't supplied enough data, the motor is not identified (100 W? 30 kW?)
Also the inverter size is not known.

One possibility is the wrong coupling between such synchron motor and such drive. Don't forget that Altivar 61 has a limited possibility to supply current, being a HVAC inverter.

Regards
Mario

[porky]

porky,
you don't supplied enough data, the motor is not identified (100 W? 30 kW?)
Also the inverter size is not known.

One possibility is the wrong coupling between such synchron motor and such drive. Don't forget that Altivar 61 has a limited possibility to supply current, being a HVAC inverter.

Regards
Mario

............Take a look at the attachment that I placed on my second posting ...it has all the information tha you requested.

[marke]

Hello Porky

Firstly, if the motor is a synchronous motor with a permanent magnet rotor, you may need to alter the drive settings to suit. Some drives are designed to operate with induction motors only, others are designed to operate with induction motors, and permanent magnet motors. There will be a parameter that need to be set for this.

With an inductive component, in order to maintain a constant flux in the iron, we use a constant V/Hz ratio.
Below the nominal frequency, we reduce the voltage with the frequency such that the ratio of V/Hz is the same as at the rated voltage and frequency.
As we increase the frequency above the rated frequency, we can not increase the voltage because it is limited by the input voltage. This results in a reducing flux at higher frequencies. This can be known as field weakening, but this is usually applied to DC motors rather than induction motors.

I would suggest that you set the rated frequency as equal to the field weakening frequency and the rated voltage at 400Hz.

Best regards,