460V/60Hz rating vs 400V/50Hz rating of a motor

[voltages]

We order a 460V, 60Hz specs squirrel cage motor (12/7KW) at dual speed 1445/730 rpm. But the supplier delivers us instead of 400V, 50Hz (same KW, n rpm rating)motor.

The supplier explains that the 400V, 50Hz is just the equivalent of 460V, 60Hz rating.

Is it really safe to operate this motor at power supply of 460V and at 60Hz frequency, any advice. thanks.

 

[jraef]

Pretty close. Motors produce torque based upon their V/hz ratio. 460V 60Hz is a 7.6:1 V/Hz ratio. 400V 50Hz is 8:1, so it is close, usually considered close enough (technically a 380V 50Hz motor would be exactly the same, but in many areas 400V has replaced 380V anyway).

BUT:

1445 is an RPM associated with a 4 pole 50Hz motor with a 3% slip. If you apply 60Hz to it it will spin at 1800RPM synch., 1746RPM slip. At that higher speed and the same torque, the motor shaft power will be higher, i.e. 14.4kW. This usually isn't much of a problem but mechanically, you want to make sure the components will not be damaged or that if it is on a centrifugal load the higher speed doesn't translate to requiring even more power than this. If so, or if the 1455RPM is critical, you may want to consider a VFD.

 

[dpc]

Check this out:

faq237-1224

 

[edison123]

Voltages

You said

"We order a 460V, 60Hz specs squirrel cage motor (12/7KW) at dual speed 1445/730 rpm."[/color red]

1445/730 RPM at 60 Hz ? It should be around 1750/875 RPM at 60 Hz.

Something wrong here. Could you please check up ?

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[waross]

What edison123 said.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

Cool. My final conquest of TGML codes gets an approval.

Thanks Bill.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[jraef]

Yes, well done. I guess my prior response which pointed out the same thing didn't get attention because of my lack of TGML coding. [!]Lesson learned.[/!]

 

[edison123]

jeff

Are we seeing red[/color red] or green[/color green] here ? LOL.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[waross]

Sorry jraef.
As soon as I posted, I thought
"And what jraef said also".
Sincerly

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

I'm not serious about being miffed... that's why I put in the "wink". I have more PLS's than I can possibly use for the rest of my life.

 

[edison123]

I know Jeff. Did you miss my LOL ?

I was just showing off my "colorful" personality...

"wink, wink". (I haven't mastered the smileys yet)

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[roydm]

Edison123,
I'm so sick of reading that quote, can you change it now and then.
Kind regards

Roy

 

[edison123]

Hey Roy,

Umm... Let me see, how I can improve my "signature".

If I removed "Chris Rock", would that make you happy ?

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[roydm]

Edison123,
No, it's the "women are like police----" quote. Every time i see it, even though I know what it says I can't resist reading it again.
I guess that's my problem, not yours.
Cheers
Roy