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### Author Topic: max power from vfd  (Read 2322 times)

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#### comet

• 318
##### max power from vfd
« on: April 01, 2012, 10:41:28 AM »
Hi,
if you have a 3 phase motor running off an inverter,what frequency is the maximium torque generated at?
for example i have a 3 phase 230v motor rated 2800 at 50hrtz.
is max torque at 100% 50hrtz or at 80% (40 hrtz) ?

#### HimyKabibble

• 1,687
##### Re: max power from vfd
« Reply #1 on: April 01, 2012, 10:53:23 AM »
A 3-phase motor driven by a VFD will have constant torque up to the motors base speed, and constant power above base speed.

Regards,
Ray L.
Regards,
Ray L.

#### comet

• 318
##### Re: max power from vfd
« Reply #2 on: April 01, 2012, 11:02:29 AM »
ok,so what does that mean in the real world?
I know that when you over or under frequency the motor it loses power/torque is it like a dc motor that at poroduces the most power at 80% rated rpm

#### HimyKabibble

• 1,687
##### Re: max power from vfd
« Reply #3 on: April 01, 2012, 11:10:19 AM »
It produces the same torque at any speed below its base speed, which means power below base speed falls off with RPM.  Above base speed, power is constant, which means torque falls off as speed increases.  So, you'll have full torque at any frequency up to 50Hz, and decreasing torque above that speed.  At 100 Hz, torque will be half what it is at 50Hz.  If it's a 1HP motor, it will deliver 1 HP at 50Hz and above, but only 1/2 HP at 25Hz.

Regards,
Ray L.
Regards,
Ray L.

#### comet

• 318
##### Re: max power from vfd
« Reply #4 on: April 01, 2012, 11:17:11 AM »
right, so I will be able to use the highest feed rate with the spindle motor running at its design frequency,50hrtz.

#### HimyKabibble

• 1,687
##### Re: max power from vfd
« Reply #5 on: April 01, 2012, 11:41:05 AM »
Not necessarily.  If you're torque or power limited, then perhaps.  But with smaller tool, very likely higher RPM will allow higher feedrates, but you won't be torque or power limited.

Regards,
Ray L.
Regards,
Ray L.