[DennisCNC]

I have a Perske spindle its 3 HP 17k RPM 8.1 Amp 300Hz. I put a 3 hp, 11 amp vfd to it and it just rotates very slow, does it need a more powerful vfd? If so what amps does it need, I looked on the perske site and didn't see any info about this?

Thanks

[Al_The_Man]

What frequency have you got the VFD set to?
Is the Perske the same voltage as the VFD out?
Al.

[DennisCNC]

The vfd is set to 300hz and its the same voltage as the spindle and I double checked the wiring.

I seems like the vfd doesn't have enough power to get it going faster.

[Al_The_Man]

By the label freqency and rpm it is a 2 pole motor, so if you set the output at 60hz it should turn at a little under 3600rpm, set for 60hz and measure the voltage output on each phase (across two phases) and see if the motor rpm has changed.
Al.

[DennisCNC]

I have another high RPM motor the I connected to the VFD and it does the same thing like the Perske spindle. The motor is 1hp, 220v, 400Hz, 5500rpm. The VFD just sits around 3-5Hz on the display with out going faster. Then I connected a regular 3hp squirrel cage motor to the VFD and it works fine, it accelerates to full speed.
It is one of these VFD's http://www.5bears.com/vfd.htm

What do these high Hz motors need? Does the VFD need to have a lot more amps than the motors need?

[Al_The_Man]

How are you controlling the speed? The thing I do not understand is that if you set the VFD for 60hz, why is it showing 3-5Hz on the display?
As long as there is not a fault detected, the output frequency should be whatever you set it to?
Al.

[DennisCNC]

I don't know know why it's not going faster then ~5Hz also, I'm controlling the speed with the pot on the VFD, the vfd doesn't fault or over current. With the squirrel cage motor it gets up to speed in no time but with the two other high rpm motors doesn't want to. Maybe it doesn't like them?

[Al_The_Man]

Does the VFD have Keyboard entry for frequency? IOW instead of external, use local enter the speed (freq) and start?
Al.