Is a filter needed for ironless motors?

[pixpop]

The machine I'm designing will use an ironless linear motor for one axis, and an ironless DC servo (pancake motor) for the other axis.

I see on the GD website that the drives are 'compatible' with these motors.

When using GD drives with ironless or low inductance motors, is it necessary to install a low pass filter to protect the motor?

(On another project, I was using Gecko drives, and they required the installation of an LPF when used with low inductance motors.)

Thanks,

Neil

[pixpop]

More info, in case it's helpful, inductance figures:

The Linear motor quotes 4.8 mH phase to phase.

The pancake motor quotes armature inductance as < 100 uH

So I'm guessing the Linear would be OK, but not sure about the pancake.

[pixpop]

Duplicate message

[H.O]

Hi,
It depends on the motor supply voltage. Looking at the datasheet for the 160V version of the VSD-E it states a minimum motor inductance of 0.005mH/V so the linear motor shouldn't be a problem at all.

If the inductance of the pancake motor is 100uH max operating voltage would be 20V.

Tero will have to fill in the details about the design of an external filter for the pancake motor, if possible.

[Xerxes]

H.O is correct about voltage vs minimum inductance relation.

To make low inductance motor compatible, one should connect inductors in series with motor windings. Inductors should be large enough to fulfill the minimum inductance specification of drive and current rating of motor. Also a RC snubber may be a good idea connected to motor terminals to reduce voltage peaking after inductors.

Some commercially available motor filters:
http://copleycontrols.com/Motion/pdf/FL1.pdf
http://copleycontrols.com/Motion/pdf/Xenus-Filter.pdf