RE: brushless servo drive?

Bill asks:
-----------------------------------------
From: "Wm McNett" <wmmcnett@...>
Subject: brushless servo drive?

>What is needed to control a brushless servo?
>Brands?
>Gecko says "brush".


>Thanks,
>Bill

Bill,

Brushless servos are very similar to a three phase
induction motor and require a brushless drive. The
motors you specified can be driven by most drives that
will take either a hall input or hall/encoder inputs.
The difference will be how much torque ripple you get.
You'll note these take a fairly high voltage. Going
with lower voltage will lower the top speed, probably
not a big concern.

Unfortunately, it takes some research to get the
correct drive. You particularly have to pay attention
to the resolution of the encoder. Some drives will
only use one encoder resolution. Tons of companies
make drives that will work, but the prices are high
new, think $500 per axis and up. There are lots of
drives that only use resolvers, you don't want those.

Rutex may be your best bet, but I have no experience
with their drives. www.rutex.com

Ebay perspective:

API makes nice drives, but they charge $500 for the
setup software. Pacific Scientific also sells
rebranded API and their own drives which might work.

AMC makes flexible drives, but it takes some
engineering to use them. They tend to be lower
voltage.

A lot of Compumotor drives only work with one specific
type of motor. They bought MTS's servo systems
division recently. MTS makes some drives that would
work.

Electrocraft has some nice drives, also sold by AB and
others.

Yaskawa might work, haven't looked into it.

I recently looked into World Servo, they may be the
best choice if you have to buy retail.

Texas Instruments, Microchip, Freescale Semiconductor,
and Analog devices all sell DSP/Microcontrollers that
are specifically intended to drive brushless servo
motors. Freescale has some nice application notes.

As I said, there are tons of companies in this
business. I particularly recommend that you obtain
the documentation before you buy and make sure it will
work with the motors you have and your desired control
method. Otherwise you'll end up drowning in drives.

Eric






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