RE: [CAD_CAM_EDM_DRO] Re: Servo motor HP for Bridgeport

Ian:

If you use an "old" style driver which puts a large resistor in series with
the power supply and motor winding, the voltage drop across the motor can
become negligible if it is small, compared to the voltage drop across the
resistor, and the power drive approximates a constant current drive.

If you use a "new" style chopper driver, then you're actively "measuring"
the current and controlling it to a "specified" value, again approximating a
constant current source.

I looked at the Oatley web site. It appears that they're varying the coil
voltage to keep the motor current constant. This will also work, as long as
the open circuit voltage of the power supply is not higher than the voltage
that the switching transistors can withstand.

-- Jerry

| -----Original Message-----
| From: sutherland_oz@... [mailto:sutherland_oz@...]
| Sent: Saturday, August 25, 2001 9:54 AM
| To: CAD_CAM_EDM_DRO@yahoogroups.com
| Subject: [CAD_CAM_EDM_DRO] Re: Servo motor HP for Bridgeport
|
|
| Hi all, message #29580 refers to chopper drives being the stepper
| answer, but an Oz firm Oatley Electronics,
| http://www.oatleyelectronics.com/ says that the answer is to use a
| constant current source, (kit #K142C) I'm about to build a small CNC
| mill for home use & would appreciate any comments, Ian S.
|
|
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