RE: [CAD_CAM_EDM_DRO] PWM vs. DAC?

He's not wrong. A DAC to an analogue amplifier dissipates large amounts
of energy across the drive transistors whereas the PWM only during the
switching time.

Think of it this way. Drive voltage is 100V drawing 10A (1000W) and the
motor turns 1000 RPM. To turn 500RPM you need to drop 50V across the
motor and 50V across the drive transistors at now 5A.

That's 250W of heat the linear amp has to get rid of. Or, 100% duty
cycle of 100V puts 10A into the motor for 1000 RPM while 50% duty cycle
averages out to 5A and 50V for 500 RPM.

This is a gross simplification but will give you an idea.

John Dammeyer


Automation Artisans Inc.
http://www.autoartisans.com
Ph. 1 250 544 4950

> [maxnc15]I've hired an electronics man in Russia to produce an S-Curve
> controller for a hydraulic robot project. He says PWM (Pulse Width
> Modulation) is much more efficient than DAC (Digital to
> Analog Control)
> [Aaron] Perhaps he is using PWM plus some filtering to make a
> poor man's
> DAC?
>
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