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Motorcontrol

Hello group,

I am trying to build a motorcontroller for a 24V 50W DC motor. Maximum operating current is 8 amps, when the motor is loaded. My plan is to rectify a 24VAC and feed it to the motor directly and then control its speed by PWM'ing a mosfet. The manufacturer says it is OK to use the higher voltage on the motor. I continously monitor the motor and adjust the speed to my desired value, regardless of the load.

But I am wondering: What amount of capacity do I need on this rectified voltage? Is ripple a problem for my motor, with 8 amps there is quite alot.

Thanking you in advance.

Henrik

Reply to
Henrik [6650]
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Zero.

No. It will average the voltage quite nicely.

By the way, a 28 volt motor that draws 8 amps is using 224 watts, not 50.

Reply to
John Popelish

With straight rectification of the AC PWM'd into the motor there will be significant ripple current. Your motor will dissipate more heat for the average torque available -- but unless you're pushing it really hard it should be OK.

If you need information on control related stuff see my website.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

I have successfully used a series inductor to smooth the current in rectified phase controlled DC motor applications.

Reply to
John Popelish

Oh yes, The 24V 50W is nominal, the 8 amps is maximum according to the motors torgue table for maintaining the desired torgue at a given load.

Thank you both for your answers.

Henrik

Reply to
Henrik [6650]

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