Powering a DC motor with AC

[jeepman182]

What would you suggest as the most cost effective and space efficient way to run a 24v 10amp dc motor with 110v AC. Must be as portable as a cord will allow. An 8lb transformer with bridge rectifier isn't feasible, any other words of wisdom.

 

[MikeHalloran]

Speaking as a >>mechanical<< engineer who is known to be dangerous with electronics:

1. A single SCR with a gate control that turns on pretty late in a cycle, limiting the applied voltage. You'd probably need an 8 lb flywheel to integrate the choppy torque, and you'd never get near rated torque, but it would 'run'.

2. A high frequency switching supply with 24VDC/10A output.

3. Do you really need full voltage and full current? Switchers get smaller and lighter if you don't need both. You didn't specify a load on the mechanical side.

Did you need variable speed? That costs extra.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[jeepman182]

Voltage is required but current is variable, the load is variable, under full load 10amps is needed but it would infrequently be under the full load. Variable speed is required. Currently being powered by a 2.4a/h 24v battery with all the controls to run variable. I want to on occasion connect some form of converting apparatus to the unit to power it with AC. Unit will run with 24v 2amp transformer but not near its rated speed and power. Manufacturer of unit is unable to tell me the current of the motor (and short of doing a copmplete teardown) I had to estimate current draw by the time it takes at full load to drain the battery (about 15mins). Maybe I've estimated wrong. I barely know enough to be dangerous with this stuff. Any one with wisdom?

 

[eemotor]

As MikeHalloran mentioned, a 24 volt 10 amp switching power supply might do the job. They're light and small (probably around 1 to 2 pounds) and not very expensive either.

 

[bklauba]

Another option is to use a PWM drive from Minarik, like their model XL3200A. This is an open chassis drive, physical size is about 130 mm sq X 50 mm. Max DCA out is 10, and this unit features current limiting, 100:1 speed range control, and adjustable min spd, max spd, acc, &decel. Weight is less than 1 lb.

 

[jeepman182]

Thanks,

Any switching power supply's I've come accross are rated in watts and one of this size is from $300-$1000. Am I barking up the wrong tree?

 

[bklauba]

The Minarik would run you about $ 200, and it was specifically designed to run motors, hence the various motor speed function adjustments. (One that I forgot to list was IR compensation, which minimizes spd variations with variations in load).

You can control the speed by using a separate single 5K turn pot (one comes with it) or an isolated 0 - 10 VDC signal.

 

[bklauba]

Take a look at Minarik Electric's website:

http://www.minarikcorp.com/300ACDCdrives.html

Unfortunately, you can't access the specific model, but the series is shown, along with locations you can call.

I have used these drives on 1/2 HP, 50 VDC motors, and found them to work quite well.

BK

 

[jraef]

KB Electronics are the leader in low cost DC controllers like that. You can get a really inexpensive chasis unit for well under $100. Just saw one on EBay for $40.

http://www.kbelectronics.com/catalog_chassis.htm

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