# accessory motors



## evmetro (Apr 9, 2012)

I am not super educated in motor principles, but I am trying to find a dc motor (s) to run factory belt driven accessories; ps, pb, alt, ac, etc. I was hoping to get some guidelines for how to choose a dc motor that can work with 150 volts and not work too hard or be overkill...


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## onegreenev (May 18, 2012)

What are you planning on running with your dc motors? 

Pete


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## Woodsmith (Jun 5, 2008)

Would a shunt motor work?

A shunt motor would run at the same speed even when the loads change, by drawing more current, and won't over speed if the load suddenly disappears if the belt breaks. You can then choose pulleys that will give the most useful speed for each of the accessories.

I am just wondering is a forklift pump motor would be shunt wound. Major would know about these things.


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## TEV (Nov 25, 2011)

Hi, in my conversion I kept the original components of the A/C system and use a separate AC industrial 5HP controller to drive the compressor using an AC industrial 3 phase motor. The first motor I got was only 3HP (I paid only $50 for it) and I was sure that will have enough power, unfortunate after a few minutes of runing the 3HP motor will stall, I upgraded to a 5HP motor (the controller was a 5HP already)and everything is fine now.

Consider this a warning that you may need to try a few motors until you find the right one, also you may have to use a motor controller for the accessory motor even if you use a DC motor.


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## evmetro (Apr 9, 2012)

I have been surfing the web looking for motors that run with 150vdc, but it looks like they jump from 90vdc to 180 vdc. Anybody know where to source an accessory motor that will work with 150?


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## major (Apr 4, 2008)

evmetro said:


> I have been surfing the web looking for motors that run with 150vdc, but it looks like they jump from 90vdc to 180 vdc. Anybody know where to source an accessory motor that will work with 150?


For industrial or appliance motors, 90 and 180 VDC seem to be the standards. There is nothing wrong with running one of those motors at 150 VDC, depending on the type of motor. You'd just have to plan for the difference in RPM, HP, rating, cooling, etc. Or use the 90V motor with an appropriate speed controller which limits the motor voltage.


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## evmetro (Apr 9, 2012)

Major, I was hoping you would stop by this thread... thanks. If I went with the 180vdc, would it be ok to just start and stop it with a contactor? I read something that teseract wrote recently about an ac compressor using a 1 to 3 kw motor...if I wanted a 3kw motor, it looks like I could divide 3000 watts by 150 vdc for 20 amps rating. When I look at 180 vdc motors, they seem to be rated in hp. Do you have any recommendations for what specs I should look for for an air conditioner drive motor for ac compressor?


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## major (Apr 4, 2008)

evmetro said:


> If I went with the 180vdc, would it be ok to just start and stop it with a contactor?


Your contactor will arc on opening. A freewheeling diode might resolve that. But the motor will draw stall current on start-up for a short period and will arc on the comm. How badly and long it will last is unknown.



> I read something that teseract wrote recently about an ac compressor using a 1 to 3 kw motor...if I wanted a 3kw motor, it looks like I could divide 3000 watts by 150 vdc for 20 amps rating. When I look at 180 vdc motors, they seem to be rated in hp.


1 HP = 746 Watts.



> Do you have any recommendations for what specs I should look for for an air conditioner drive motor for ac compressor?


Typically AC = alternating current and A/C = air conditioning. It'd be nice to use AC for A/C  Then you could use a sealed compressor/motor unit. But 150 VDC ain't going to get it for a 230 VAC A/C compressor. And 150 VDC to 120 VAC converters ain't too common. So you're left belt driving a compressor with a DC motor and that sucks. 

Good luck.

major


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## evmetro (Apr 9, 2012)

The A/C and AC lesson and the hp lesson where VERY helpful. Those will both stick. I suppose the DC motor that I end up using will not be under a really heavy load upon startup, since there is a clutch on the A/C compressor. I was thinking about removing the A/C clutch to save weight and energy, but not if the motor will take a beating.


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## onegreenev (May 18, 2012)

Why not just drive the AC off the accessory shaft if you happen to have one. Since you'd be using the compressor clutch I don't think it would draw that much excess power to freewheel the pulley vs having to integrate a whole motor and controller just to drive the AC compressor.


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## major (Apr 4, 2008)

evmetro said:


> I suppose the DC motor that I end up using will not be under a really heavy load upon startup, since there is a clutch on the A/C compressor.


The magnitude of the start up current upon contact closure is independent of motor load. The duration of that high current is dependent on how fast the motor accelerates up to speed, so is sensitive to the inertial load on the shaft. Lastly it is affected by the load itself, the compressor, or friction.



> I was thinking about removing the A/C clutch to save weight and energy, but not if the motor will take a beating.


For motor life, smoothness, noise and efficiency it would be best to use a variable speed drive on the motor. This would eliminate the need for a clutch, limit the inrush current spike, and could improve the control. Use variable speed to control flow as opposed to fixed flow on/off modulation. This also allows you to use the full capability of a 90V motor on a 150V system. Just limit the motor voltage with the variable speed controller.

We did this with a 100hp compressor at the ice arena. It was unbelievable the improvement from a variable speed drive. Same idea, smaller scale


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## onegreenev (May 18, 2012)

What type of variable speed controller are you thinking about? I was thinking of a small sepex motor with a pwm controller and a dash mounted throttle to position what ever you need. Turn it off and at the off position you have a tab that contacts a micro switch to shut off the contactor under no load conditions.


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