# Seperate motor for other stuff



## evmetro (Apr 9, 2012)

I have been trying to find a motor to run the air conditioner, 140 amp alternator, and power steering pump. The drive motor that I am using does not have a tail shaft. I am running a 153 volt pack, and wish to have a separate motor to run the accessory pumps all the time. When I search for dc motors, the smaller ones seem to all be lower voltage, and I can't find any that would be right for 153 volts. I am having the same problem when I search for small high voltage controllers. Does anybody know of an appropriate motor that could handle this task that would work at 153 volts? Would it be possible to have it start up and run at a fixed rpm or fixed number of watts without running a controller? I was also thinking that it would be nice to be able to shut this motor down for a "range emergency"...


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## evmetro (Apr 9, 2012)

From what I calculate, I should need 2 hp for 5000 btu's of air conditioning, 2hp for the power steering, and another 2 hp to get 100 amps out of the 140 amp alternator. 6 hp total. 4470 watts. It would appear that the motor that I can't seem to find would run on 153 volts DC, at 30 amps... From what I can tell from my surfing session, this motor does not look too realistic. I feel like I am missing something, since everything I find looks big enough to use as an EV drive motor. Maybe I am way off for my power requirements estimate?


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## dougingraham (Jul 26, 2011)

EVMETRO,

A motors RPM is controlled by the voltage and the load determines how much current it pulls. You will probably need some kind of motor control to spin it at a desired RPM. I think you might be better off using a DC-DC converter instead of the alternator, an electric power steering pump, and an electric AC compressor like the master flux unit for the AC. You get a lot more choice in placement if you separate these devices.


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## Tesseract (Sep 27, 2008)

evmetro said:


> From what I calculate, I should need 2 hp for 5000 btu's of air conditioning, 2hp for the power steering, and another 2 hp to get 100 amps out of the 140 amp alternator...


A modern window unit A/C needs ~500W for 5000 BTU; car A/C systems can use 3500W or more of power, but they usually deliver more heat transfer than 5000 BTU as well. IIRC, 12000 BTU is typical for a medium size car (ie - not a Geo Metro, but not a Ford Expedition, either).

The typical car alternator with a claw pole rotor, however, is notoriously inefficient: usually around 55%. In other words, you could need 3500W to drive that 140A alternator.

Your estimate of 2hp (~1500W) for power steering seems reasonable.

As for what kind of DC motor to drive all three loads, a PM or shunt wound type would be best because either will maintain a fairly constant speed despite varying torque loads. While a series wound motor could be used, it would need a speed controller.



dougingraham said:


> ...I think you might be better off using a DC-DC converter instead of the alternator, an electric power steering pump, and an electric AC compressor like the master flux unit for the AC. You get a lot more choice in placement if you separate these devices.


I don't disagree with your recommendations, per se, but I will note that alternators are far more reliable than the usual AC/DC switching power supply that is press-ganged into use on EVs. Also, the electric power steering systems made by Mazda, Toyota, etc. are much more efficient than the engine-driven pump type. I reserve judgement on the MasterFlux system, but only because the only experience I have with it is from tech support inquiries about their input capacitors blowing up. Apparently MasterFlux thinks traction batteries always deliver pure DC and never sag...


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## evmetro (Apr 9, 2012)

Thanks for the replies. I am wanting a big 12 volt system on this ride for lots of luxuries and a big sound system. Lots of DC DC converter costs lots of money, and I have the cs144 140 amp alternator that came out of this rig, so it would be nice to use it. I am reading up on electrifying the individual components, but it would sure be fun to run them off of an accessory motor.


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