# Ideas for Bench Testing an AC motor



## DBens (Apr 28, 2011)

Hey everyone,

I'm looking to bench test an AC motor, specifically an AC-20 with curtis 1238 controller.

I'll have access to a variable DC power source. And I was wondering what types of tests/ what kind of data I can collect from running the AC-20 with no load.

I was hoping to get some concrete data down, something other than just watching it spin.

In the future I may be able to get to a dyno, in which case I can look at current/voltage, power in and power out etc. 

But are there any other ideas for bench testing with or without a dyno?

Thanks


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## frodus (Apr 12, 2008)

max RPM really

without some sort of load, not really much you can get. Maybe put a fan blade on it and load it some and run it for an hour or two and monitor temperature.....

without a dyno or some sort of measurable load, not sure you can get anything really useful (torque, HP, efficiency).


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## Salty9 (Jul 13, 2009)

How about using the AC20 to spin another motor used as a generator. The output of the generator could be run through resistances such as water heater elements. I'm not sure about the kind of motor to use as a generator.

Alternator dyno from Endless Sphere:

http://endless-sphere.com/forums/viewtopic.php?f=30&t=24850&p=358976&hilit=dyno#p358976

The alternator probably doesn't have the capacity to fully test the AC20.


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## major (Apr 4, 2008)

DBens said:


> I was hoping to get some concrete data down, something other than just watching it spin.


Hi DB,

Without some way to load the motor, you cannot get any meaningful data from such testing. Although I do recommend you do it. It does provide you with experience with the system. Both in the wiring and in the use of the handheld device. This will save you time and headaches when you install it on the vehicle.

I recently had the opportunity to have two AC15 systems on my bench at the same time. For the cost of an appropriate coupling, I was able to hook them shaft to shaft. And then DC inputs together along with a battery. By doing this, I could run one motor as a generator and load the other motor. You do not get an actual torque readout, but you can back figure torque pretty closely. This worked pretty well and I could load the motor to the max with only about 1/4th the current coming from the battery.

It was just getting interesting and I had to deliver one of them to the client. Anyway, food for thought if you could get a second system. Other than that, load devices for bench testing at these speeds and powers are difficult to come by. DC generators, AC motors with inverters, hydraulic pumps, water brakes and maybe fans come to mind as possible load devices. Inertia (flywheels) also work as loads, but just for transient periods, so you have to be fast to collect the data 

Good luck,

major


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## GerhardRP (Nov 17, 2009)

Sounds like a combined motoring/generating efficiency of 75%. If the losses are equal, you get 87% for each. Did you separately measure power in/out for each controller? 
Gerhard


major said:


> <snip> I recently had the opportunity to have two AC15 systems on my bench at the same time. For the cost of an appropriate coupling, I was able to hook them shaft to shaft. And then DC inputs together along with a battery. By doing this, I could run one motor as a generator and load the other motor. You do not get an actual torque readout, but you can back figure torque pretty closely. This worked pretty well and I could load the motor to the max with only about 1/4th the current coming from the battery.
> 
> major


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## major (Apr 4, 2008)

GerhardRP said:


> Sounds like a combined motoring/generating efficiency of 75%. If the losses are equal, you get 87% for each. Did you separately measure power in/out for each controller?


Hi Ger,

We were not doing efficiency tests. Had other issues at hand. And when I said 1/4th, it may have been 1/3rd. It was a pretty rushed situation and is why I am reluctant to post any data. Just that the method works very well for motor testing. I've done it before. When you can get your hands on a matched pair of motor/controllers, try it 

Regards,

major


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