question about testing a motor .

[bluntstar]

Greetings, I'm new here and have a couple of questions.  I figured I should post here because I didn't want to annoy anybody by posting in the wrong section etc.,

I got a motor that has no specs written on it , I was told however that it's a 72V ametek dc motor , with 1750 r.p.m at 72V dc .   The length of the shaft, size and diameter of the motor as well as weight are same as the ametek 72V except that this motor is black in color not green. therefore I am not sure as no specs are written on it.

Q1
As I'm not completely sure about these specs , how would I go about running tests on this motor to find out what it can do for me ?
I hooked it up to a multimeter and with just a spin of the shaft with my hand I get results out of it .

Q2
Another question when I have the multimeter set to D.C.v  the shaft can be spun with my fingers with not too much problem ,  but when I switch the multimeter to D.C. amp  the shaft becomes very hard to spin (lots of resistance)  is this normal? 

Could anybody answer these 2 questions for me.  THanx . 

[Madscientist267]

A1 -

    Start small; if it's a PM motor, it should run on a wide range of voltages, provided the shaft remains unloaded.

    12VDC (from a car battery) will give you an idea of if it is close to being as described. The shaft should spin fairly slow, with rather limited torque at that voltage.

    If you're then reasonably sure that it is what you think it is, you can use a variac through a bridge to bring it up (slowly!) to 72VDC to find out more (fuse it at a reasonable current!).

    I had an 80VDC motor once that I knew little else about, tested it in much the same way.

A2 -

    Yes. Normal. Indicates both the motor is functional, and the fuse in your ammeter isn't blown.

Steve

[zap]

If you're thinking about using the motor for a wind genny then knowing the volts per RPM can come in handy.

[Norm]

A pulley with a handcrank on it such as bicycle ....count the teeth...a chain wrapped around a
wooden pulley that has a fifth as many links as the sprocket teeth engaged to it.
Now 1 turn per second will turn the motor at 300 rpm. Should give you about 12 volts.
divide 1750 by 72 x 12=rpm for 12 volts open voltage.
Norm

[bluntstar]

Great , thank you guys for the help   
can't wait to get to work on it, and that includes reading through these vaults of information.
THis place is great
THNX

[wooferhound]

Welcome to the forum
We love to have new people around to influence them to spend their money on making power for themselfs