Re: [CAD_CAM_EDM_DRO] Unknown servo motors...

On Thu, 11 Sep 2003 00:43:21 -0500, you wrote:

>
>
>Harvey White wrote:
>
>>OK, I have some Minertia servo motors, and the specifications seem
>>rather hard to get...
>>
>>Is there a reasonable procedure to go about to determine the motor
>>characteristics? If so, where would it be documented?
>>
>>
>There are two numbers that can be obtained from the motor with relatively
>simple measurements. They are related, so you only need to measure
>one. If you have a mill or lathe with well-known spindle speeds, chuck
>the motor to the spindle, and run it at around 1000 RPM. Measure the
>DC voltage generated by the motor. Correct for the whatever spindle
>speed you are getting, and you have the Kv constant. this is normally
>expressed as Volts/1000 RPM. So, if you have 1200 RPM, take the
>voltage/1.2 and you have Kv. Multiply Kv * 1.351 and you have
>Kt, the torque constant, in Oz-In/Amp units. If Kt was 45 V/1000 RPM,
>then Kt must be 45 * 1.351 ~= 70 Oz-In/Amp.

Thanks. I have that information, at last, on these minertia
motors... Not that it was easy to get. I will remember this for new
(and unknown) motors.

Harvey

>
>The hardest numbers to get are continuous torque and peak current.
>If you exceed the continuous torque rating the motor will overheat
>and eventually break down the winding insulation. If you exceed
>the peak current, even for an instant, you can demagnetize the
>magnets, altering the Kv and Kt constants, usually much for the worse!
>
>The continuous torque ratings can usually be guessed at by comparing the
>motor to others of similar size and construction. If the motors run cool
>all the time, you probably don't have much to worry about.
>
>The peak current is often in the range of 2 - 4 X the current equivalent
>to the continuous rated torque.
>
>Jon
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