Re: [CAD_CAM_EDM_DRO] Need help with Dyno design

Wally, Wouldn't it be easier to turn a 2"long X 2.125 dia spool in the lathe with a 16 tpi groove on its diameter. Mount spool on motor shaft, wind a cable on the spool with different weights suspended from it? Steel is .282 pounds per cubic inch to calculate the standards. Run different Rpm's and distances to see where it skips. Could run that Eckstein's DRO system with an encoder mounted on shaft to verify. Or a simple reference mark from shaft to motor body.

Ron

cnc_4_me <cnc4me@...> wrote:


I could use some advice on using multiple motors in parallel for a
dynamometer load.

I want to build a dyno to give me the torque curve for some powerful
steppers I have. The problem I am having is the steppers have so
much low end torque it will take a minimum of 3 treadmill motors for
a load, and I may build the dyno to use 5 load motors.
The stepper has a running torque of 1208 oz-in and each treadmill
motor has a maximum torque of 441 oz-in (2.25Hp at 5100RPM 260Vdc 5A).
The load motors would be connected to each other with 1-1 gears.

To control the torque of each motor I was going to use Masiss��s
dynamometer circuit. It can be found here.

In the CAD_CAM_EDM_DRO file section
Files��circuits�X>miscellaneous ,circuits��dynomometer circuit.pdf

http://f5.grp.yahoofs.com/v1/IA4XQimTsSyrH7uH0OGaenRM5_adVog79qfEKuhBP
LkLJoZbQOwXh_oohX_HoZciVSJjDU3Y9WBBAQn4vCZL1JcOSV-
Y/CIRCUITS/Miscellaneous%20Circuits/dynomometer%20circuit.pdf

This circuit uses an op amp to control a few power FET��s to slowly
energize the load motor.

I am thinking that each motor would have to have its own power FET
control circuit in order to balance the load. I am also thinking I
need 1 POT to control all motors and each power FET circuit should
track together.

With that said I am unsure if this circuit will do that. I think the
control POT could be P1 in the schematic and all op amp power FET
circuits would connect to this point. Then P2 could be used to match
the loads. While that sounds good in theory I do not know how well
these circuits will keep the motor current in sync.

Does anyone have any advice?


Wally






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