Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: machmanchuck on May 01, 2010, 03:35:45 PM

Title: Using Sepex DC motors
Post by: machmanchuck on May 01, 2010, 03:35:45 PM

Hi everyone.

I have a pair of separately excited (non-permenant magnet) wheel chair motors from a Damaco (sp?) wheel chair motors.  I plan using these motors to power reel mowers for my R/C lawnmower.  I have searched everwhere I could find and have a few questions.

This is what I know so far.....
They have 4 wire leads
No permanent magnets
OEM power was 24v lead acid
The original controller fed 24v to the field and did not vary the field voltage as far as I know of
I do not need to vary the speed or reverse the motors

So here are a couple questions
How should I wire the switch?  I assume a 2x 2 pole relays would be ok
Do I need to control the voltage or current to the field?  Do I need a cap across the leads?  Any ideas of a fuse size?
What is the best way to optimize power?  Increase the field voltage?

Any info about this would help



Thanks
Chuck

Title: Re: Using Sepex DC motors
Post by: machmanchuck on May 04, 2010, 05:32:41 PM

no one has done this???????

Title: Re: Using Sepex DC motors
Post by: tmoney68 on May 04, 2010, 08:57:16 PM

I think 2 of the wires are for the electric braking, at least they were for mine. I took the brake off and just used the 2 wires (pos. & neg.) to power the motors

Title: Re: Using Sepex DC motors
Post by: machmanchuck on May 09, 2010, 10:39:53 AM

Thanks for the reply, but I am certain that the second wires are for the field excitation. 
From what I have read this motor type is quite common in wheelchairs, so I am surprised no one has used them.

Chuck

Title: Re: Using Sepex DC motors
Post by: antom on May 18, 2010, 09:42:45 PM

I concur that 2 of the leads are for field excitation. Wound field motors are not as popular as they once were. Permanent magnet seem to dominate the market now.
A fixed voltage of 24vdc would work just fine for full torque operation. There are a few tricks that can be done with "field weakening". This is used to get more rpm above the base (standard) motor speed. With NEMA class motors they are balanced for operation 2 times the name plate rpm.  Lowering the voltage to the field also will decrease the torque which could have been used to make the operation less easier to control.