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View Full Version : how do you visually distinguish induction-type motors from brush-type?



Chunkstyle
09-27-2005, 01:08 PM
hi guys

can any of you please tell me if it's possible to tell whether a motor is induction-type or uses brushes, just from looking at it?

i've got this motor that i'm hoping to use on a hobby lathe with a router speed control to help drop the rpm's lower than the stock step pulleys allow, but was told here that such a control won't work with an induction motor.

i looked at it, and the motor's info is:

delco "thermotron"
type m
model ra8401x

there's no obvious outward access to brushes (not sure if all brush-type motors have external brush access anyway), nor is there an evident starter capacitor.

can anyone please tell me which this is?

thank you!

Steve Stube
09-27-2005, 01:12 PM
Not to mention Induction-Repulsion types that are both.

Evan
09-27-2005, 01:31 PM
If it makes radio noise at speed on an AM radio it has brushes.

Mariss
09-27-2005, 02:51 PM
Connect it to +5VDC. If it turns, it has brushes.

Mariss

ibewgypsie
09-27-2005, 03:44 PM
If it has screw in brush carriers then it is a brush type. they sometimes look like a bump with screws radially around them..

If you hook a meter to it, and spin it, a permenant magnet field motor will generate a voltage.

I recently did a stepper like this determining the 8 wire series hook up.. yeah that was a ordeal.. Kinda like a Mensa test. Wrong polarity? it'd counter act the other field and not generate voltage.
It worked. I hunted for two days for information on the net, even Asked Mariss there..

Yeah, Mariss, glad to have you around, you are a positive influence here.



[This message has been edited by ibewgypsie (edited 09-27-2005).]

J Tiers
09-27-2005, 10:38 PM
Very simply.... look in the end (usually the one away from the output shaft).

If you see a copper ring made up of segments parallel to the shaft, its a brush type.

Brush type stink for lathes, because the speed regulation is horrible. Normally they are "series universal" motors, and need some sort of controller and speed feedback to hold a steady speed.

Your machine has 6 speeds, 3 faster using teh pulley steps, and 3 slower with the same steps, but the planetary backgears engaged. An induction motor and no speed control should work fine, if you have both pulleys. A 1/4 HP 1725 rpm will be fine.

There is a manual for that 109 on the metalworking dropbox, I think in 1999 retired files. Also some other info. Should be called "AADOCS".

Paul Alciatore
09-28-2005, 10:31 AM
Brush type motors are usually easy to spot. Larger ones will almost always have provision for easily changing the brushes so look for TWO bumps or screw heads spaced 180* apart on one end. Smaller ones usually have vent holes and you can see the brushes or the windings on the armature. Any armature wound with multiple turns of relatively fine wire will have brushes to get power to those windings. Induction motors can have a single turn winding of heavy gauge copper so don't be fooled by that.

Oh, if it is DC, it is usually a brush type but there are some exceptions here - usually expensive exceptions.

Paul A.


[This message has been edited by Paul Alciatore (edited 09-28-2005).]