Electrical Snow blower motor -- why two windings?

[John1397]

TL;DR Summary

Why does switch have normal open and normal closed contacts

I have my field windings on the bench and it has a heavy and light wire wound in pareral there are three wires off the field windings . It looks like to me after testing switch with ohm metter positive turns on motor but when switch is in on position green wire off switch is not connected to smaller wire in field windings , but when switch is off there is connection from ground thru field then to ground. I can't figure out what is the smaller winding in the field used for? The bearing went out in motor and windings got hot wires are still good looking but the small and larger field windings are shorted together but not to ground. When I get my bearing I will run motor to see if it works and run with large field winding connected to AC and leave small wire in field disconnected. I do not have ringer so can't test field.

 

[jedishrfu]

According to this article double winding motors are cheaper to make:

https://www.quora.com/What-are-the-...nding-in-an-induction-motor-and-an-alternator

 

[John1397]

My mistake when testing two field windings against each other for short they would test shorted as they are connected together on other end.

 

[Tom.G]

Could be a few things:
Start and Run windings
Dual Speed
Dual Voltage
Dynamic Brake

How about supplying a schematic or wiring diagram showing the two windings, the switch with any labels or markings, and where the incoming power is connected?

Also does the motor have brushes to make electrical contact to the rotor? If so where are they wired?

Cheers,
Tom

 

[John1397]

Could be a few things:
Start and Run windings
Dual Speed
Dual Voltage
Dynamic Brake

How about supplying a schematic or wiring diagram showing the two windings, the switch with any labels or markings, and where the incoming power is connected?

Also does the motor have brushes to make electrical contact to the rotor? If so where are they wired?

Cheers,
Tom

 

[jim mcnamara]

@John1397 - you posted an airball. Just a copy of a previous post - no content from you. Please try again.

 

[John1397]

I posted picture above it is crude. I can see current comes in thru switch to field then to brushes on to armature then to fuse then on to ground when running, this makes sense to me.

When switch is in off position ground goes thru switch to second smaller winding in field windings and both windings coming off field are connected together then attached to brushes. I was thinking if the one part of switch does not open when turning off then the second part of the switch applies ground to the smaller diameter windings to slow or stop motor but I do not know what this would do.

I have worked on motors with two set of windings but they have switch on armature when speed comes up to break contacts but mine is just plain brush type armature.

 

[John1397]

Better drawing

 

[Asymptotic]

Better drawing

According to the drawing, when switched to 'on', current flows through the motor armature and heavier windings. When switched to 'off', this circuit is broken, and motor armature is connected through the lighter windings through the closed switch element and would act as a dynamic brake.

When the snow blower was operating did the motor stop turning nearly immediately after switching it off?

 

[John1397]

According to the drawing, when switched to 'on', current flows through the motor armature and heavier windings. When switched to 'off', this circuit is broken, and motor armature is connected through the lighter windings through the closed switch element and would act as a dynamic brake.

When the snow blower was operating did the motor stop turning nearly immediately after switching it off?

I never used it just got it broken. I see now the armature when spinning it generating electricity then when you ground every thing out it stops faster. Would not stop any faster under full load though.

 

[Asymptotic]

I never used it just got it broken. I see now the armature when spinning it generating electricity then when you ground every thing out it stops faster. Would not stop any faster under full load though.

True enough, but providing a fast stop under unloaded conditions improves safety.

I don't recall the particulars, but for industrial systems OSHA requires certain types of machinery (pull rolls, rotary presses, and the like) to stop completely within a rather short travel distance after the 'stop' switch has been pressed, and doing it required dynamic motor braking, a mechanical brake, or combination of the two.

 

[John1397]

I seen diagram for stopping bench grinder you use diode to apply DC to brushless ac motor to stop it never made it though do not know if diode would work on brush type motor.