RE: (ET) Shunt or series

Here is how I think of a series motor. Because the armature current goes through the field windings, when the load drops on the motor, the amps in the field drops (just like field weakening on our traction motors). The lower the load on the motor the more field weakening. A series motor rated for 2 hp at 3000 rpm can easily tripple it's speed under low load 1/4 hp for example. Its usually a bigger deal for larger motors than small motors. So even at its rated voltage if it is more than a small fractional motor you need to watch for run away conditions.

The snow blower was originally designed for a gas motor 3600 RPM no load, maybee 2600 rpm at max torque load. The GE motor mimics this type of speed. A pure series might try to go to 9000 RPM even with the chain and blower intact. Then down to 2500 RPM under load. Not a great motor for the application without a controller etc.

T Humphrey <thumphrey mynra com> wrote:

I'm not sure about this but I think that if a series motor is kept
around it's nameplate voltage then it won't have a problem with
runaway. The problem comes from using a series motor on a much
higher voltage as is done in EV's to get much greater power out of
them.

I am going to try to use a snowthrower motor on my kids jr
draster, I will power it with much more than 36v. I currently have
6 13ah Hawkers that I plan on using i.e. 72v for a start. I hope
nothing breaks as this will probably overspeed the motor. if
successful I may go up to 144v in 12, 24, or 36v steps. Knowing me
it will probably be two 36 v steps.

I am sure I will need to modify the motor to cool it, since it
runs hot even in the winter. Then again I may ask my
neighbors(Advanced DC Motors Inc.) if they would like to help us
out a little

Does anyone know the ratings on these snowthrower motors, or the
brush numbers?

Stay Charged!
Hump

---------- Original Message ----------------------------------
From: Humphrey Timothy H Contr AFRL/IFEC
Date: Tue, 27 Jan 2004 18:55:24 -0000

>
>
>-----Original Message-----
>From: maxmatic comcast net
>To: elec-trak cosmos phy tufts edu
>Sent: 1/27/2004 11:20 AM
>Subject: Re: (ET) Shunt or series
>
>It is, indeed, a series-wound motor.
>
>Doesn't this hint that the guys at GE thought the problem of
run-away in
>a series wound is overrated? I mean, in an app where the load can
easily
>be lost (the chains do break... one has on me!) shouldn't they
have used
>another configuration? (And the motor survived, by the way, in case
>anyone was worried.)
>
>Or, ha ha, is it a little spare parts prob/stats application!?
("Chain
>broke? You'll need a new chain, and, er, lemme see, says here a new
>motor, too...")
>
>-Maxo,
>who loves the wealth cheap and available series wound motors,
>who has never destroyed one in a run-away,
>but who is careful just the same.
>
>--
>http://www.maxmatic.com/
>> Series motor.
>>
>> - SteveS
>> E20
>>
>> ----- Original Message -----
>> From: "Chris Zach"
>> To: "Elec-trak list" <>
>> Sent: Monday, January 26, 2004 10:07 PM
>> Subject: (ET) Shunt or series
>>
>>
>> > Quick question: Is the motor on the snow blower a series
motor or a
>> > shunt wound one?
>> >
>> > I'm curious because I noticed that after plowing this morning the
>plow
>> > refused to spin up. Just a little grunt and nothing. The
chute was
>> > clear, as was the auger. The reset button was not out.
>> >
>> > I realized the problem was the batteries were low to the
point where
>the
>> > motor probably couldn't get it's field up and going to start the
>> > armature. So I drove it down to the outlet, charged, and
everything
>was
>> > fine.
>> >
>> > Odd.
>> > Chris
>> >
>> >
>> > _______________________________________________
>> > Elec-trak mailing list
>> > Elec-trak cosmos phy tufts edu
>> > https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
>> >
>> >
>>
>>
>> _______________________________________________
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Try it!

References:

RE: (ET) Shunt or series
- From: T Humphrey