wound rotors 1

[fsmyth]

I have the option to get another 20 HP Baldor -
and I really do want to learn more about these
motor types. Quoting a previous post:

" Just got a 20hp Baldor -
286TZ frame, 1425/1675 rpm, spec: 10P46W694,
stk no.: 39H314BAH, 208/240/60 and 220/380/50.
Talked to manufacturer - seems that this was
OEM'd to a mixer company, IIRC. Other than
that, no other specs.

I was hoping that someone had run across this
particular type, and could give me some pointers.
All of the documentation I can find refers to
3-phase rotor and stator windings - note that this
one has only 2 slip-rings, hence only one rotor
winding (more like a 3-phase alternator).
From what I have found, starting a wound-rotor
motor with the armature shorted has a 1000-1400%
starting current (as opposed to 500-800% on a
"standard" squirrel-cage). Is this also true
for this (single-winding) type?
What I need is practical application info, such as
how much resistance to use (near as I can tell so
far, about 3x the rotor resistance), when to switch
it out ( again, NAICT, at over 80% speed), and what
the effects of more slip have on operation.

It appears to my small mind that this could be the
equivalent of delta-Y start, without the massive
switching transient, and (because of more slip)
be more responsive to load variations when used as
an RPC idler.

I can probably interpolate values from a 3-phase
rotor type, if I could just find them. I realize
that this is a small motor for the type - most of
the literature I have found refers to 500HP+, but
any hints are welcome."

Can anyone help, or at least provide some pointers?
I do not mind experimenting, but is is difficult for
me to set up (I have access to 3-phase, but have to
make arrangements in advance, and anything I do will
be in their way until done).

<als>

 

[LionelHutz]

I know it would work edison, I'm just saying a motor operating like that is not a normal synchronous motor. I suspect those motors were custom built for one specific application where they couldn't build a typical synchronous motor that could start the load.

 

[edison123]

Yep. They were for a specific application of a cement mill with a high starting torque requirement.

I just posted to show that such motors do exist and do work.

* Anyone who goes to see a psychiatrist ought to have his head examined *

 

[shagooo]

Electricpete - I think they had three, can't be 100%positive. Typically these motors were used for the high torque applications (high duty cycle, short burst usage)and usually were screamin hot. I would imagine the most durable motors made.
I have also seen the eddy current brakes used with cranes and hoists. These were powered seperately and the same resistor bank/contactor configuration was used but, inversely(and only on the lower command). When the lower button was pushed, minimal braking was needed, as you increased the speed, the brake was working close to make so the load and motor would not "run away".
Interesting thread for an unuasual motor, working on those old cranes and hoist gave insight to speed control and braking amonst other system back in the day.