MOTORS and Centrafugal Switch Doofers

[aboard_epsilon]

I posted this further down the page looks like no one seen it.
Can anyone explain simply how a centrafugal switch works to me ..thats if this thing im abvout to describe is one..
This fritz I'm doing up has some sort of doofer bolted to the end of the armature shaft on the outside of the motor that looks like a mini generator,with what looks to be like a comutator in the middle with two magnets on the outside.
the commutator bit does not have any feed or return electrically......dont know what's behind the magnets .....but wiring exits from behind them.....and the wiring then goes into the main electrical cupboard.
how does this lot work ...I need to know because someone has bi-passed a lot of stuff in the electrical cabinet.
I like things to be original..it just pleases me.
I just love the old frankenstein electrical gear it just looks so powewrfull and forbidding and was probably very expensive in its time.
anyone ever seen one of those mercury vapour rectifiers in action...a sight to behold!!!
also does anyone in the uk have any siemens rotary drum switches and contactors from the late forties early 50's in good condition in the uk.
all the best..mark

[This message has been edited by aboard_epsilon (edited 06-12-2005).]

[John Stevenson]

Doesn't sound like a centrifugal switch.
Is this a 3 pahse motor ?
if so they don't have cent switches.
Could be some form of brake or tacho but no idea why they would want a tacho.

Pics if you please.

John S.

[aboard_epsilon]

Will get some pics of it tommorrow John
and thanks for the manual scans they will come in very handy .not had a chance to have a look at them yet ...
yep your right about the three phase motors not having the swich...you only here the click on single phase motors .
this is a three phase motor on this machine.
all the best.mark

[This message has been edited by aboard_epsilon (edited 06-12-2005).]

[Yankee1]

Hello Mark,
In reply to your question. A centrifugal
switch is a mechanical device that consists of weights,springs and a set of electrical contacts. The springs hold the electrical contacts closed and electricity passes through to a startup winding to provide extra torque for startup. When the motor starts and the weights which are acted upon by the centrifugal force overcome the spring tension holding the contacts closed the circuit opens causing the starter winding to become deenergised.

[Forrest Addy]

Sounds like a resolver to me.

[aboard_epsilon]

OK pics as promised
This is the commutator doofer that I've just placed temp on the end of the motor shaft for the pic so you can see how its mounted.....not present in this shot is the fan and the outer shroud..the commutator is usually on the outside of these.


This is the housing the slips over the commutator thingy......


Inside the housing are these two magnets .sort of


A view inside the electrical cabinet.


Overal view


can anyone make head or tail of this ....especially the lower right and upper right



all the best..mark

[This message has been edited by aboard_epsilon (edited 06-13-2005).]

[Toolbert]

My guess is a zero-voltage detector, originally operating an interlock to prevent speed changes or other control changes while the spindle was rotating. It would have enforce waiting for the spindle to come to a stop after turning off the motor. If so then it broke and was bypassed leaving it to the operator to observe spindle stop. To be sure I'd need to know more about the machine controls. regards, Bob

[aboard_epsilon]

-two motor speeds forward and two motor speeds reverce.
not sure at present if this device has been bypassed.
something has been in the box there are jumpers there.
will have to maybe learn by conecting it all up as it should be... then ..find out whats not functioning.
all the best.mark

[J Tiers]

Toolbert may be onto it.

That looks like a squirrel-cage rotor, which suggests that it acts as an induction generator to give a control voltage, maybe for a tach, maybe for an anti-plugging interlock, or both.

I and II are Cw and CCw rotation conditions, based on the power relay wiring next to teh pump on teh diagram. Two lines are interchanged.

[aboard_epsilon]

Yup I agree with toolbert.
it's not a tacho, as the tacho would only read two motor speeds and not the spindle speed ..of which there are with the change gears and the back gear about 24 speeds.
can you point out on the circiut diagram which circuit the device is on..I cant see it there.
all the best.mark