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Electric Motors/4 wire electric motor


QUESTION: I am working on an old centrifuge that is powered by a 110 input to a transformer that feeds a 220v  1 phase motor. The 220 feed off the transformer goes to a confusing circuit board that recently started smoking and caught fire. I am confident that the motor is still good and was wondering if I can bypass this circuit board. this motor is made to spin at 3000 rpm and has a braking system on the switch. I can do without the braking system and really can not figure what else requires  this intricate circuitry. If it is possible to bypass how do I connect the 2 wires from transformer to 4 wires on the motor.

ANSWER: Terry,  so your connection terminal board caught fire,  probably from a loose carboned connection on the board,    carbon builds up under the boards, loosens the connections and it can cause everything from a burned carbon track to a burning board,  

So you have four motor leads left from the board,  plus maybe some others that controlled the brake?

Do you have a capacitor,   any numbers or letters on the board?  Any name plate data on the motor,    was it dual voltage,  reversible or both?

Are you positive the 220 only went to the motor with the four wires?

It could be that the four are used to be put in series or parallel for dual voltage,  it could be two are for the cap and two are for line,      

Can you measure the ohms between the leads,    even if arbitrary,    ohms from say  1 to  2     1 to 3   1 to 4  so on,    some may not have a circuit,  but I need to know that,     I need anything  you can give me as far as numbers or how they were possibly connected before,    plus the questions above, to figure out what type of motor and what possible connection conventions we need to start with,         let me know all you can       and we will make some attempts   

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QUESTION: sorry to take so long to get back, your reply ended up in spam mail and i could not find it. the 4 wires to motor are blue,black,brown and ground.
ground has no continuity with other 3. brown and black has 20 ohms, brown and blue is 20 ohms, blue and black has 7 ohms. this has a four wire switch that has 2 positions, 1 spends the motor and other is a brake.

The capacitor has uf 25 on it. 400 volt db hsfpu, hsfqv, hpfnt.
The motor is marked 1 phase, hz 50, cond uf 16, tipo 70/8

I am guessing the brown wire is a part of the brake circuit and the reason for the circuit board.

ANSWER: Terry  something doesn't add,    you have four wires,   one is chassis ground,   that leaves three to the motor,    because the three remaining all have continuity with each other, they are three motor leads,     and the ohm values are odd for a PSC type motor,  [permanent split capacitor]

Should be a common,   a start and a run,   but the double 20s is throwing my diagram off,  

Also you say it has a 25uf cap  yet the nameplate says the cap should be 16uf

Are there brushes in this motor?   Can you recheck the ohm values for me?  A difference of a few ohms could change things a lot,     

But with blue, black, and brown  all tied together,   either there is another component in the mix  because just wire  ohmage  is not adding,  

I will have to research that switch more also,      

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QUESTION: I am sure of the ohm readings, not sure how to tell if motor has brushes,

I am unclear how a motor brake is supposed to work but i am curious about the 3rd wire in this motor

ME too,    the third wire is the brake  and how did you determine that?   The ohm readings with two at matching and one that would not be in parallel does mean there is something else in that entire amount of ohms,          so I am thinking blue is the brake,   or somehow associated with the brake,    there are generally two types of brakes,    one is a mechanical brake with a coil that when energized or power is removed,  releases or pulls a brake plate in with friction disks,   the other type would be some sort of dynamic brake where the poles that produce rotation are immediately reversed,      putting a reversed pole or total winding in the opposite polarity, which grabs the rotor and is a pretty quick and violent stop,          is there anything spring loaded or mechanical on the end of the motor?

At this point I still have no idea what configuration you have, nameplate, brand,  etc,      but the ohm readings you gave me  tell me something is special and tied into the main windings,  

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Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site


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