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Discussion Starter · #1 ·
To Whom it may concern,

I am from South Africa. We have a church bell with a 3-phase electric motor. The motor is connected to the bell via a chain over a small sprocket (gear) on the motor shaft and a large wheel driving the bell. The motor was refurbished recently, but since re-installation, the motor reverse function will not operate correctly.

It has an electromechanical change-over system attached to the rear of the motor, working on a pendulum and cams to effect the change-over to reverse the direction of the motor. Upon start up the first set of contacts are closed. When the motor has turned far enough for the bell to reach the desire angle of replacement from horizontal, the first cam causes the contacts to open, the weight of the bell then should start forcing the motor to turn in the opposite direction. As the first set of contacts have opened, there is no supply to the motor. All still well. At this stage the pendulum (inside the motor control) swings over to close the set of contacts on the opposite side. This causes a reverse of two phases which will then correspondingly reverse the direction of rotation of the motor to be the same as the forced direction due to weight of bell. This will now cause the motor to swing the bell through equilibrium to the opposite side until the same negative angle of rotation is reached. The second cam then causes the pendulum contacts to open, pendulum releases and whole process starts over again in reverse direction until electric supply is switched off.

Problem starts with first change-over. Cam causes contacts to open, pendulum swings over, make contact on other side, but doesn’t remain in position. It immediately swings back and close first set of contacts, causing motor to keep on turning in original direction.

I have been searching the web for hours-on-end and can not find an answer. Do you maybe know the system or where I can get more information regarding this, even a repair company in South Africa.

We can install an electronic controller, but would rather keep the installation as original as possible.

The installation is ±30 years old. The manufacturers plate was removed sometime in the past but on the casing of the motor the name “VOCO” is imprinted. The motor with the electromechanical controller forms a single unit.

Any assistance will be highly appreciated.

Regards/Groete

Christo Nortje

(Pr. Eng.)
(for MAPULE CONSULTING/NORTJE & ASSOCIATES)

Tel. No.: (011) 362-1829 102 – 5th Street P.O. Box 1300
Fax No.: (011) 362-3852 SPRINGS SPRINGS
Mobile : 082-468-2730 1559 1560
e-mail : [email protected]
 

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From your description, I would check the cam switch function and make sure that the reversing starter is working properly with no faulty contacts. Is it possible to disconnect the motor from the load (the bell) and cycle everything by momentarily jumpering the cam switch contact?

It is possible that the reverse contactor has a burt out/worn contact and when the contactor pulls in, to reverse the motor, it is causing a "single phase" condition to the motor. If so, this could have been the reason for the initial motor failure. It could also be the coil in the reverse contactor not functioning.
 

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Discussion Starter · #7 ·
Church bell controller

Thanks for the feedback, but there are no contactors, only the contacts on the electromechanical controller. I have made a rough drawing of the controller side (Back view - looking towards motor), with a simplified wiring diagram and a description of the operation. If somebody reconise this, maybe we can find some instructions on how to set the cams and what the influence of the counter weight is.
 

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If this is all there is to the control, then the cam switch contact for the reverse direction is not working and COULD have cased the original motor failure. The cam switch contact(s) could be burnt up, worn out or the cam could be out of adjustment.

As a test, could you reverse the incoming phases and run the motor in the opposite direction first? This would depend on what mechanically is driving the cam switch if this could be tried.

From your drawing the cam switch must be the problem because: You seem to have the proper voltage and phasing as the motor runs fine in one direction. (The motor does not care which way it runs.)

What size (KW) motor are we talking about? Plugging a motor forward and reverse repeatedly is a brutal application, but I suppose that this normally happens no more than 12 times an hour. Still, over time the motor and control contacts take a beating.
 
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