Need 3 phase wiring help! Agazzani bandsaw

Hi All,

Thanks in advance for reading this post and providing any guidance.

I am working on a friends newly acquired 24" bandsaw and I have been unsuccessful at getting it wired back into operation after the motor was removed and serviced.

It has a star, delta switch and a separate overload protector switch.

It also has a power actuated brake built into the motor, this is working properly.

I can wire the star power wires with the delta wires disconnected and the motor runs, and runs in the correct direction. There was a photo of these wires before the motor was removed so I am 100% sure that these wires have been restored to their original position.

I can wire the delta power wires with the star wires disconnected and the motor runs and in the correct direction if I wire this in a sequence that works for this. eg 321, 213, 132.

The problem is that with both the delta and star wires connected, the overload protector immediately triggers as soon as I try to run the motor by turning it on in the first switch position (star).

I admit that I am not experienced with wiring machines of this type, but I do have electrical experience and I can run tests if anyone knows what might be wrong here. I believe I have tried every forward running combination of the delta wires but the result is always the same, the overload protection trips.

The switch wiring is a bit complicated and I don't know what the internal connections are supposed to be in the star and delta positions.

Thanks again for having a look.

Bump

begin with confirming with the shop that rewired it, that the existing motor connection tag is still correct
if no, ask for correct connection diagram
if yes, look at the motor tag
next look Carefully at the diagrams on the following posts
determine which diagram below applies to your motor (voltage, no. of motor leads, etc.)
as well as your contactor setup (how many contactors with how many poles used)
VERY carefully double check your wiring, obviously you have looked once so use more care this time
take Several Good pictures with different angles, be certain you can put it back before you change anything

study the diagram and understand the correct operation of it

the purpose of the wye start / delta run connections is to momentarily wire the motor so that it only needs a portion of the full load amps to come up to partial or full speed, depending on the motor
the motor connections must be changed by the engaged contactors for EITHER start or run

the control circuit must be wired correctly to the contactors
there must be a timer set to the correct value for all part winding start set ups
if there is no timer the operator must understand the function of his controls to time the changes properly
(listen to the motor and change to run as soon as acceleration is completed)

some of the contactors cannot be engaged all of the time and are only used for starting
usually for run there are two 3 pole contactors remaining closed

AR,

Thanks very much for your response.

The diagrams were helpful and I think your comment about the motor shop winding may apply.
Specifically, the connections are on the motor are bridged as shown below from your diagram. In this case, if there is an S3 contactor, the M1 voltage will be driving into a direct short. In one of your diagrams, there is no S3 but I don't know which configuration matches the unit I am working on, I will check.

Don

deklund said:

AR,

Thanks very much for your response.

The diagrams were helpful and I think your comment about the motor shop winding may apply.
Specifically, the connections are on the motor are bridged as shown below from your diagram. In this case, if there is an S3 contactor, the M1 voltage will be driving into a direct short. In one of your diagrams, there is no S3 but I don't know which configuration matches the unit I am working on, I will check.

Don





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i did not know you would be dealing with a foreign motor
i do not have diagrams for those
as long as the original connections to the contactors have not been changed
you should be able to tell what the contactors are intended to do
disconnect the motor leads and watch the contactors as you activate them in proper sequence

your most likely problem is that the jumpers should be removed
the contactors normally take the place of the jumpers and there for they are indeed causing a phase to phase short
try the motor again without the jumpers and see what happens

EU motors use a different wire numbering scheme
as well as a different internal winding connection scheme
this results in the majority of dual voltage eu motors that i have seen having only 6 motor lead connections

however there are some for multi speed and other special reasons that have more connections

AR,

Thanks again for your response. You are absolutely correct that the jumpers needed to be removed. While installed they created a shunt to ground from the leads carrying current from the star position of the switch. After studying the diagrams you sent as well as others found online this was the obvious answer. What made it confusing is that this was the way the equipment was presented to me and I was told that nothing had been altered. With the jumpers removed and the star, delta pairs identified, the motor works perfectly with a manual run up to speed in star mode and full run power in delta mode.

Don