Can anyone help me fix this circuit board please?

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
This is the circuit board from my motorcycle wheel balancer, it is a 3 phase machine. The area circled in red, I think they are resistors, two of them have burn marks on them. I'm happy to replace them, maybe all three but I need to find out what caused them to burn out.

The area circled in yellow, these were two, 2A x 250v fuses and both of these had blown.

I don't really know where to go from here but I am really hopeful that someone can suggest what to check and maybe point me to the cause of the failures here.

I am not an electrical engineer but I'm happy to get going to repair this board so I can get my wheel balancer going again.

Thanks, Daniel.

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LowQCab

Joined Nov 6, 2012
3,937
The "2" Resistors probably burned-up from the Machine temporarily loosing
Voltage on one of the 3 Phase-Legs feeding the Machine.
This will instantly cause the Motor to "Lock-Up" and pull the full "Locked-Rotor-Amps" from the Supply.
This usually results in one, or several Fuses being blown, or a Circuit-Breaker being tripped.

You can devise your own "Phase-Loss-Detector" from several Relays,
or purchase one ready-made,
to prevent this from happening in the future.

The Resistors are probably slightly underrated on purpose to act as "fuses" in this exact scenario.

After You have effective "Phase-Loss-Protection" in place,
I would suggest bumping-up the Wattage-Ratings of the new replacement Resistors.
Just remember that the Resistors could be underrated to protect everything else on the Board.

A higher-quality Machine would have come equipped with Phase-Loss-Protection built-in.

ALL 3-Phase-Motors need Phase-Loss-Protection,
it can be very simple to implement with a minimum of 2 ordinary Relays,
or, there are more sophisticated commercial units that
also protect against over and under-Voltage conditions as well.

Phase-Loss-Protection-Relay
.
.
.
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
Need to know what plugs into the the 4 pin socket on the top, as it looks like the resistors are in series with the grey capacitors for suppression..
Hi, the 4 pin block connector marked in blue, if thats the one you are referring to, goes directly to the motor and the 4 pin connector marked in orange is power in.

PXL_20231109_193820962.MP1.jpg
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
The "2" Resistors probably burned-up from the Machine temporarily loosing
Voltage on one of the 3 Phase-Legs feeding the Machine.
This will instantly cause the Motor to "Lock-Up" and pull the full "Locked-Rotor-Amps" from the Supply.
This usually results in one, or several Fuses being blown, or a Circuit-Breaker being tripped.

You can devise your own "Phase-Loss-Detector" from several Relays,
or purchase one ready-made,
to prevent this from happening in the future.

The Resistors are probably slightly underrated on purpose to act as "fuses" in this exact scenario.

After You have effective "Phase-Loss-Protection" in place,
I would suggest bumping-up the Wattage-Ratings of the new replacement Resistors.
Just remember that the Resistors could be underrated to protect everything else on the Board.

A higher-quality Machine would have come equipped with Phase-Loss-Protection built-in.

ALL 3-Phase-Motors need Phase-Loss-Protection,
it can be very simple to implement with a minimum of 2 ordinary Relays,
or, there are more sophisticated commercial units that
also protect against over and under-Voltage conditions as well.

Phase-Loss-Protection-Relay
.
.
.
Looks to be a good investment and easy to install too. Thank you for the advice, I will get one.
 
Maybe I know a little about your problem. Voltage on one of the machine's three-phase legs.
The Motor will immediately "Lock up" as a result, pulling all of the "Locked-Rotor-Amps" out of the Supply. Usually, this causes a circuit breaker to trip or one or more fuses to blow. Voltage on one of the machine's three-phase legs.
The Motor will immediately "Lock up" as a result, pulling all of the "Locked-Rotor-Amps" out of the Supply.
Usually, this causes a circuit breaker to trip or one or more fuses to blow.
Circuit-Breaker to prevent over-supply voltage.
 

LesJones

Joined Jan 8, 2017
4,172
Looking at the common mode filter on the board it looks like the board is fed between one phase and neutral. (It looks like the capacitors in the filter are rated for 250 volts.) I suspect thet these fuses do not suply the three phase motor. (I am assuming you are located where phase to phase voltage is about 415 volts and phase yo neutral 240 volts.)
I think the original fault is on some other part of the machine. Can you post a schematic of the machine or at least give us some idea of what else is in the machine as well a 3 phase motor. I imagine there will be some electronics to detect inbalance.

Les.
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
Looking at the common mode filter on the board it looks like the board is fed between one phase and neutral. (It looks like the capacitors in the filter are rated for 250 volts.) I suspect thet these fuses do not suply the three phase motor. (I am assuming you are located where phase to phase voltage is about 415 volts and phase yo neutral 240 volts.)
I think the original fault is on some other part of the machine. Can you post a schematic of the machine or at least give us some idea of what else is in the machine as well a 3 phase motor. I imagine there will be some electronics to detect inbalance.

Les.
Hi Les, thanks for your reply. I will be at my workshop this afternoon and I will take a video of the inside of the machine and its components.

Thanks, Daniel.
 

LesJones

Joined Jan 8, 2017
4,172
Can you mark up your picture in post #4 showing what each of the white connectors connect to?
I assume that the one circled in blue goes to the isolator switch. Are the 3 black wires to that connector the 3 phases and is the brown wire neutral ?
Can you post a well focused picture of the transformer so can read the markings on it ?

Les.
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
Can you mark up your picture in post #4 showing what each of the white connectors connect to?
I assume that the one circled in blue goes to the isolator switch. Are the 3 black wires to that connector the 3 phases and is the brown wire neutral ?
Can you post a well focused picture of the transformer so can read the markings on it ?

Les.
No problem, I will do that tomorrow.
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
Can you mark up your picture in post #4 showing what each of the white connectors connect to?
I assume that the one circled in blue goes to the isolator switch. Are the 3 black wires to that connector the 3 phases and is the brown wire neutral ?
Can you post a well focused picture of the transformer so can read the markings on it ?

Les.
So the block connector marked in blue goes to the motor. From memory the colour of the four wires going to that block connector from the motor are all different colours. Im not sure how to ID the neutral in the bunch. I'll post more pics tomorrow.

Thanks for your interest.
 

Thread Starter

DanielHowden

Joined Nov 8, 2019
65
I took some photos today and I annotated them. I hope I have answered the questions being asked. If not please shout me.

I really appreciate the help here, Daniel.

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Thread Starter

DanielHowden

Joined Nov 8, 2019
65
LowQCab - can you please advise on how I wire up this item and where in the wiring I put it.

I don't understand the wiring diagram on the side of the unit.

Do I wire it in between the power in and the circuit board?

Thanks Daniel

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