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.

 

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..

 

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
.
.
.

 

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.

 

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.

 

I also looked up the type of resistor I have here and I make them 22ohm. Maybe someone could confirm I read this correctly.

 

Yes 22ohms 5%,

 

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.

 

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.

 

Does the size of the resistor matter? I can't find any that are as big as the ones on my board, they are 18mm long in the body.

 

Looks like a 3W type, so any Wattage higher will do.

 

So, I couldn't see how to attach a video so here is a link to it on my Google drive. I hope it gives the information you guys need, if not then shout and I'll have another go.

I have ordered some new resistors and fuses and I also bought a phase loss protection relay.

https://photos.app.goo.gl/XWZJXxYoLqjxf7mt6

 

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.

 

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.

 

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.

 

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.

 

The Transformer is set to 380V , what is the mains supply where you are?

 

The Transformer is set to 380V , what is the mains supply where you are?

Mains supply is 415v

 

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

 

I would wire the phase relay in series with lid micro switch, so that in the event of a phase going down the machine will stop.

With all 3phases there the NO contacts will be closed, and the NC contacts will be open.