Can someone tell precisely how to troubleshoot the control circuit in this diagram. I need an expert to help me because i've heard different stories.

 

Don't believe all the stories you've been told
Generally the sequence in any trouble shooting is first to find out what the circuit is supposed to achieve, and then identify the point where the procedure stops, and Then What is supposed to happen next.
This is a general guide line and can be used where the source of the problem is Not obvious such as a smoking coil etc?
If a fuse has blown or O/L has tripped, then identify the most likely suspects of why.
In the circuit example, this method using a meter by logical procedure through the control sequence should indicate the point where the circuit has failed.
Generally the meter common probe would be on the bottom rail and the circuit traced by voltage reading to indicate the point of failure.
In this case the circuit is drawn in the IEC style, proceeding from top down, as opposed to the Left to Right style.
As you can see KM1 should pick up to seal in the start button via KM3, which seals itself in etc.
K1T is the crucial timer that switches over when it times out.
Was this a working circuit?
Max.

 

This is a very simple circuit, check from bottom rail common to K1T contacts in the KM1 and KM2 string to see if KT1 is timing out.
Max.

 

Don't believe all the stories you've been told
Generally the sequence in any trouble shooting is first to find out what the circuit is supposed to achieve, and then identify the point where the procedure stops, and Then What is supposed to happen next.
This is a general guide line and can be used where the source of the problem is Not obvious such as a smoking coil etc?
If a fuse has blown or O/L has tripped, then identify the most likely suspects of why.
In the circuit example, this method using a meter by logical procedure through the control sequence should indicate the point where the circuit has failed.
Generally the meter common probe would be on the bottom rail and the circuit traced by voltage reading to indicate the point of failure.
In this case the circuit is drawn in the IEC style, proceeding from top down, as opposed to the Left to Right style.
As you can see KM1 should pick up to seal in the start button via KM3, which seals itself in etc.
K1T is the crucial timer that switches over when it times out.
Was this a working circuit?
Max.

Thanks Max,

The original drawing of the circuit is lost. We are looking for it. This one looks like the original drawing. I want to make a procedure to test the circuit. Ok but how do i test the coils of KM1, KM2 and KM3.

Situation 1: Let's say motor starts, time relay kicks in but KM2 doesn't respond. I would in that case turn off the power on the control circuit and then do a resistance test on the coil on KM2.

Situation 2: If the motor starts in star but doesn't switch to delta, then i assume the time relay is bad and i would replace it in this case.

Am i on the right track??

 

With modern contactors and timers a resistance test isnt going to tell yoiu much, they will likely have driver circuits built in.
As far as diagnostics go checking for the correct voltage at A1 is usually the best option.
Assuming A2 is at N, or 0V if the control circuit is DC, and A1 has been switched to an appropriate voltage any device not pulled in, or timing, is faulty... simple functional test.

If the expected voltage isnt there then something failed to supply or switch it.
If your having problems then pull the motor fuses and run the control circuit to check its sequence of operations.

You didnt say what was wrong... If it is working what do you want to check?
If you are asking what could be wrong then essentally anything.
Any contact could fail to open or close and any contactor, relay or timer could fail to work even if it has a supply.
For example the timer might run and give you a light telling you it is timing and then subsiquently timed out, but that is no guarantee that its contacts actually switched if they have been weldeed shut or blown off or even just dammaged so that they present a high resistsance and supply a reduced voltage to whatever is attached.

You 'could' calculate all the possible scenarios but why would yiou want to? It would probably take much longer and be much harder than simply checking voltages and the operation of the various parts with the circuit running.

Al

 

. I want to make a procedure to test the circuit. Ok but how do i test the coils of KM1, KM2 and KM3.

Situation 1: Let's say motor starts, time relay kicks in but KM2 doesn't respond. I would in that case turn off the power on the control circuit and then do a resistance test on the coil on KM2.

Situation 2: If the motor starts in star but doesn't switch to delta, then i assume the time relay is bad and i would replace it in this case.

Am i on the right track??

It is rather a simple circuit, once KM3 seals in then power is applied to K1T, so if the K1T N.C and N.O that supply KM1 and KM2 do not switch over after the time delay then KM2 will not pick up, as Before a simple voltage check at the relevant points of each string to both KM1 and KM2 will show exactly where the problem is.
Max.

 

http://www.tech-service.net/Troubleshooting/six_step_troubleshooting_process.html

 

With modern contactors and timers a resistance test isnt going to tell yoiu much, they will likely have driver circuits built in.
As far as diagnostics go checking for the correct voltage at A1 is usually the best option.
Assuming A2 is at N, or 0V if the control circuit is DC, and A1 has been switched to an appropriate voltage any device not pulled in, or timing, is faulty... simple functional test.

If the expected voltage isnt there then something failed to supply or switch it.
If your having problems then pull the motor fuses and run the control circuit to check its sequence of operations.

You didnt say what was wrong... If it is working what do you want to check?
If you are asking what could be wrong then essentally anything.
Any contact could fail to open or close and any contactor, relay or timer could fail to work even if it has a supply.
For example the timer might run and give you a light telling you it is timing and then subsiquently timed out, but that is no guarantee that its contacts actually switched if they have been weldeed shut or blown off or even just dammaged so that they present a high resistsance and supply a reduced voltage to whatever is attached.

You 'could' calculate all the possible scenarios but why would yiou want to? It would probably take much longer and be much harder than simply checking voltages and the operation of the various parts with the circuit running.

Al

Thanks, i'm beginning to understand this a bit.

 

It is done very simply by measuring the relevant voltages at each point in the circuit, WRT the common, -ve or neutral as the case may be in a logical manner.
Max.

 

http://www.tech-service.net/Troubleshooting/six_step_troubleshooting_process.html

Very good article. Thanks

 

No problem. Apply it to your circuit.

 

@Robesim


As drawn you have a problem. Of course this might be the troubleshooting problem. Can you describe each component on the right hand side, the control circuitry?

For instance: The Stop switch is a normally closed push button switch.

 

@Robesim Obviously the KM3 and KM1 are energizing, It appears that KM2 is not picking up.
From the symptoms it points to either voltage being absent from across the K1T timer (L.H.) rung, which can be checked with a meter, OR the timer itself not timing out, which also can be checked by the voltage from the common rail to the KiT-KM2 junction.
It seems a very trivial circuit to trouble shoot.
I am assuming this is a tried and true circuit that has been working previously?
Max.