Fault finding on star/delta starters

[glenn1340]

I would guess most of you already know of this here`s a trick I often use for helping in fault finding on star/delta starters.
If you suspect a fault on the shutdown circuit that can`t be found with the motor off try removing one of the solenoid wires on the main contactor. The star and delta contactors will still operate and all the other circuits will be in operation. The idea behind this is that the motor will NOT be running so you can stop an start the machine as often as you like to do testing without the very real danger of damaging the motor.
Now, this doesn`t alway work as some machines need feed back signal from the main contactor to allow the other contactors to operate but as it only takes two minutes to remove a wire so it`s worth a try.

[Brian_UK]

What of you have mechanical interlock between the contactors?

[glenn1340]

What of you have mechanical interlock between the contactors?

As I said it won`t work on all systems but I`ve not yet come across a starter that has an interlock between the main AND star or delta contactors as the main would need to be in all the time to enable the motor to run. The other two contactors would operate in the normal way regardless of whether the main contactor is pulled in.

[Brian_UK]

^^ True, I'll go sit in the corner for a while.

[frank]

I always remove the wires to the motor when watching the control sequence operate. Same thing really, no power to the motor.

[Quality]

Franks method is better than removing control circuit control wires at least with the motor disconnected every thing else should operate as it should if its ok.
If it dont then there you go

[glenn1340]

Franks method is better than removing control circuit control wires at least with the motor disconnected every thing else should operate as it should if its ok.
If it dont then there you go

Granted, but how long can it take to remove the leads on a 340hp motor which is the stuff I work a lot on? A lot longer than one .75 wire. As I said it`s just a quick way of trying to narrow down a fault on overtemp switches o/loads and E stops etc. without over starting the main motor.

[goshen]

I would guess most of you already know of this here`s a trick I often use for helping in fault finding on star/delta starters.
If you suspect a fault on the shutdown circuit that can`t be found with the motor off try removing one of the solenoid wires on the main contactor. The star and delta contactors will still operate and all the other circuits will be in operation. The idea behind this is that the motor will NOT be running so you can stop an start the machine as often as you like to do testing without the very real danger of damaging the motor.
Now, this doesn`t alway work as some machines need feed back signal from the main contactor to allow the other contactors to operate but as it only takes two minutes to remove a wire so it`s worth a try.

Hi this is a good idea, however most units will not leave the system energized for more then a second, if they do not detect current flow!!!this applies to trane -carrier york and a few more.:)

[Lodiev]

It starts at the planning of the main and control wiring of the starter panel, I will normally split the controls from the main wiring to enable me to switch off the main supply to the contractors thus enabling me to test the control circuit on its own without the motor running. The micro processor will stop the starter again but their is a way to solve this with a resistor at the right place creating a false current for the micro to read that the motor are running.

[goshen]

It starts at the planning of the main and control wiring of the starter panel, I will normally split the controls from the main wiring to enable me to switch off the main supply to the contractors thus enabling me to test the control circuit on its own without the motor running. The micro processor will stop the starter again but their is a way to solve this with a resistor at the right place creating a false current for the micro to read that the motor are running.
Hi one thing in favor of the big manufacturers they all have a pre start test in case of wye delta starting !
i personally try to upgrade all wye delta to soft starters when possible.:D