Winding select contactors are one of the most overlooked items when it comes down to troubleshooting spindle motor failures. Some spindle drives have error alarms that will let the user know there is an issue, but there are also many that do not generate any alarms to indicate an issue with the winding select contactor.
Even though it is uncommon for them to go bad often there are a couple of conditions that can damage winding select contactor, such as under-voltage, over-current, and age. There are a few checks that can be done onsite to ensure winding select contactor is working properly. The easiest check that can be done is once the machine is powered up and spindle drive is in ready status should hear a loud pop meaning winding selector is engaged.
This test may require two people as one person will need to turn the power on and control while the other is in the cabinet listening for the winding selector to engage. If winding, select contactor did not engage next steps will require a wiring diagram or procedure on testing high resistance and low resistance. Some winding selectors will have a sticker of the diagram on the winding selector itself and many others may need to get in touch with the manufacturer for that information.
The first thing to check is whether you are receiving the correct amount of AC voltage. Set multimeter to AC Voltage and measure incoming power to the contactor. Should be around contactor rated voltage. If not seeing voltage or too low of a voltage need to trace cables back to what is supplying the voltage and troubleshoot further. Voltage is present and good next step will be to test low and high resistance, with the only incoming voltage being received low resistance and no 24VDC supply from the spindle drive unit. Low resistance terminals should get a resistance reading, while high resistance terminals should be open.
Next step is to check for 24V being supplied from the drive unit. If 24V source is absent there is an issue with spindle drive unit. To check the winding selector further apply external 24V source to the correct 24V and 0V terminals. This is where you should hear a loud pop meaning winding selector engaged. From here you can measure high resistance and the terminals that were open before should give a reading while low resistance terminals should be open. When there is a constant 24V being supplied and the winding selector is not engaging many times is caused by a failure within Spindle drive.
For step by step video instruction follow the link to our YouTube video on how to test a winding selector. Just remember to have a circuit diagram on hand of your specific Winding Selector as terminal locations may be different.