B
brandonmays
Guest
Been busy installing a AC Tech VFD on an older Bridgeport BOSS CNC mill. Got the drive mounted to the exterior of the magnetics cabinet, installed the speed control potentiometer on the mill’s main control panel and ran the wire, ran the motor leads in metallic seal-tite, and the ferrite toroid came in and was installed in the supply to the VFD. Since the VFD takes the place of both the reversing contactors and motor overload relay, I re-used one portion of the reversing contactor to be a supply disconnect, controlling it through the E-stop contactor, so the VFD is powered down when the E-stop is pushed in. That way it’s easy to remove the power from the VFD but still leave the machine controller on.
I have just one niggling little problem; not enough I/O. The AC Tech SMV comes with ONE set of dry contacts, ONE digital logic output, and ONE analog logic output, any of which can be configured to activate due to numerous user specified conditions. The problem is, I need two outputs. The dry contacts I understand, but the logic outputs are Greek to me.
The dry contacts I was going to use to control the Bijur lube pump. This mill, if left powered up, would form a puddle of way oil on the floor, so I had wired the Bijur pump through an extra set of contacts on the reversing contactors, so it only ran when the spindle is running; no spindle = no motion = no need for way lube. This way the mill could be left running into the night, and when it finished the lube pump automatically shut off, so I didn’t come in to find an oil slick in the morning. Now there is no reversing contactor, so I was going to use the dry contacts on the VFD.
But, I also need a way to stop table motion if the VFD faults and the spindle stops, since that would be a sure recipe for disaster if the spindle stopped but the table kept trying to run the program. In the former setup, the E-stop contactor was wired through an auxiliary contact on the motor overload relay. But that won’t work now, as that will power down the VFD. The old overload relay had a manual reset that the VFD lacks.
Lacking any other input available on the control, the best I can come up with is to interrupt a limit switch circuit, which will stop the program without loosing its place. The problem is, if I set this to be active when the spindle in not running, I can’t home the machine, set tools, etc. I need a different criteria for this output, only active when the VFD is in fault condition. So, I can’t use the dry contacts that have already been used.
Can anyone explain what sort of logic device I can use to read the digital logic output?
I have just one niggling little problem; not enough I/O. The AC Tech SMV comes with ONE set of dry contacts, ONE digital logic output, and ONE analog logic output, any of which can be configured to activate due to numerous user specified conditions. The problem is, I need two outputs. The dry contacts I understand, but the logic outputs are Greek to me.
The dry contacts I was going to use to control the Bijur lube pump. This mill, if left powered up, would form a puddle of way oil on the floor, so I had wired the Bijur pump through an extra set of contacts on the reversing contactors, so it only ran when the spindle is running; no spindle = no motion = no need for way lube. This way the mill could be left running into the night, and when it finished the lube pump automatically shut off, so I didn’t come in to find an oil slick in the morning. Now there is no reversing contactor, so I was going to use the dry contacts on the VFD.
But, I also need a way to stop table motion if the VFD faults and the spindle stops, since that would be a sure recipe for disaster if the spindle stopped but the table kept trying to run the program. In the former setup, the E-stop contactor was wired through an auxiliary contact on the motor overload relay. But that won’t work now, as that will power down the VFD. The old overload relay had a manual reset that the VFD lacks.
Lacking any other input available on the control, the best I can come up with is to interrupt a limit switch circuit, which will stop the program without loosing its place. The problem is, if I set this to be active when the spindle in not running, I can’t home the machine, set tools, etc. I need a different criteria for this output, only active when the VFD is in fault condition. So, I can’t use the dry contacts that have already been used.
Can anyone explain what sort of logic device I can use to read the digital logic output?
