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Performing Magic with TECO L510 VFD

fileophile

Plastic
Joined
Mar 16, 2019
I'm wiring up the VFC controls for a Bridgeport mill. I discovered a new old stock Furnas 3-pushbutton remote panel I'd love to use because it is small and fits nicely on the left side of the head. The 3 pushbuttons are labeled FOR, REV, and STOP. I wired it up per the TECO manual 3-wire system and it all works great -- except that the REV pushbutton is a momentary NO switch so when you press REV it does work to put the mill in reverse, but only if you are holding down that pushbutton. As soon as you release it the VFD decels and returns to FOR motion.

I know I can hack and slash the REV momentary NO switch inside the Furnas enclosure and replace it with a toggle switch. But I'm hoping there is a more elegant way. I have seen electronics that can turn the behavior of a NO momentary switch into the behavior of a latched 2-position switch. I think this capability very well might be already built in to the TECO L510 VFD. Does anyone know if it is?

I'm thinking along the lines of setting a VFD parameter so that the VFD monitors the S3 control circuit. Whenever it senses a momentary change (open to closed) to reverses the motor direction and keeps it reversed until it senses another open to closed state change.

Do I have to use a 2-position switch for FOR-REV or can a momentary switch be made to work?
 
Momentary switches are intended to work with things like motor starters that can have a "seal-in" contact that keeps the coil energized after you let go of the button. The standard setup for a VFD is for maintained control signals. So one way you could do it is to add two relays, each controlled by the Fwd/Rev buttons with their own seal-in contacts, then a second set of contacts wired to the VFD inputs. So power to the relays would go through the Stop button, to the Fwd and Rev buttons, to the coils of the relays, then one set of contacts of each relay is wired in parallel with the corresponding push button and a second set of contacts is wired to the VFD input. For Fwd, you press the Fwd button, it energizes the relay coil, then the seal-in contact closes around the push button and keeps the coil energized. Hitting the Stop button drops out the coil.

In some VFDs, they give you the option to have momentary contact closures (called "3 wire control") on the inputs, but it doesn't appear to be an option on the L510
 
In some VFDs, they give you the option to have momentary contact closures (called "3 wire control") on the inputs, but it doesn't appear to be an option on the L510

The L510 does allow 3-wire -- in fact that is how I have it wired up now. Every control in the control box is a momentary pushbutton switch. I need to know if I can tell, through programming, the L510 to treat one of those momentary switches as a maintained switch.

There is a interesting-sounding parameter 03-09 "S1~S5 Input type selection NO & NC" which sounds like I can tell the VFD something about switches, but it doesn't appear to have an option for a maintained type switch.
 
Three wire control requires a maintained closed contact for one of the directions. I do not know of any of the L510 commands that will convert the reverse direction from a maintained to a momentary command. It is possible to use a latching relay for the momentary reverse and have the latch broken when you press the stop button (either by a second pole or through the run relay of the VFD). Alternative as mentioned, which is what I predominately use for lathes and mills is to use two latching relays for FOR/REV with momentary run commands for the direction. It allows one to power tap and reverse quickly.
 








 
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