VFD control wiring issues

[Lee Alkureishi]

Hi all,

I acquired a new old stock VFD recently, and have everything wired up. But, I'm having a few difficulties.

Make/Model: Dana / Warner Electric Nextdrive, model SC4202, 2HP, 1ph or 3ph in, 3ph out

I'm attempting to wire some controls for easier control. I have a forward-off-reverse switch, and a 10k pot. These controls are the same components as I've used in my other VFD setup.

My connections are as follows:

Switch
right (forward) terminal = terminal 9 (run)
centre terminal = terminal 6 (digital common)
left (reverse) terminal = terminal 11 (reverse)

10k Potentiometer
Right terminal = terminal 4 (+10V supply)
Wiper (centre) = terminal 3 (VIN - Spd Ref)
Left terminal = terminal 2 (Analog common)

In addition, there are 2 notes in the manual:

Note 1: Connection between terminals 6 (digital common) and 7 (external trip) is required for any drive operation. When the drive is running, opening this connection results in a drive fault (External trip)
Note 2: Connection between terminals 6 (digital common) and 8 (stop) is also required to run the drive. Install any stop interlocks that are required. Opening the stop circuit when running will cause the drive to ramp to a stop.

To address these, I connected an SPST on-off switch, with the following connections:
Left terminal = digital common AND external trip (Giving the required electrical connection between these two terminals - see note 1 above. I think this might be wrong, but I'm not sure how it should be wired instead)
Right terminal = stop

When I switch on, I can tell the VFD to start the motor on the keypad, but the forward-off-reverse switch does not work (I have changed the setting in the VFD to tell it to accept a control signal from other than the keypad). The potentiometer does vary the speed, but it goes through the entire range from 0rpm to 1800rpm within about 1/10 of a turn.

So, a few questions for this electrical numptie:

1) I'd prefer to lose the SPST on-off switch altogether, but I'm not sure how to do that while satisfying notes 1 and 2 above?
2) Can anyone suggest what's wrong with my wiring? I'm guessing that something with digital common, external trip and stop is preventing the on-off-on switch from working properly.
3) Can anyone suggest how to fix the potentiometer speed control, to use a full turn of the dial?

Thanks in advance,

Lee

[jack forsberg]

you need a 3 position maintain switch for froward on and reverse on operation. and all you do is loop a wire from 7 and 8 to 6 at the VFD to close those contacts if you do not want there function. It goes with out saying you have set the VFD prompt to external control.


For the Pot what is the VFD Hz range set to? a large range of above 120 to 0 hz is to much range for sensitive speed control. You can set the lower range too.

[Lee Alkureishi]

Hi Jack,

Thanks for the suggestions. The switch I'm using is correct, a forward-off-reverse maintained switch which I have successfully wired to my other vfd.

I'll try loping the wire as you suggested, thanks.

For the pot, the hertz range is set to 0-60Hz on the VFD.

Thanks again,

Lee

[Anthony Whitesell]

Make/Model: Dana / Warner Electric Nextdrive, model SC4202, 2HP, 1ph or 3ph in, 3ph out

I'm attempting to wire some controls for easier control. I have a forward-off-reverse switch, and a 10k pot. These controls are the same components as I've used in my other VFD setup.

My connections are as follows:

Switch
right (forward) terminal = terminal 9 (run)
centre terminal = terminal 6 (digital common)
left (reverse) terminal = terminal 11 (reverse)

10k Potentiometer
Right terminal = terminal 4 (+10V supply)
Wiper (centre) = terminal 3 (VIN - Spd Ref)
Left terminal = terminal 2 (Analog common)

In addition, there are 2 notes in the manual:

Note 1: Connection between terminals 6 (digital common) and 7 (external trip) is required for any drive operation. When the drive is running, opening this connection results in a drive fault (External trip)
Note 2: Connection between terminals 6 (digital common) and 8 (stop) is also required to run the drive. Install any stop interlocks that are required. Opening the stop circuit when running will cause the drive to ramp to a stop.

To address these, I connected an SPST on-off switch, with the following connections:
Left terminal = digital common AND external trip (Giving the required electrical connection between these two terminals - see note 1 above. I think this might be wrong, but I'm not sure how it should be wired instead)
Right terminal = stop

When I switch on, I can tell the VFD to start the motor on the keypad, but the forward-off-reverse switch does not work (I have changed the setting in the VFD to tell it to accept a control signal from other than the keypad). The potentiometer does vary the speed, but it goes through the entire range from 0rpm to 1800rpm within about 1/10 of a turn.

So, a few questions for this electrical numptie:

1) I'd prefer to lose the SPST on-off switch altogether, but I'm not sure how to do that while satisfying notes 1 and 2 above?
2) Can anyone suggest what's wrong with my wiring? I'm guessing that something with digital common, external trip and stop is preventing the on-off-on switch from working properly.
3) Can anyone suggest how to fix the potentiometer speed control, to use a full turn of the dial?

Thanks in advance,

Lee

Disclaimer: I did not look for a manual for your VFD. Just based on your post. I will update if I am able to find one online.


The purpose of the external trip is to be able to wire in a 'run fault detector' and stop the VFD, such as device to detect the lack rotation, flow, etc. The stop circuit is just that, open to stop the VFD. I'm not sure you can lose the SPST switch without a different set of contacts on the fwd-off-rev switch.

It appears we know the SPST switch works. I would temporarily swap out the fwd-off-rev switch for another SPST connected to just fwd, or just remove the switch and use a piece of wire to jump the terminals a necessary.

Do you have the configuration in the VFD set to free running mode? The VFD may be trying to match the analog speed input to a speed reference input.

I have a VFD with the exact same specs as yours but a different manufacturer. It works completely differently. For one thing, there is no stop input. So unless you have used this VFD elsewhere, I wouldn't assume that two VFDs by different manufacturers work the same.

[Lee Alkureishi]

Hi all,

thanks for the input.

I made some progress today - not all of it good!

I removed the SPST on-off switch, and instead bridged from "Digital Common" to both "Ext Trip" and "Stop" with wire. I then looked at the VFD settings again - I had set "Setpt Src" to "analog", but didn't set "CmdSrc" to "terminal". I did that, and the SPDT on-off-on switch now works - but not as expected. If I flip the switch to the left (reverse) position, the motor runs forward. Flipping it back to centre does not stop the motor. Flipping it to the right (forward) position reverses the rotation of the motor. Flipping it back to centre from there now changes direction again (to forward). The only way to stop the motor is to hit "stop" on the keypad.

I thought maybe I had wired the switch in wrong, so I flipped the reverse (terminal 11) and digital common (terminal 6) connections to the switch as a test. It functioned exactly the same. I'm now a little unclear as to what's going on.

For now, I took the switch out completely (disconnected the three wires going to DCM, RUN and REV). Now, when I switch on the VFD (flipping the mains switch), the motor starts running immediately. I can stop it from the keypad, and start again from the keypad. I think this is related to the stop terminal being bridged with a jumper - would it be possible to use a DPDT (on-off-on) switch here instead? If anyone can give any pointers on how to wire this, it'd be much appreciated!

The potentiometer still runs through the entire range within 1/8 of a turn. I've gone through all the settings in the VFD, and don't see any option to change the frequency range. The only settings are "Max Hz" which I have set to 60Hz, and min speed (18rpm) and max speed (1800rpm) I tried changing max speed to 3400rpm temporarily, but it just ran from 18rpm to 3400rpm in the same amount of dial turning. I don't see any option for free running mode. No idea! My next step will be to go through all the settings and list them here - maybe someone will spot the one I need to change!

Lee

[Anthony Whitesell]

Lee,

The Off position of the switch will need to open the STOP terminal. If you combined the fwd-off-rev switch with the SPST (a pushbutton would be even better than a toggle switch) wired the way you had it would probably work. The way it would operate is to move the switch to fwd (or rev), then to stop and toggle the SPST switch which would stop the motor, then rotate to rev (or fwd).

The better way to do it, would be to have a second set of contacts on the fwd-off-rev selector switch. The first set as you have them connected now and the second set will have stop set on the fwd and rev sides, and open in the center. This switch should work http://www.allelectronics.com/make-a...OSITION/1.html.

If you really like your fwd-off-rev switch (or don't like or have access to a switch as I listed) and if you have enough power to run a relay, you could install two DPST relays. One for forward and one for reverse. Each would close the stop and fwd or rev connection.


LEEVFD.jpg

[Lee Alkureishi]

Anthony,

Thanks again for your help, and the very clear explanations. I bought a DPDT switch yesterday, and will hopefully get it wired up this weekend. Will report my findings!

Lee

[Lee Alkureishi]

Ok, I'm getting close (slowly!). I wired up the DPDT switch as you suggested:

Upper row of contacts: reverse - digital common - run
Lower row of contacts: stop - digital common - stop

Now, when I flip the switch to the right, the motor starts. Great! Flip it back to centre, it switches off. All good so far!

But, when I flip the switch to the left, the motor doesnt run in reverse as expected. The indicator LED on the front of the VFD does switch to reverse, but the motor doesnt start. If I then switch back to centre, the indicator shows "forward", and switching to the right starts the motor in forward again.

Is this likely just the way this VFD works? In which case, I would need to separate the forward/reverse and on/off switches? Or is there a way to make it work with the on-off-on switch? If possible, I would like to keep the controls as similar to my other VFD as possible..

Thanks again for your help,

Lee