[bit pusher]

Hi guys, I've got my belt drive setup and things very smooth and quiet at 60Hz using the AC bearings.
I'd like to get a few more RPMs out of it and push the VFD higher.
If I run at 80Hz things are still relatively quiet and vibration free, but I get into trouble when I try to stop the spindle.

The Mitsubishi FR-D700 shows an error indicating "Regenerative overvoltage trip during deceleration or stop". The spindle then crawls to a stop and I must press reset on the VFD to get control back.
This happens about 20% of the time.

What is the remedy for this?

The only change I've made to the VFD settings from the factory are to max frequency output with potientiometer at 5v (changed from 60 to 80). I left the base frequency settings all at 60Hz.
Do I need to make any further changes elsewhere in the VFD config?
Or should I slow the deceleration in Mach3 using motor tuning to slow the accel/decel of the spindle?

thanks in advance

[Al_The_Man]

Deceleration parameter rate is too short.
Al.

[bit pusher]

Deceleration parameter rate is too short.
Al.

I changed the mach3 settings for spindle in the motor tuning attempting to slow it down. I got it slowed down to a 5 second accel/decel and it still triggered the over-voltage-trip.

I read the manuals for an hour and found settings for decel time, but it was already set to 10s, and found another param which attempted to slow decel if initial OV was detected. That was set to on by IH or MachMotion. Neither of these settings resolved the problem.

The best I could manage was to disable the regenerative breaking completely and let the motor coast to a stop as soon as it detected forward run signal had gone low. Now I have a 6-second gradual slow down instead of the 1-second VFD assisted stop. Its a decent work around and a good trade off for the added speed, but I'd like to get regenerative braking working again.

If anyone knows which specific params I should change on VFD, or which settings I should change in Mach3, I'd greatly appreciate the advice!

[mactec54]

If anyone knows which specific params I should change on VFD, or which settings I should change in Mach3, I'd greatly appreciate the advice!

It's quite simple if you have the Manual, just look for the Deceleration Parameter if your manual does not look like what I have posted

Just adjust target # 8, Nothing in Mach 3 can control these VFD Settings/Parameters, It has a default of 5 sec, you most likely need around 10 or 12 sec, if you need you spindle to stop quickly, then you may need to fit a Braking Resistor

[Eldon_Joh]

Add a brake resistor if it can take one. 500 watts per hp should be more than enough. resistance equals volts squared divided by watts.

[bit pusher]

Thanks guys. I did try setting the deceleration time last night, I bumped it up to 15s (from 10s) but the parameter had no effect on the braking.
I think the existing braking resistor is the correct anser and the one I have (if there is one) may be insufficient for 80Hz -> 0Hz
Thus far I've only fiddled with software setting on the VFD and in Mach3. I received the mill's electrical cabinet ready to go as part of a turnkey setup from IH in 2013 and have not had to do any rework as it all ran great from the minute I turned it on. Tommy mentioned it was wired up by MachMotion. I'm a little disinclined to start taking things apart right now to upgrade the braking resistor, as I can live with the 6s decel/coasting time. I'll revisit this issue when I upgrade from mach3 + smooth-stepper to linuxcnc + mesa board sometime later this year.
Again, thanks for all of your advice.

[mactec54]

bit pusher

I think you have been play with the wrong settings, you don't have regenerative Braking without a external fitted Braking Resistor, so I think you have settings Parameters set wrong for the use of the built in internal Braking Resistor

15s is more than enough so this Parameter is not working, because you have activated, the Regenerative Parameters, & the VFD is by passing the Target # Pr8 setting

[bit pusher]

bit pusher

I think you have been play with the wrong settings, you don't have regenerative Braking without a external fitted Braking Resistor, so I think you have settings Parameters set wrong for the use of the built in internal Braking Resistor

15s is more than enough so this Parameter is not working, because you have activated, the Regenerative Parameters, & the VFD is by passing the Target # Pr8 setting

If I disable regen-braking completely, it will accept pr8 ?
I suppose I should disable the coast-to-stop on pr250 too

Time to dig through the manual to see exactly how to disable regen-braking...

[mactec54]

bit pusher

Coast & Regen will have to be not active,for the PR8 to work, you may have set other settings as well that are not needed

If you know what the basic settings are that you are using, you should do a Drive reset to the factory Default settings, & only set the first level of settings, which may only be 4 or 5 Parameters that need to be changed to suit you motor

[bit pusher]

bit pusher

Coast & Regen will have to be not active,for the PR8 to work, you may have set other settings as well that are not needed

If you know what the basic settings are that you are using, you should do a Drive reset to the factory Default settings, & only set the first level of settings, which may only be 4 or 5 Parameters that need to be changed to suit you motor

This is the first time I've made changes to the VFD, so I'm a little skittish about making alterations to IH / MachMotion's settings as they've got far more experience at it.
Is there anything that would be harmed by doing the reset (and of course re-doing the first few params as you stated)?

[mactec54]

bit pusher

I thought you had set the VFD yourself, you should get a list from MachMotion as to what Parameters they had set, then you can compare, to what you have set now,

No nothing can be harmed by doing a reset, but you should have what Parameter MachMotion have used, before you do a reset, or you may not be running at all, if you don't have what Parameters they have used for their system

They may have some Parameters that there control uses, so you need there list

[Al_The_Man]

I have used a few Mitsubishi VFD's but not the D700, but the ones I have used have a self tuning feature, (which most people don't seem to use?).
I imagine the D700 would?
I use that to get in the ball park and then tweek it a bit, I have got my XLO mill down to just a few seconds of braking.
Al.

[bit pusher]

bit pusher

I thought you had set the VFD yourself, you should get a list from MachMotion as to what Parameters they had set, then you can compare, to what you have set now,

No nothing can be harmed by doing a reset, but you should have what Parameter MachMotion have used, before you do a reset, or you may not be running at all, if you don't have what Parameters they have used for their system

They may have some Parameters that there control uses, so you need there list

Thus far my changes have been limited to param125 to 80Hz (this one controls max frequency at max analog input across the potentiometer).
I also set pr250 to 0 which enables the coast to stop after 0 seconds.
I'll email mach motion and see if I can get them to send me their default settings for th VFD.

[mactec54]

I have used a few Mitsubishi VFD's but not the D700, but the ones I have used have a self tuning feature, (which most people don't seem to use?).
I imagine the D700 would?

The D700 has not got the Auto Tune, seems they took that & a lot of other Parameters out of this Drive, & added some more complication that is not needed for normal use