Two GMFs and one VFD

[BobL]

Over the weekend I got a really good deal I could not refuse on another GMF 1HP 3P grinder and am now looking at putting my small multitool Linisher onto that grinder as well as making it variable speed.

One thing I did not want to do was fork out for yet another VFD
but
its proposed next door neighbor will be this identical grinder
http://www.woodworkforums.com/attachment.php?attachmentid=329134&stc=1

So I thought, why not use the same VFD with a suitable cross over 3P switch between the two grinders.
Now because of the some individuals who occasionally use my workshop I won't feel comfortable unless there is some sort of lock that prevents switching the cross over while the VFD is running a grinder.

I have in the past proposed using a manual cross over switch placed inside a box, the inside of which is only accessible when the output of the VFD is off.
I was thinking of using a simple 12V door door latching solenoid to lock the door, and the lock is activated by a DPDT switch with the other side activating the VFD.
VFD ON - door locked

Maybe there is some sort of 3P switch that does this already but I expect that it will be pretty ex..

Any other suggestions welcomed.

[GuzziJohn]

I have in the past proposed using a manual cross over switch placed inside a box, the inside of which is only accessible when the output of the VFD is off.
I was thinking of using a simple 12V door door latching solenoid to lock the door, and the lock is activated by a DPDT switch with the other side activating the VFD.
VFD ON - door locked

Maybe there is some sort of 3P switch that does this already but I expect that it will be pretty ex..

Any other suggestions welcomed.

If you have the changeover switch in a box you could put a micro switch on the door so when it is opened the drive is tripped.
That way the drive output power will be off before the motor connections are changed over.

Close door. Restart drive.

[Stustoys]

Hi Bob,

Do you coasting stop or braking?


Stuart

[BobL]

If you have the changeover switch in a box you could put a micro switch on the door so when it is opened the drive is tripped.
That way the drive output power will be off before the motor connections are changed over.

Close door. Restart drive.

I like it!

Yes I use coasting stop, decelerated stop undoes the wheels.

[Stustoys]

I like it!
Whats the vsd going to do if you just lift the latch and let it drop agian? I've not tried it on a huanyang.

What are your plans re start switch/switches?

Stuart

[BobL]

Whats the vsd going to do if you just lift the latch and let it drop agian? I've not tried it on a huanyang.
Same as flicking a remote on/off switch, I do that quite often on my DP.


What are your plans re start switch/switches?
Stuart


Just one of these - probably with the same REE magnet on the back so I can move the switch to the front of each grinder as required.

http://www.woodworkforums.com/attachment.php?attachmentid=350719&stc=1

[Stustoys]

Same a flicking a remote on/off switch, I do that quite often on my DP.


Well thats good, if I recall correctly the Teco doesn't take to well to that sort of thing.


Just one of these - probably with the same REE magnet on the back so I can move the switch to the front of each grinder as required.

Then you wont need my ummmm rather complicated setup then :p

Stuart

[BobL]

Well thats good, if I recall correctly the Teco doesn't take to well to that sort of thing.

With the HYs on my DP and WW lathe I used light weight small switches and with the reverse on the same switch
Because the switches are light weight I sometimes flipped the switch to off and through into reverse!
Doing this the VFD/motor goes though its normal deceleration stage and then starts the reverse acc stage.
Then I realise, hey its going in reverse so I go to turn it off and I end up pushing it into few again - no problem.
Eventually I realised I had to be a bit more careful when switching these machines.
That's why I have now gone for more positive acting switches but I'm now used to the lightweight switches and although it still happens occasionally it doesn't appear to have harmed them


Then you wont need my ummmm rather complicated setup then :p
Stuart

Still wouldn't mind hearing it - could be useful somewhere else?

[Stustoys]

Doing this the VFD/motor goes though its normal deceleration stage and then starts the reverse acc stage.

Yes, but doesn't sound like you're using coasting stop.


Still wouldn't mind hear it - could be useful somewhere else?

Knock yourself out ;)
There isn't as much detail in the thread as I thought.
To be honest I've forgotten exactly how its wired. The switch uses a 4th pole to switch control of the VSD from one machine to the other.
I think there is something thing in the wiring to stop the machines controls latching on(or maybe they wont turn on at all) unless the controls are plugged into the vsd enclosure.
http://www.woodworkforums.com/showthread.php?t=129337&highlight=enclosure

[BobL]

Yes, but doesn't sound like you're using coasting stop.

Ah - you mean am I toggling back and forth on a machine with a coasting stop.
I haven't tried that - the machines with a coasting stop are 2 grinders and the BS.
I will try it out and report back.



Knock yourself out ;)
There isn't as much detail in the thread as I thought.
To be honest I've forgotten exactly how its wired. The switch uses a 4th pole to switch control of the VSD from one machine to the other.
I think there is something thing in the wiring to stop the machines controls latching on(or maybe they wont turn on at all) unless the controls are plugged into the vsd enclosure.
http://www.woodworkforums.com/showthread.php?t=129337&highlight=enclosure

It's way past my bedtime and I have the flu so I will look through that thread tomorrow.

[RayG]

If you want a positive interlock, you can get 3phase motor contactors that have mechanical interlocks, when one is energized the other is locked out.

Then you can wire the on/off switch at each grinder to pull in the appropriate contactor, no other changes required.

[BobL]

Knock yourself out ;)
There isn't as much detail in the thread as I thought.
To be honest I've forgotten exactly how its wired. The switch uses a 4th pole to switch control of the VSD from one machine to the other.
I think there is something thing in the wiring to stop the machines controls latching on(or maybe they wont turn on at all) unless the controls are plugged into the vsd enclosure.
http://www.woodworkforums.com/showthread.php?t=129337&highlight=enclosure

Ah yes I remember that thread. My requirements are almost trivial compared to yours because the two machines are identical so only one set of controls are needed.

[eskimo]

If you want a positive interlock, you can get 3phase motor contactors that have mechanical interlocks, when one is energized the other is locked out.

Then you can wire the on/off switch at each grinder to pull in the appropriate contactor, no other changes required.

Cannot Electrical interlocks do same?...ie isnt mechanical just a sureity to electrical

[BobL]

Ah - you mean am I toggling back and forth on a machine with a coasting stop.
I haven't tried that - the machines with a coasting stop are 2 grinders and the BS.
I will try it out and report back.

I did that - no problems, it resumes its acceleration from whatever RPM it happens to be doing.

[BRADFORD]

Hi Bob,
If you connect the VFD output to the line side of a contactor on each grinder (connected in parallel) and then electrically interlock the contactors so only one can operate at a time, you are all sorted, no need for a changeover switch.
When grinder one is running, grinder two cannot be started and vice visa.
If you don't have contactors with the required spare contacts, you could probably add relays to achieve the desired result.
When I do things like that I tend to use whatever I've got about the place, so sometimes it can end up a bit unnecessarily complicated.

[BobL]

Hi Bob,
If you connect the VFD output to the line side of a contactor on each grinder (connected in parallel) and then electrically interlock the contactors so only one can operate at a time, you are all sorted, no need for a changeover switch.
When grinder one is running, grinder two cannot be started and vice visa.
If you don't have contactors with the required spare contacts, you could probably add relays to achieve the desired result.

Yep I understand that setup and have considered it but that only fixes half the problem , that of making sure that only one of the grinders are connected to the VFD.
The other problem, which is just as importan,t is that of someone "breaking an ON contactor while the VFD/Motor are running".
This is why it's always better to fit VFDs with no switchgear in between the motor and the VFD.
We could put the contactors inside a box the door to which can only be opened when the VFD is off so now we are back to square one.


When I do things like that I tend to use whatever I've got about the place, so sometimes it can end up a bit unnecessarily complicated.
Yep I know what you mean, and that is why I'm looking at a simple change over switch and a micro switch on th e i.e. I have several of these at hand and ready to go.

[BobL]

Something I have thought about is the 3P crossover switch I'm thinking of using has zero (0) position and then 2 (1 & 2) contact positions.

This means there is a danger that the VFD could be set to run with the Cross over set at the 0 position i.e. VFD not connected to anything.

Fortunately the Crossover has 4 contacts so one of these can be wired up in series with the VFD remote switch.
So if that contact is not at 1 or 2 the VFD wont start.

Any other ideas?

Thanks

[Stustoys]

The other problem, which is just as importan,t is that of someone "breaking an ON contactor while the VFD/Motor are running".

Part of the theory behind my 4 pole switch* is that the front pole(VSD control) will open first(I use coasting stop). If you change to three wire control and momentary switches the VSD wont restart until the start button is pressed again.**
I think that will sort out your problem unless they hold their finger on the start button while changing the 4 pole switch.........If you think thats likely you could add at 5th pole at the back...... or hit them over the knuckles.

Also if you're going to use some sort of interlock or parallel contactors you could likely make use of the VSDs internal relay which can be set to close(or open) when the VSD has output on(it can also be set to do many other things but I doubt they will be useful in this case)

Stuart



Ah yes I remember that thread. My requirements are almost trivial compared to yours
Yes the price of VSD has past that setup by really... still it seemed like a good idea at the time :D

*its two throw with center off.

** once you've done that, may as well have a start button for each grinder?

[BobL]

OK I have changed my mind about the locked door because the 4 pole 2 position 3P switch looks like it might so what I want without locking it behind a door.

Heres the pseudo schematic.
When the X-over switch is turned the NVS is series will drop out which in turn will drop out the 240V relay and turn off the VFD
It will also stay off until the NVD is triggered.
The big question is will the "turning off" be quick enough for the VFD?

http://www.woodworkforums.com/attachment.php?attachmentid=350955&stc=1

[eskimo]

Adding timers to the circuit?

[Stustoys]

The big question is will the "turning off" be quick enough for the VFD?

My guess would be "No"

Why not just run the VSD control through the 4 pole switch in series with the 240V relay? (is it so you can stay with two wire control?)
Stuart

[Michael G]

What about the trick that they do for large industrial cabinets - having the handle to open the box that turns off the power to the VFD (supply side) when turned. Once the box is open, have a change over switch (grinder A or grinder B), but nothing will run before the cabinet is closed. Still use your pendant to turn the VFD on and off.

Michael

[BobL]

What about the trick that they do for large industrial cabinets - having the handle to open the box that turns off the power to the VFD (supply side) when turned. Once the box is open, have a change over switch (grinder A or grinder B), but nothing will run before the cabinet is closed. Still use your pendant to turn the VFD on and off.

Michael

That was what I had in the first post

[BobL]

Adding timers to the circuit?

yeah but delaying the 3P is not gunna be easy, perhaps a negative timer to turn the VFD off before I need to.

[BobL]

My guess would be "No"

Why not just run the VSD control through the 4 pole switch in series with the 240V relay? (is it so you can stay with two wire control?)
Stuart

Err that's what I thought I had?

[Stustoys]

I mean in series with the switched wires of the 240V relay, the VSD controls (but if you stay two wire the vsd will restart, so that would be no good)

The reasons I say 'no' is that I think 240VAC will arch longer than 12VDC, then you have how ever long the nvs takes to cut power to the relay and how long before the relay contacts open? (I need a recording CRO so I can test some of my thoeries ;)
If you want to stay with two wire I think you're better off having a cover over a 3 pole switch with a micro switch wired as the 4th pole is now, that would give you the delay you're after.

Stuart

[Michael G]

That was what I had in the first post

Sorry - the first post sounded like you were going to make something up. I was thinking of something off the shelf along the lines of

http://zjbeny.en.alibaba.com/product/1340891992-219974068/DC_Solar_isolator_switch_1000V_DC_TUV_SAA_CE_RoHS_certified_DIN_Rail_Mounting_Long_Handle.html

We have some at work where the rod on the handle physically keys into the switch so that the door can only be opened when the power is off.

Michael

[Stustoys]

Also it doesn't have to be a cover. a spring loaded pin that has to be held back to allow the switch to be turned would do.....must be a 1000 different ways to do it. Anything so there are two actions.

Stuart

[BobL]

OK I did the microswitch on the covered box method.

The 3P Xover switch extends thru into another box joined to the box with the transparent cover on it.

The 3P XO switch (from the 2 speed llinisher I converted to 240V 3P +VFD) has a ZERO position (i.e. VFD NOT connected to either grinder) so the switch could in theory be moved to the zero position and the XO box door closed, BUT the 4th contact on the XO itself will be in series with the XO door micro switch (from an old x-ray machine) so the VFD wont start unless;
- Xover switch is in position 1 or 2
- door to switch is closed
- NVS is finally pushed

http://www.woodworkforums.com/attachment.php?attachmentid=351104&stc=1

This is effectively what the circuit will be
http://www.woodworkforums.com/attachment.php?attachmentid=351105&stc=1

Still a fair bit of work to do on the rest of the circuit so there won't be much more to see for a few days.

[Michael G]

With my "take no prisoners" attitude to electrons. I would have done it like this -

351107

A No Volt Switch could be added but the VFDs that I have can do that anyway I think. The door switch will just be a power interuption.

Michael

[BobL]

With my "take no prisoners" attitude to electrons. I would have done it like this -

351107

A No Volt Switch could be added but the VFDs that I have can do that anyway I think. The door switch will just be a power interuption.

Michael

You've "lost one prisoner" with that circuit, and maybe it's not all that VFD or user friendly for my situation.

The "prisoner" is the zero XO switch position. - with your circuit someone could accidentally set the XO to zero - i.e. no grinder connected, close the door and start the VFD. The simplest way around that is to put Connection 4 on the XO in series with the door. I have thought of all these methods but have not gone that way because of the following - possibly splitting hairs a bit on some of these things but that's just me.

From the way I use the existing grinders there will be a fair bit of switching between the two. I don't like repeatedly powering VFDs up and down unnecessarily and as they take time to power up and down, the more I do it the longer they seem to take.:D Usually I turn the VFDs on as I need them and only turn them off if there is little likelihood of me using that machine again that session. The others on oft used machines like grinders, drill press etc stay on and get turned off at the end of the session.

In this specific instance the VFD is going to be on a steel post behind and above the two grinders, so no reaching over the grinders to control the VFD. This means it need a remote control anyway so an external on/off switch and speed control. I figured putting the door switch into that circuit saves the power cycling of the VFD and the extra NVS in the control circuit is my attempt at B&B.

Any large (preferably mushroom type) push button switch has to be a better emergency switch than relying on the little off switches used on most VFDs. Two of the machines in my shed that have no remote switches are the Hercus lathe and the linisher. I don't know how many times I have thought I have pushed the off switches on those and have not managed to turn the VFDs off. On Cheap VFDs I reckon the little pads, or at least the plastic on top of the switches are eventually gonna wear through.

[BobL]

I did a bit more work on the shared VFD across 2 grinders over the last few days and got it to the point where I could start assembling things this morning.

I decided to install the grinders on my tri-grinder stand, so step one was to add a swivel base for the VFD in the centre and on top of the existing stand
The white washer is teflon
http://www.woodworkforums.com/attachment.php?attachmentid=351682&stc=1

Then a length of 40 x 40 x 2.5 SHS slides over the top and is held in position with the screw knob.
This setup allows the stand to be rotated to be in front of the required grinder if required.
http://www.woodworkforums.com/attachment.php?attachmentid=351681&stc=1

VFD, cross over switch and other controls bolted onto a piece of ally plate which is bolted onto the central post.
http://www.woodworkforums.com/attachment.php?attachmentid=351680&stc=1

Here is close up of the controls.
XO is where the Xover switch is supposed to be
S1 is the main power switch - also acts as a safety switch
S2 is in series with the door switch in the XO switch box, the zero position in the XO switch, and a relay under S2.
When all 4 of these are closed S3 becomes available to start/stop the VFD
S4 is just the speed pot.
http://www.woodworkforums.com/attachment.php?attachmentid=351679&stc=1

The X0 switch was an absolute bear to wire up because the plastic boxes I used to house the switch in were a tad too small to hold 3 x 3 phase cables plus a control cable for the door switch so everything had to be squeezed in rather too tight for my liking.

Before I turned everything on I checked the continuity of everything and it was at this point I noticed the contact resistance of the XO switch was all over the place.
Cleaned with contact cleaner several tines - no change.

Then I made the fatal mistake of opening up the switch and when I finally had it apart I realised the permutations of reassembly was going to be very tricky AND the springs (there are around 20 of them) were going to be bastards to refit.

http://www.woodworkforums.com/attachment.php?attachmentid=351678&stc=1
My level of embarrassment eased when I checked out the contacts and found that they are pretty corroded/pitted anyway so I will ditch this switch and look for a replacement.

What an out and out PITA - I reconnected one of the grinders up to the VFD to least have that one available.

Now the VFD wouldn't work at all in remote mode. After lots of futzing, changing parameters etc, I remembered that the jumper that switches between the VFD pot and the external pot had been a bear to remove - when I looked closely at it I could see what looked like some (hot) glue residue on it and also on the pins on the VFD - I reckon it had been glued in place. So I scraped the glue of the pins and used a new jumper and all was then working.

This has been a lot of trouble and I wonder if it has really been worth it.
I guess I have made some progress because the rest of the controls are now fully tested and they work well.

I was thinking of getting a 3 way cross over so all 3 of the grinders on the trigrinder stand could eventually be run off the single VFD.

[BRADFORD]

This has been a lot of trouble and I wonder if it has really been worth it.

It was a challenge, and if you are anything like me you can't let a challenge go unbeaten.



I was thinking of getting a 3 way cross over so all 3 of the grinders on the trigrinder stand could eventually be run off the single VFD.


Hell Bob you're a terror for punishment

[DaveTTC]

Wow Bob, wish you lived around the corner from me. Id really enjoy oicking your brain

Dave TTC
Turning Wood Into Art

[BobL]

Wow Bob, wish you lived around the corner from me. Id really enjoy oicking your brain

Dave TTC
Turning Wood Into Art


You will have to do it remotely Dave. :D

[DaveTTC]

Ok a few questions. And yes much of this (now that i have read the entire thread) goes way over my head.

1) does your lazy Susan have a lock so which ever grinder you are using does not move while in use

2) can your vfd be left 'switched on' while not connected to or powering anything?

3) if yes to the above can you switch it to a grinder without having to turn it off first?

4) can you just disconect your grinder from the vfd (while running) withiut any issue.

I have some thoughts as to various solutions pending the answers above. You may have answered some of these already but i have faiked to understand the issues.

Also what is a bs? You referred to a bs in one of your posts.

Dave TTC
Turning Wood Into Art

[BobL]

Ok a few questions. And yes much of this (now that i have read the entire thread) goes way over my head.

1) does your lazy Susan have a lock so which ever grinder you are using does not move while in use
Yes it does - look here http://www.woodworkforums.com/showthread.php?t=133650&p=1484716#post1484716


2) can your vfd be left 'switched on' while not connected to or powering anything?
The sequence is turn on mains switch to VFD and wait about ~3 seconds for it to boot up.
This wait time is small but quite irritating so I tend to e.g. turn the VFD on when I need to use each machine and then leave the VFD on for the rest of the day as they consume very little power.
Each machine motor is then started via the switches on the VFD, or remote wired switches.
Like computers, power the VFDs constantly up and down is not good for them,
Most VFDs have rows of little terminals that allow for wired remote switches t turn the motor on/off./fwd/backward/jog and connections for multiple speeds etc


3) if yes to the above can you switch it to a grinder without having to turn it off first?
Yes - I could (except my cross over switch is buggered and I've ordered a new one)


4) can you just disconect your grinder from the vfd (while running) withiut any issue.
Yes provided the motor is not running.otherwise this will damage the VFD.


I have some thoughts as to various solutions pending the answers above. You may have answered some of these already but i have faiked to understand the
You're thinking one VFD and connect it up to multiple machines.
Sorry - no good.

Some of your motors will be 1440 and others will be 2850 rpm and some might be something else. Some will draw high currents others will draw low currents, some machines can do high speed others cannot.
Each VFD needs to be programmed with all this info so when you switch between different machines/motors all this info needed to be entered again.
On fancier VFDs you can pre-program a number of setups and recall these specific programs later - sounds good, real good, BUT it is VERY EASY TO STUFF IT UP because the VFD cannot check that it really is connected to the motor for that program.
Believe me you do not want to be flipping between programs and waiting for the parameters to reset etc when all you want to do is touch up a drill bit.
You just want to turn it on and go.

That is why dedicated VFDs are a lot more user friendly. Like I said in my previous post, the two identical grinders I'm running off the one VFD should be a dead simple operation but setting up all the interlocks and switches makes it an out and out PITA even for someone like me where I enjoy farting around with these things just to see if I can get it working.


Also what is a bs? You referred to a bs in one of your posts.
Bands saw - this onehttp://www.woodworkforums.com/showthread.php?t=195900

[DaveTTC]

Ok this is an idea for your set up. Ill try dot points. Let me know if it is viable or I'm on the right track.

You have vfd contacts near the arm of your grinder support, posibbly brushes.

The grinders have corresponding contacts that only contact when in the locked and user position.

The grinder is switched by its own switch off and on when locked in position.

There could be some kind of magnetic lock pin so that while under power or rotating the grinder can not be swung around.

Contacts on grinders could be a disk which make contact with brushes like in a motor. A continuous segemted disk all the way round your centre column which is only conductive in the range of the device in the locked position.

If your centre column wad like a goose neck it would bring the controls within range of use without need for remotes. Other option would be to have it under thenarms but set forward so in reachable spot.

Im not an electrician so dont know how viable these ideas are but thiught id put it out there

Dave TTC
Turning Wood Into Art

[BobL]

Ok this is an idea for your set up. Ill try dot points. Let me know if it is viable or I'm on the right track.
You have vfd contacts near the arm of your grinder support, posibbly brushes.
The grinders have corresponding contacts that only contact when in the locked and user position.
The grinder is switched by its own switch off and on when locked in position.
There could be some kind of magnetic lock pin so that while under power or rotating the grinder can not be swung around.
Contacts on grinders could be a disk which make contact with brushes like in a motor. A continuous segemted disk all the way round your centre column which is only conductive in the range of the device in the locked position..

It would take too long to go into specifics about all the problems with these suggestions but here are a couple of points.

The assumption that there is a specific "user" position that requires each grinder to be moved to that position is not the case . Moving the turntable is a bit of a pain and having to move the turntable to make electrical contact would be an extra nuisance. Mostly the turntable stays in one place with the two grinders I'm most likely to use facing outwards. The two most commonly used are the one with the CBN wheel and the grinder with the finisher on it. The grinder with the wire wheel and the coarse grit wheel usually sit at the back up against the wall. I move the turn table maybe only or twice a day. I also have a floor standing 10" pedestal grinder that runs off its own VFD

The other problem is the use of wipers or brushes. In VFD manuals they usually state there should be no contacts/wipers or switches between the VFD and the motor - there's just too much of a chance that one of those connections doesn't connect so well or at slightly different times and that could be the end of the VFD. I'm using one simple crossover switch protected by two interlocks and that is about as far as I'm prepared to go.

With regards location of switches at grinder level or below the grinder, these very dirty places, lots of grit and metal dust - the best place for switches and the VFD is definitely above the grinder.

[DaveTTC]

Thankyou for the education. It has been interesting. I have much to learn

Dave TTC
Turning Wood Into Art

[BobL]

Thankyou for the education. It has been interesting.
No worries

I have much to learn
I think we all have much to learn :)

[Stustoys]

I I'm using one simple crossover switch protected by two interlocks and that is about as far as I'm prepared to go.
Don't worry to much Bob, I've run a few of my VSD's with nothing corrected to the output. Vsd's didnt seem to care(or even notice), and no smoke was released.

How long and how often you can get away with this sort of behavior I have no idea :D

Stuart

[BobL]

Don't worry to much Bob, I've run a few of my VSD's with nothing corrected to the output. Vsd's didnt seem to care(or even notice), and no smoke was released.

How long and how often you can get away with this sort of behavior I have no idea :D

Stuart

Yeah I've tried to start one a couple of times without the VFD being connected and it wouldn't start. Another time I started one where one of the phase connections on the motor wasn't tight and it got part way into the acceleration cycle and then shut down. I've never disconnected one while it was under load though.

[Stustoys]

I've never disconnected one while it was under load though.
Oh yes, I have no plans to try that. I haven't even been game to try switching the coolant pump on/off with the main motor running, even thought the guy at Drives Direct says it will be fine.

Stuart

[BobL]

The new cross over switch arrived and has been installed.

Nothing much new to see really.
Here are the two GMFs running alternately off the one VFD with cross-over switch above.
I need to tidy up the cables a bit with some cable ties but there has to be some slack in the cables as the grinders can be moved back and forth and rotated on the tri-grinder arms.

http://www.woodworkforums.com/attachment.php?attachmentid=353327&stc=1

The new switch is smaller than the old one and I had to chop the switch box around to fit the the old one so there is a bit of a gap around the new one)
The contact resistance of the new switch is all less than 0.2Ω, the old one was anywhere between 0.2 and 20 Ω.
http://www.woodworkforums.com/attachment.php?attachmentid=353326&stc=1

How does it work - well read on.

All the interlocks work to turn the VFD ON-OFF switch as designed

BUT (near in mind the VFD is set to a coasting stop)

While testing, with the VFD running a grinder I opened the door to the X-over switch and yes the VFD did switch off and the grinder started to coast to a stop but I then immediately flipped the X-over switch door (now the VFD is connected to the other grinder and it started turning? I didn't wait to see what happened because I immediately cut the power to the VFD. So it's like there is some residual Potential/current in the VFD? Remember the VFD on-off switch had been switched into the OFF position.

I'm not that worried about it because I will wait unit the running grinder has stopped before switching but other folks who want to power more than one machine might run into some problems with this so this is why I thought it was worth posting.

[EDIT] It turns out I did not have the VFD programmed for a coasting stop, I had it on a 20s deceleration, so with a coasting stop it does not start the other grinder. However, the situation still applies if you have a decelerating stop.

[Stustoys]

[EDIT] It turns out I did not have the VFD programmed for a coasting stop, I had it on a 20s deceleration,

And yet no smoke was released!
I wonder just how much of this sort of thing these VSDs will really put up with.

Stuart

[BobL]

And yet no smoke was released!
I wonder just how much of this sort of thing these VSDs will really put up with.

Stuart

Just to prove the first time was not a fluke I did it twice more AND only then I realised I probably had not switched that VFD to coasting stop.
Still no smoke :)

I really gave those interlocks a bit of a work out.

[BobL]

I spent most of yesterday rearranging the bench grinder attachments, which is really just another version of rearranging the screwdrivers, just a lot slower.

Now the 2 variable speed GMFs have the following
One the gold coloured GMF there is the
- thin kerf cutting disc saw and a
- green wheel

On the green GMF there is the
- CBN wheel and a
- multitool linisher

The linisher was on a 1Phase Abbot and Ashby but I wanted it mounted onto one of the variable speed grinders.
The mounting was a bit of a pig because two bearing locating screw heads interfere with the multitool mounting and of course the GMF has longer shafts so I can't attach the outer multitool sanding disc base because the shaft pokes through the space. To get around this I could pack out the multitool base but 'm just leaving this because I don't use the disc anyway as I have a 12" disc on another.

The Abbot and Ashby (which my brother gave me a few years ago sans guards and flanges) is a grunt little grinder and now has a new 8" Scotchbrite wheel and a wire wheel. Mounting the wire wheel needed new flanges made as the residual GMF flanges are too thick for the A&A shorter shaft.

The variable speed Atkins pedestal grinder will become an actual grinder and the old 10" can be disposed off - hey I'm actually getting rid of something from my shed :)

During the process I have been using the cross over switch between the two GMFs and in general it works very well HOWEVER, one thing I discovered was.

Grinder A running, turn of VFD, quickly switch cross over to grinder B - ALL good (note grinder A still coasting - from full speed it will coast for several minutes)
If I now switch back to grinder A (still coasting at relatively high speed) the VFD of course wants to start/run under a controlled ramp so it rapidly decelerates Grinder A and this can loosen the wheels :oo:

All part of a learning curve and hopefully useful for other folks that want to do this,

[Stustoys]

If I now switch back to grinder A (still coasting at relatively high speed) the VFD of course wants to start/run under a controlled ramp so it rapidly decelerates Grinder A and this can loosen the wheels :oo:


Have you tried using PD025=1?(including pd032,33 and 34)

Stuart

[BobL]

Have you tried using PD025=1?(including pd032,33 and 34)

Stuart

No I haven't but reading the manual suggests it is a good idea.
Even if you have one VFD and one high inertia load machine.

Any idea what reasonable settings would be for PD32-34 - go with the factory settings for a first up?

[Stustoys]

Any idea what reasonable settings would be for PD32-34 - go with the factory settings for a first up?

Sorry Bob cant be any help there. To long ago and it was only a "play" I'm not sure I came to a conclusion. Good luck :D

Stuart