Author Topic: 626 mill motor/inverter mods  (Read 772 times)

Offline John Rudd

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626 mill motor/inverter mods
« on: November 24, 2016, 10:42:48 AM »
Moving swiftly along to the next in this series of millmodding,I'm doing a 3 phase conversion using an inverter.
Pictures of the motor and inverter are already in the riser block thread so I wont show them again.
So after removing the original motor, the new one is bolted in place. its a direct swap, both are frame 90 size, so I wouldnt expect any issues here.

The motor was prewired with its supply cables, all I have to do is run some flexy trunk from it to the inverter...

More to follow, meanwhile the obligatory picture ot two. :zap:
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Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #1 on: December 14, 2016, 09:48:57 AM »
So,had a bit of a break from posting about this.....
Its all done, wired up, inverter programmed and away we go..

I mounted the inverter enclosure on the back of the mill, seemed to be the most logical place to put it..Out of harms way and close to supplies and motor.
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Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #2 on: December 14, 2016, 09:51:18 AM »
Now the most difficult part of this mod was deciding on where the controls were going to go :scratch:

I had already mounted them into a suitable box and after much agonising, I settled for just under the Y axis at the front on the knee....
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Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #3 on: December 14, 2016, 09:54:33 AM »
After trying out the controls and generally messing with the mill, I concluded that their location was justified.
I was going to try and combine the nvr switch with them but I could'tt get a box suitable to house the whole lot....Anyway it looks ok, just need a label now for the FWD-OFF-REV switch and speed pot..

See what you think?
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Offline russ57

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Re: 626 mill motor/inverter mods
« Reply #4 on: December 21, 2016, 07:11:36 AM »
Neat.  I need to do the same thing.  Do you have the nvr switch supplying the vfd?  When I tried that the standby current of the vfd wasn't enough to hold it on.
Russell

-russ


Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #5 on: December 21, 2016, 10:48:58 AM »
Russ,
The nvr is wired as supplied.
I removed the wiring going to the original motor.
The fed for the inverter is supplied by the terminals that fed the run winding of the original motor. The start winding wiring isnt used and the terminals are empty on the outgoing side.
The interlocks are still wired in, ergo, if I lift the belt cover lid, the motor stops as it would originally.

Not sure why the standby current would influence the operation of your nvr? :zap:
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Offline russ57

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Re: 626 mill motor/inverter mods
« Reply #6 on: January 01, 2017, 06:14:13 AM »
I assumed it needs a minimum current to hold the relay closed,  and the vfd when not powering the mill didn't draw that much.  Perhaps there are nvr's and nvr's...

-russ


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Re: 626 mill motor/inverter mods
« Reply #7 on: January 01, 2017, 12:02:55 PM »
Hi The NVR function should be wired into the control side of the in vertex not interrupt the supply side of the inverter, it can take a bit of figuring out but that is the correct way to do it. Phil

Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #8 on: January 01, 2017, 12:17:03 PM »
Phil,
Could you explain why this is please?

I've not read anything the documentation about having an nvr on the supply side....mcb yes....
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Re: 626 mill motor/inverter mods
« Reply #9 on: January 01, 2017, 04:27:02 PM »
Hi John
It's not a good idea to remove the supply from the inverter when it is in full flow as it were, if you say opened a guard on a stationary machine arguably no different to switching off at the wall.
However if the machine is under load removing the"drive" signal via the interlock switches rather than the contractor results in a controlled shutdown.
The set perimeters operate correctly i.e. Dynamic braking etc and the energy in the electronics is dissipated correctly
Hope this helps Phil

Offline russ57

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Re: 626 mill motor/inverter mods
« Reply #10 on: January 01, 2017, 07:49:48 PM »
Terminology issue here,  maybe,  but what do you classify as 'supply side'?  Everything I read says nothing to be connected between the output of the vfd and the motor,  so that only leaves the' input,  or supply side to the vfd.  I'm not understanding how an nvr could be used on a control input.


-russ


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Re: 626 mill motor/inverter mods
« Reply #11 on: January 02, 2017, 04:35:38 AM »
Hi sorry a bit of confusion here, I actually referred to NVR function as opposed to the unit itself.
I n the case of my inverter the start is a short making of the normally open "start" switch. The stop is a short breaking of the normally closed stop circuit.
Not that I have any interlocks on my machine as it is too old to have them as standard, if it did the would be in series with the stop button.
Hope this clarifies things.
By supply side i do mean the 240v input to the inverter.
In industry it is not permitted to derive safety interlocks from electronic data, it must be actual switches.
Try a couple of google searches, as always there is loads of info out there, I can't post links on my tablet.
Anyone else care to offer their two penneth Phil

Offline philf

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Re: 626 mill motor/inverter mods
« Reply #12 on: January 02, 2017, 04:59:28 AM »
Hi Russ,

On my lathe (same would apply to a mill) I have an NVR switch on the mains input to the machine. This prevents anything automatically powering up if there is a mains cut. If the lathe is running I wouldn't normally use this switch to stop it.

I also have start & stop switches connected via a latching relay. A spare set of contacts on that relay goes via a forward/reverse switch to the forward/reverse inputs on the inverter.  The start and stop switches are used to start and stop the lathe. The correct decelleration and braking control is then applied to the motor. (As has already been mentioned - if you have a power cut and the lathe is running you don't have the advantage of controlled decelleration.)

Here's my 'crap-o-cad' circuit diagram: (Note to self - must get round to doing a proper cad drawing!)



The forward/reverse switch doesn't drop out the latching relay. I use this when tapping holes.

Chuck guard and change wheel cover switches are connected in series with the Stop button and unlatch the relay.

Hope this is of use.

Phil.
Phil Fern
Location: Marple, Cheshire

Offline russ57

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Re: 626 mill motor/inverter mods
« Reply #13 on: January 02, 2017, 05:11:11 AM »
Thanks guys,  finishing up my mill install including Dro is high on my list of jobs for the year...

-russ


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Re: 626 mill motor/inverter mods
« Reply #14 on: January 02, 2017, 06:35:06 AM »
Hi Philf
Post is a practical solution which covers most of the bases, and does the required. The NVR contractor provides people ultimate protection but as said is not the every day stop start option.
On my wood lathe the stop start is switches are wired solid on/off and no NVR protection whatsoever, when I did my Raglan Metal lathe I did a bit of head scratching and reading of the manual and did the job correctly.
My inverter is a Mitsubishi Frequal and I knew the facility existed but couldn’t find it how to do it, now I have worked it out I really ought to re-visit the wood lathe, using this set up the NVR function is provided by the inverter, no extra power supplies are required the inverter holds onto the last input signal until the power is interrupted, the safety contacts just go in the stop circuit.

Phil

Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #15 on: January 02, 2017, 08:26:00 AM »
Let me just clarify one thing here about my installation.......

I'm running a 1.1kw 3 phase motor via an Invertek 1.5kw inverter.

There is nothing between the output of the inverter and the motor, this is directly wired with 2.5mm2 tri-rated wire....run in conduit.

On the input side, I used the existing wiring that fed the run winding of the original motor. This supply goes via the nvr switch, as did the start wiring( subsequently removed..)

The nvr is interlocked with the chuck guard( although I'm not actually using it, the wiring has been removed) and the pulley cover atop of the machine.

Normal Stop-Start of the mill is taken care of via the Fwd-O-Rev switch that sits along side the speed control pot. These inputs are wired to the control terminals on the inverter.

In the event of a supply interruption, the machine power is cut, in the event of an emergency the power is also cut, this is the job of the nvr switch....it is hard wired and is not subject to the software of the programmable inverter, this is in line with standard industry practise...

So, there you have it...hopefully clear and simple....
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Offline philf

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Re: 626 mill motor/inverter mods
« Reply #16 on: January 02, 2017, 08:32:20 AM »
Hi Phil,

I agree that probably all inverters have a built in NVR function particularly when using the inverter's inbuilt start button. I use this facility on my bandsaw with a Mitsubishi Freqrol inverter.

From memory I couldn't do this on my lathe because I wanted to use the fwd/reverse inputs.

Earlier you mentioned "In industry it is not permitted to derive safety interlocks from electronic data, it must be actual switches."

At the hydro scheme I'm involved with there is an on'off switch on the control panel for each of the two Archimedes screws. We recently had a problem where the PLC got stuck in a loop (bad programming I think) and one of the screws started even though it was turned off on the front panel switch! On investigation it turns out that the switch just connects to a PLC input! I'd be interested to be able to quote to the manufacturers the relevant regulation(s). I was going to change the switch over to a lockable switch but that's of little use if the PLC ignores it under certain circumstances.

Cheers.

Phil.

Phil Fern
Location: Marple, Cheshire

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Re: 626 mill motor/inverter mods
« Reply #17 on: January 02, 2017, 08:57:24 AM »
Hi  John
I was not dissing your install at all I was just trying to suggest that inverters are best not having the supply disconnected as a method of control .
We are both happy with the way we have chosen to wire and control our installations so all good.
So I wish you all the best with the remainder of the tweaking of your machine.
No doubt your are looking forward to its completion and the next phase, making things with it.

Phil

Offline John Rudd

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Re: 626 mill motor/inverter mods
« Reply #18 on: January 02, 2017, 10:05:36 AM »
Hi  John
I was not dissing your install at all I was just trying to suggest that inverters are best not having the supply disconnected as a method of control .

Phil

I'm sure you were not.....and I dont advocate the method of stopping an inverter by hitting the nvr switch....although when I'm finished for the day, I switch the mill off at the socket....not while its running...   :zap:

As an aside, the inverter will self protect ( depending in the make and the software), if it detects an undervoltage it will lockout....unless someone sets the software to restart afterwards.....not necessarily a good thing...

As you say, if we are all happy with the way our machines are wired and operate who cares?  :)

Well back to tweaking... :dremel:

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