Inverter wiring question

[Deadeye]

Hi again
About to take the plunge and wire up my lathe with an inverter. I'm intending to take pictures and document so others can avoid my inevitable mistakes!

There will doubtless be other cries de coeur along the way, but hopefully the first two questions are easy ones.

1. The inverter has a control panel (start, stop, forward reverse, speed dial, and digital speed readout as well as the programming buttons). This is a separate piece that clips into the body of the drive on about 20cm of 5-core ribbon cable. Presuambly there's no reason not to extend the ribbon cable and use that panel as the lathe control? It'd save an awful lot of wiring! I can't find the same connector, but if I snip the ribbon I can just put an extension in with a chocolate box at each end?

2. I'd like to maintain the microswithces in the top and base of the lathe. Can I do this an easy way - i.e. put the existing on/off and microswitches upstream of the inverter so that they operate on the 240V inbound and turn on/off the inverter? I want to leave the lathe as intact as possible. The lathe is currently 3 phase (I'm ok with reconfiguring the motor to delta I hope) are the microswitches liekly to be complicated by being on a 3 phase machine? Will they work on single phase inbound and 240V rather than 415?

Thanks once more!

 

[Inspector]

Re extending the cable. My VFD came with a 2 metre one with plugs at either end. I can't remember what it said about adding longer ones and I don't feel like digging through 200 pages to find out. :wink: The manual for yours should have that information. I wouldn't cut it, I would replace the wires if you can open the parts up.

Pete

 

[jimmy_s]

I'll try and help -

regarding point 1 - I can't see why you couldn't extend the wiring but best to check the manual. I fitted a drives direct inverter to my bigger metal lathe about 10 years ago so I can't recall exactly what I did but the inverter I got had auxilliary inputs. I wired the speed controller via a potentiometer from the lathe headstock back to the inverter and also wired the forward/stop/ reverse lever back to the auxilliary contacts - the inverter is about 2m away from the lathe and I have never had any issues.

Point 2 - I presume the micro switches are on covers etc for safety? If its a three phase machine I would think there's a good chance its wired to start/ stop through a contactor. I would think the micro switches will be wired in series with the contactor coil that is energised to pull in the main contacts and start the motor so the microswitches will not see full load current of the motor. I would check them with a multimeter and would expect them to be mormally closed and would open when a cover is opened? I wouldn't want to wire them upstream of the inverter as they are probably not rated for that sort of current. I would disonnect the lathe power wiring and wire them in series with your auxillary on/off contacts or check the inverter wiring diagram to see if you can identify a set of contacts which will de-energise with a break in the circuit - and wire the microswitches in series to these contacts.

hope that helps!

 

[deema]

A good project, I’d suggest the following
1. Although feasible I wouldn’t. The control panel switches will in all likelihood not be robust enough for everyday usage. The two options I would look at are
i. Using the existing controller, buttons on the lathe. If they are contact buttons then they will be fine, latching buttons may not work with your VFD as you would like.
ii. Buying and adding proper industrial push buttons, they arnt very expensive.
I would also add a proper mains switch (live and neutral) that’s illuminated / power in lamp) to the control panel somewhere) rather than relying on just pulling out the plug.

2. The VFD if it’s designed properly will have an emergency brake / shut down option. This will require you wiring one of the outputs of the VFD to the micro switches. The output will probably be around 10v, which means that the existing switches are more than sufficient for your needs. When activated either the VFD won’t start, or it will brake the motor within its capabilities. The larger VFDs have the option to add a braking resistor which is also used to stop the motor when the off button is pressed.

 

[Hornbeam]

The mircro switches can be wired into the 10-12v control side of the Inverter.
I was told regarding emergency stopping not to cut the 240V supply but to do it through the control.
The programme in your vfd should also be able to alter the ramp up/down speed on normal start stop. The faster you ramp up/down, the harder the inverter has to work ( this is different from emergency stop)
Ian

 

[Deadeye]

Thanks everyone - really helpful, as ever.

I'll definitely put a proper on/off box on the 240V supply; the plug is right by the lathe so it's trivial.
It'd be nice to "do it properly" and use the existing controls, so...
The on and off buttons are one-press (i.e. they don't latch. A NO On and a NC Off with a common. The microswitches are in series to the NC. The whole lot goes down to an device (name unknown!) with an electromagnet that bridges the terminal pairs when activated. The On switch powers the coil and then it gets bypassed by the NC circuit. So as far as I can work out, the microswitches *are* carrying the full current?

What I'd originally planned was essentially substituting the VFD for the motor. If I call the terminals 1 2 3 & 4 starting with the one with tthe red button (so motor is on 2,3,4) and A B C D on the other side (with red on B C D), then I was planning: 2 & 4 to the VFD. B and D live and neutral 240V input.
Control white to 1 (on button). Control yellow to A (common) and control blue to B.

If I try to do it more elegantly then the VFd has 12V; X1-6 and Common; VL1, 5V, SP1, and another common.
I can put the speed dial on 5V/VL1/Common.

X4 is described as Forward rotation control switch and "short port X4 and Com, input signal effective". Does that mean that the connection must be held closed? So my current On switch wouldn't work? Or will a single signal

There's X5 to hitch up a reverse switch (so that's ok).

The other multi funtion terminals (X1-3 and 6) can be programmed to a range of functions - including "emergency stop" and "relay control". So I should set X1 to "emergency stop" and put my all my NC switches in series to that? But shouldn't they then be NO?

There's also TA, TB and TC marked as "relay output (optional)", but those are solder points, not chocolate box.

Advise hugely appreciated as always!

 

[jimmy_s]

Hi Deadeye
The electromagnet part is the contactor and the bit with 10A on it connected to the outgoing terminals from the contactor is the overload. The contactor coil seems to be a 415v coil that will work between 2 phases - phase to phase voltage is 415v. Your control cct will be wired from the on/off switches to the auxilliary contacts on the contactor so when you press the on button the coil will pull in the contact block to power the motor. The control wiring would normally run through your microswitches in series and if either m/s was open cct the power supply to the coil would be interupted and the coil would be de-energised and the machine would either not start or it would stop if running.

None of its going to be useable with your inverter I would think. If you wanted to re-use the start/ stop buttons I would think you would need to use a relay with a 240v coil and contacts which could be picked up by your inverter auxillary inputs I would think. Who's inverter is it and do you have a terminal/ wiring diagram for it? - that would be the best bet to help sort this out.

 

[deema]

That is I believe a union Graduate lathe. A very nice lathe, I also have one. I have converted a number to run of a VFD. I use a WEG VFD, it will mount on the back of the box in which you found the contactor. There are 4 bolts holding that box in, just remove them and bolt the VFD onto it. It will fit. It’s nicely protected from just about everything, and the cast housing provides great EMC shielding.

Dump the contactor, and I would also dump the switch panel off the front of the machine. If you buy the WEG switches and the WEG potentiometer, all available from Inverter Drives you can build them all into a piece of plate you replace the panel with. Forward, reverse, main isolator, variable speed controller and a nice on and off button.

The WEG100 and the expansion module is what you need.
https://inverterdrive.com/group/AC-Inve ... A01P6S220/

The step by step guide that can be downloaded from the site makes wiring up and programming easy.

Here are pictures of two recent ones I’ve done. One is silver and the other is Graduate Grey. Both are original colours used for the machines.

 

[Deadeye]

Thanks again all.
I spent a good few hours yesterday and made some useful progress I think.

I got the motor out (which was tough as the collar was rusted onto the shaft) and have re-wired to delta. Connected it to the VFD, and the VFD to the mains plug (via a switch and both with the cable folk here advised - thank you) and it runs beautifully from the VFD control panel. So far so good!

I then spent an enjoyable afternoon playing with the parameter configuration on the VFD. I removed the switch panel from the lathe and have now managed to configure the "On" momentary button to switch it on and the off to switch off by taking the three control cables into the VFD external inputs.

I'm out for most of today, but the next tasks seem to be to test wire the potentiometer (Bourns - again grateful for the advice here). That needs soldering, which I'm a novice at but youtube seems to cover pretty well.
I'm also going to test-wire the micro-switches in series with the stop.

If that all works, then I might get brave and try to add a reverse and jog. (although I'm not sure when I'd use either, but it seems sensible to do whilst it's all in bits).

I rather like the original buttons, so am thinking to put a small second box on next to the original, with the potentiometer (and perhaps reverse and jog).

A couple more really numpty questions though:
- I was planning to mount the VFD enclosure box either between the rear legs of the lathe or on the back. I've a preference for the former as it's unused space now and I can make a cut-out to help the heatsink a bit without spoiling the dust protection. Are there reasons not to do this?
- The VFD has a 200mA, 12V output on the control bar. (Well it says 12V on the device but 15V in the manual). If that went through a small fan for example, where does the return wire go back to?

Thanks again!

D

 

[Myfordman]

If the inverter needs a fan then it will already have one. No point in adding one. It will have an over temp sensor to shut down safely.
The 12/15v supply is there for any external switching logic that might be needed not for fans.