Hardinge lathe VFD install

[Pete.]

I've spent all day today removing the old electrics from the cabinet on my HLV and fitting it out with a VFD and modern relays etc.

Here's the original cabinet, with fwd/reverse contactors, overload, pump relay, a myriad of fuses and the rectifiers for the DC traverse motor on the carriage.

And here is where I've got to with fitting it out to run from a VFD:

So I've got power coming into the bottom left corner feeding the main contactor and the NC stop switch via the red wire though a 2a fuse (no2). Top button pulls in the main contactor which feeds the VFD via fuse no1 and the pump contactor via fuse no3. The second button pulls in the pump contactor and both contactors latch themselves on so losing the power or hitting the stop switch drops either or both of them out.

Tomorrow I have to do the control circuitry but right now can anybody see anything obvious that I should (or shouldn't) have done with the power circuitry? (I know the yellow earth wire is wrong but I don't have any heavy enough yellow/green just yet).

 

[daleyd]

Are you planning on having the stop switch as an e stop, so a “normal” stop the drive remains powered.

 

[Spark plug]

Inverters sometimes don’t like to loose there power when running, I have known them die quite horribly.

I would wire the machine so the drive is powered all the time the machine is on, like the machine light, then use start and stop buttons to start / stop the drive. But run the output from the drive through the E stop contractor.

 

[Seadog]

Surely the last thing you want to have is a contactor between the drive and motor for the E stop? That will remove any braking control and the motor will then freewheel to a standstill.

 

[Spark plug]

Surely the last thing you want to have is a contactor between the drive and motor for the E stop? That will remove any braking control and the motor will then freewheel to a standstill.

It would have the same braking charictoristics it would have before the VFD was installed, it’s not a big lathe and will have very little rotating mass so will stop itself easily anyway.

If it where a bigger lathe with lots of rotating mass then yes it would be worth doing things differently

 

[Pete.]

I should have made it clearer, there's no control circuitry right now - starting and stopping is done by the lever on the front of the machine. I've got to wire that all up yet. These buttons only supply power to the various components so I won't be interrupting the power whilst running.

I'll have to think about the pump though as currently the only way of stopping it is by killing power to the whole machine. Perhaps I'll fit a second stop button just for that.

BTW I'll be fitting a braking resistor but the HLV has a brake on the motor pulley as standard. It's held off by a coil so if there's a power loss the brake comes on automatically. The very bottom switch is a bypass for it and I intend to control it via a relay on the VFD output. Should stop pretty handy

 

[Pete.]

Got the cabinet finished as far as the motor controls go. I've re-fitted the original rotary switch and that now does the fwd-reverse inputs for the VFD and energises the solenoid for the electric spindle brake. I've left the switches how they were because I've found that bus voltage stays healthy on the drive for a good 10-15 seconds after hitting the stop button, so I can hit the stop switch to stop the pump and straight away hit the ON switch to keep the drive powered. The switch at the very bottom is a bypass for the brake solenoid so you can hold it off with the spindle not running, and the one above it which was fwd/rev is now the fast/slow switch for the motor. Low speed gives from about 120 to about 1000RPM, fast gives about 350-3000RPM using the vari-speed pulleys.

 

[Hopefuldave]

It would have the same braking charictoristics it would have before the VFD was installed, it’s not a big lathe and will have very little rotating mass so will stop itself easily anyway.

If it where a bigger lathe with lots of rotating mass then yes it would be worth doing things differently

**ALL** VFD manufacturers warn not to put **ANY** kind of disconnect between VFD and motor, and won't honour any warranty if you do - disconnection under power causes large transient voltages due to the inductance of the motor windings, arcing in the contactor/switch, probable breakdown of the IGBTs in the VFD output stage with loss of the Magic Smoke.

Most VFDs can have a digital input programmed as E-Stop and will do their best to brake the motor to a halt (even without brake resistors - which I recommend, not expensive from those Chinese gentlemen, and a lathe that stops on a groat when cutting non-native threads with the half-nuts locked in or turning to a shoulder is very much worth having - although your Hardinge may have the leadscrew reverse and stops?)

Dave H. (the other one)

 

[Seadog]

disconnection under power causes large transient voltages due to the inductance of the motor windings, arcing in the contactor/switch, probable breakdown of the IGBTs in the VFD output stage with loss of the Magic Smoke.

Not necessarily the first time you do it, though. It may survive repeated e stops, but each time the IGBT junctions will be damaged until you reach the point that they give up the ghost.

 

[Hopefuldave]

Not necessarily the first time you do it, though. It may survive repeated e stops, but each time the IGBT junctions will be damaged until you reach the point that they give up the ghost.

Yup, makes life difficult for those of us with Odd Old Machines - my lathe has a 3-speed motor, I've had to add interlocks on the speed change switch/lever to put the VFD into "coasting" mode when changing, then added VDRs, load-side chokes on the VFD output... All to keep the "Holbrook experience" of speed-changes on the fly :/

Dave H. (the other one)

 

[Pete.]

I've fitted a braking resistor to the VFD. Manual says 39ohms was the ideal value I had some spare rheostats that I salvaged out of a lift switchgear cabinet about 6 or 8 years ago. I adjusted the clamps for 200ohms by moving the ends in together then I linked the ends together and tapped the middle contact effectively making two 100ohm resistors that I've now got in parallel combining to make one 50ohm resistor of double the current carrying capacity of the original rheostat (which is unknown to me).

The resistor is definitely working because if I give it a few high-speed stops it gets pretty warm.

I've also discovered that the WEG VFD has DC injection braking (@Barlidge take note because this is the twin of the one on your Bantam) which can be set to come in at any frequency below 15hz. Now I've enabled that the motor stops in an impressively short time especially in slow speed. At 150RPM it'll stop in half a turn.

 

[Ianb]

Can setting the braking time to too quick cause any problems with over loading/wear to the motor, got a Colchester Bantam with a vfd and it was set to a very slow ramp up and down, maybe just default values, so I reduced it to 1.5s if I remember right, was concerned it could strain the motor/gearbox, but if its not a problem I will shorten, dont mind the smooth ramp up, but it always seems such a wait for it to stop!

Very tidy wiring, what is the silver sheathing on the grey twin and earth going through the hole, is it a protective covering?

 

[Pete.]

MY manual says that the braking load can be up to 100% of the motor full amps, though it does say you'll get only 10-35% without a resistor. My drive will display the DC link voltage, heatsink temp, motor amps and other things and you can watch it when under accel/decel. I found that a 1second decel from 1000rpm (spindle) with no chuck didn't raise the DC volts much and the heatsink never raised off the 25degC minimum value.

You can go much better than 1.5 sec I would be comfortable going for half that if you have a good VFD. With a resistor fitted mine is now at half a second.

 

[Ianb]

Thanks for info, I will recheck the manual as I dont have an external resistor fitted, which then iirc limits me to the type/amount of braking

 

[Pete.]

If you go too short on the braking time the drive will fault. Wind it off a bit, and take care if you have a heavy part in the chuck. I'd set it up with a big chuck on it so you know that at all other times it's going to be less stressed.

 

[Barlidge]

I've also discovered that the WEG VFD has DC injection braking (@Barlidge take note because this is the twin of the one on your Bantam) which can be set to come in at any frequency below 15hz. Now I've enabled that the motor stops in an impressively short time especially in slow speed. At 150RPM it'll stop in half a turn.

Thanks Pete, the settings are still as you set it up.

 

[shades.of.blue]

Hello. I was so excited to find this thread. I have the exact same Hardinge HLV-b narrow bed. The machine came with electrical issues. and was not running. Some of the contractors had the coil pack burnt... I am between redoing the entire electrical and using VFD and updated components just like you did here Pete. . I am not very experienced in this type of electrical conversion and would love to copy exactly what you did here on my machine. It also occurred to me that you possibly still have the original contractors that you removed to install the new components. If by any slim chance you still have those electrical parts and would be interested in selling them then that may make my work easier. If you have any tips on how to copy the electrical work you did I would be extremely grateful.
Thanks.

 

[Pete.]

If I had them, you would be welcome to them for the cost of postage, but sadly they went some time ago. I will have a look around in case I have any bits left but I'm pretty sure I don't.

I do have one side of a field coil for the travel motor I know that much.

 

[Sc00ter80]

I've spent all day today removing the old electrics from the cabinet on my HLV and fitting it out with a VFD and modern relays etc.































Here's the original cabinet, with fwd/reverse contactors, overload, pump relay, a myriad of fuses and the rectifiers for the DC traverse motor on the carriage.















































And here is where I've got to with fitting it out to run from a VFD:































































So I've got power coming into the bottom left corner feeding the main contactor and the NC stop switch via the red wire though a 2a fuse (no2). Top button pulls in the main contactor which feeds the VFD via fuse no1 and the pump contactor via fuse no3. The second button pulls in the pump contactor and both contactors latch themselves on so losing the power or hitting the stop switch drops either or both of them out.































Tomorrow I have to do the control circuitry but right now can anybody see anything obvious that I should (or shouldid dn't) have done with the power circuitry? (I know the yellow eartWhich wire is wrong but I don't have any heavough yellow/green just yet).















Hi which motor leads did you use to go to the vfd do you know there numbers














W

 

[Sc00ter80]

I'm trying to do the same Pete, which leads from the motor should I use