vfd inverter for Myford

I've a Super7 with a brook crompton parkinson 50 Hz, class E, PM0.5, 370W motor that was used on a 3 phase supply but I can wire it as mesh/delta for 240v. Does anyone know a suitable inverter/vfd to buy to run the lathe on a domestic single phase supply.?

I have little knowledge of inverters/vfd so would like an easy to set up type.

If this is possible what belt/pulley configuration would you run the lathe with when using a inverter/vfd?

Look no further, the Inverter Drive Supermarket also provide a printable quick start guide which is worth its weight in gold, its so easy to understand.

**LINK**

If you are unsure of VFDs then don't buy a cheap Ebay Chinese VFD. They do work but need some experience to decipher the very poor documentation

Take Old Mart's advice and get a VFD from Inverter Drive Supermarket. Phone them up and ask for a recommendation.

I buy secondhand Siemens 420/440 or Alytivar VFDs , These are good quality units with excellent documentation and cost only a few pounds more than the Chinese VFDs I have installed 5 units so far with no problems.

Andrew.

Agree with above. I have my Super 7 on a Omron 1.1kw inverter that i bought 2nd hand from fleebay for 70 quid. With a 1.5 hp motor. Stonking unit with so many programable parameters. I also have a Toshiba on the milling machine. Do some homework as there are plenty around for not a lot of money. I am not saying the Chinese ones are no good as many members have them & are very happy with them. The only problem with inverters are that initially they are a pain in the butt to get your head round when setting them up. I am an ex Electrician & have fitted hundreds in my career.

It still took me ages to get mine set right. Notepad & pen . Write everything down as you alter it & you then can go back if it does not respond as you expect.

Believe me you will never remember all the settings unless you write it down. My Omron has over 160 different settings.

Good luck. You will not regret it.

The other thing is if you go the Chinese route. I believe the manuals are not the best in the world & some info is lost in translation. Ask Tom Hanks.

The Branded ones have a very comprehensive if baffling manual with them. If you do not get a manual with a branded 2nd hand unit, fear not they are all available free of charge from the manufactures of each unit.

As you commented just wire the motor in the Delta formation & all should be good. Look for an inverter with the same output as your motor. If you cannot find one , you can go for a larger one , but not smaller. Within reason. So if you need a 0.37kw but can only find a 0.5kw it will be fine. In the settings you can set the max output required.

Your standard belt configuration will be fine.

The standard motor will be 1420 approx rpm. With the inverter fitted & run at 50 hz then it will be the same 1420 ish.

The beauty being that if you buy a branded inverter you can underdrive by a huge sum & still get the same power. Using the Torque boost command. If you set the max at around 75 or 80 hz then you can speed the motor up to run at 1.5 times as fast.

Click the link & you will see my setup on the Myford. If you get bored jump to around the 7 mins mark & see how the inverter will make you glad you went down that route. Regards & good luck. Any further info either comment on here or Pm me.

Steve.

Branded inverter on a Lathe.

I have 2 very cheap Chinese ones. The "manual" is a single fold out sheet. No set up was required, just plugged in and off I went. If you want the correct rpm to display then you will need to change a setting and that was pretty simple. Granted they leave you with some guess work when you start wiring in remote buttons etc, but to be honest now I have those working I cant see why I struggled first time around. The instructions are clear enough. Id love to be able to justify a branded western vfd but I'd struggle for multiple machines in the home shop. When I convert the pillar drill back to 3 phase i may I may swap the lathe to a Western one to get better braking for threading up to shoulders.

Several of my friends have bought cheap Huanyang Chinese inverters and I am pleased to say no problems at all. We watched a video on youtube and soon had them working. One came from Leicester, others from Germany for around £80/90 and more recently one friend bought one for £45.Why pay more, and perhaps as VW are having cars built in China, maybe some of the German sounding names on VFD are the same, who knows. Incidentally, I have kept a paper copy of the program and should any one like a copy I'll send them one. As hobby workshop enthusiasts, I don't think we require all the bells and whistles some of the more expensive vfd offer. In my case, I have a very old VFD sold by RS many years ago, programmed via dip switches, does forward reverse and speed control every thing I need. John

Thank you all for your replies; am I correct in thinking this would do the job?

https://inverterdrive.com/Catalogue.aspx?search=atv12%200.37kW

(sorry I did not know how to put a link in.)

If this is ok then could I run it directly from this and add pots and switches to control it later?

I am still a bit confused on wiring it, I presume that you wire from the vfd directly to the motor bypassing the Dewhurst reversing switch, also I notice from Steviegtr's helpful video the belt position he used. Is there a set position for the belt to be left in as I understand that you can vary the speed using the vfd, or am I not understanding something?

Edited By Morgan Sweet on 21/11/2020 12:05:18

Wiring is simply LNE to the VFD (stick a plug on the end and then it isn't hardwired to mains so I dont think electrical regs apply). The 3 phases plus E to the motor. Done. If the motor goes the wrong way then swap two of the 3 phases around.

What I would say is those VFDs don't obviously have controls on the front (run/stop/reverse etc). Watch as some need special programmers to change settings. If that is the case then you'll need remote switches from the get go. Try something like this (mine delivered in less than 10 days). Link deleted see CofC

*****I stand corrected, the buttons are behind the flap. Less than ideal but for the money a compromise you could live with until you wire up remote 'industrial' buttons (you'll want some before long). They have a pdf quick start guide that shows the wiring clearly.

Edited By Mark Davison 1 on 21/11/2020 12:11:39

Edited By Mark Davison 1 on 21/11/2020 12:17:02

Edited By JasonB on 23/11/2020 09:34:18

https://inverterdrive.com/group/AC-Inverter-Drives-230V/Schneider-Altivar-12-ATV12H037M2/Here is the link, the VFD is suitable for a 1/2 hp motor and this model is one of those which IDS include a quick start guide. I bought a larger model for the Tom Senior mill together with switches and a potentiometer for remote control as the switches on the VFD are not intended for normal machine use, just for setting up and are too small to be safe to use in an emergency.

Edited By old mart on 21/11/2020 14:42:22

Changed the 240v motor on my S7 for a three phase motor and and VFD purchased the motor, VFD and remote control station from Transwave also found after sales advice very good. Very pleased the the kit and happy with my lathe

H

Can you say a little more about your experience Harry?

In theory putting a single-phase motor on a lathe isn't a good idea because the motors don't like stop-start work, have low-end torque, are unreliable and vibrate. Yet tens of thousands of Myford owners have done good work with them.

My guess is a 3-phase motor makes the lathe feel smoother and it cuts more confidently. Basically a shade easier to drive with handy speed control and able to cut metal a bit faster. Is that right or do you see any difference in finish or other improvements?

My gut feel is Myford owners needn't rush to upgrade their motors, but it's worth doing when an old single-phase finally bites the dust. How do you rate your lathe now, 50% better or just nice to have?

Dave

Edited By SillyOldDuffer on 21/11/2020 17:02:54

In reply to SillyOldDuffer, I have recently swapped the single phase motor on my Myford 254 for a 1hp three phase unit and Mitsubishi VFD supplied by Newton Tesla. Continuously variable speed is really very convenient particularly as I am idle and did not change belt positions sufficiently often. The lathe seems considerably smoother with a better finish. Part of that is that it is very much quieter and I have more confidence to use highish speeds and heavier cuts. I use indexable tools anyway. Fitting was a doddle as you just plug in, although remounting a heavy motor is not that easy.

Having the luxury of variable speed form the motor should not be an excuse to forego belt changing or using a back gear. Think of it as an additional capability for the machine.

Thanks for all the information, I have probably got emergency stop type switches etc, and potentiometers hanging about to make up a control pod. I assume the potentiometer used to control the speed is just a linear one as opposed to logarithmic.

+1 for all Old Mart's suggestions and advice.

Not explicitly said by him, note thate these units are NOT desigined to be accessible. For safety and protectino they need to be mounted in some kind of a enclosure. The specification / instructions will tell you how much space is required around the drive.

You should also use one with EMC filter buit in unless you are confident in ftting an eternal filter. This is a requrement for safety (interference can cause unpredictable machine operation) as well s being a legal requirement.

Robert G8RP.

That photo of the controls for the TS mill shows the the VFD and switches inside a steel lockable electrical box. The plate visible on the top stands off about 3mm covering a ventilation hole. There is another hole at the bottom provided by the box manufacturer. The VFD frequency when running and "rdy" (ready) and "nst" (no start) LED's are visible through a perspex window cut on the door. All wiring except the mains in is shielded and the box has three plug and socket connections in the rear for the power supply, the motor and the remote emergency stop button.

EMC filters. Not true. No legal requirements whatsoever for home use. Not up on industrial regs any more. But we only fitted them in industry where sensitive electronics were in the same area. Not in every panel. Blue chip companies. They all had there own engineering dept that wrote the specs for control panels. Many with a simple panel for a motor / conveyer etc never had any filters fitted..

I have 2 setups in the workshop & one has a Sony Dab radio directly above it. Never a problem. Wish i could say the same for the el cheepo led light, Sends the radio nuts.

It is nice to have an enclosure like old marts. I have the same setup as him on my Tom Senior. But not on the myford. No legal req for that either, unless there are bare wires accessible & no terminal covers.

Steve.

Agree with Steve. The Schneider ATV12 that I fitted to my mill tripped the house RCD every time from new. The instructions refer to this possibility. It's solved by disconnecting the filter capacitors, a linkage is provided in the VFD to do this. Problem solved, with no adverse effects, but I should say that the wiring run to the motor is short and shielded.

The Teco VFD on my lathe also has this feature, which I haven't needed, so 2 reputable VFDs offering the same cure.

There seems to be some confusion about the purpose of an input EMC filter. It is not there to reduce radiated emissions, but to reduce conducted emissions. So the fact that a radio works nearby is irrelevant. The filter should also protect the VFD from spikes and noise on the mains.

The filter should prevent high frequency noise from the VFD reaching the mains. It should also help with harmonic currents. Simple diode/capacitor rectifiers draw current in short pulses, which has many harmonics. From the generators point of view this is bad. So there are regulations limiting the current harmonics caused by equipment. Larger and/or more expensive VFDs will have a power factor corrector (PFC) at the front end which causes current to be drawn in proportion to the voltage, ie, the current draw will be sinusoidal. In the absence of a PFC the input filter will reduce the current harmonics by passive means.

I fitted a VFD to my CNC mill to drive the separate high speed spindle. Since the VFD didn't have an inbuilt PFC I fitted an external filter. The VFD and spindle were bought as a package from ARC. I've never had a problem with RCDs tripping.

Connection of the shield for the motor connections is a controversial subject. Should the shield be grounded at both ends or just at the VFD? On the high speed spindle I grounded at the VFD end only. While running in the spindle bearings a check with a spectrum analyser didn't show any significant radiated emissions, at least above 1MHz:

Andrew