How to set up a 3 phase inverter & motor for a beginner

Hi guys & gals. I am looking for a used 240v to 3 ph inverter to do a complete series on how to connect a 3 phase motor to a single phase inverter. To the hams a (VFD) Anything around 0.38kw to 0.5kw will do the job. This is because i have a spare 0.38 kw motor & have been asked by quite a few people to do this video for them. Larger i suppose would do too. This will include how to make a small control panel to use with it if required. I had lots of these when i retired & foolishly sold them at car booties for next to nothing.

As everyone knows this would be quite volotile to post on this forum. But i am going to at some point. For the Rocket scientist's out there please do not comment. I have had a lot of interest from my subscribers to do this because it frightens the living daylights out of some guys when the word 3 phase is mentioned.

This will be from safely using the correct type of cheaply obtainable terminals . To connecting correctly. To using the proper type of SY cable . Earthing will be important. Do i need a remote panel as lots of folk say yes. No you do not. Some question asked were can i switch the inverter from forward to backward without causing damage. The answer is of course you can many time a minute. Me & my company built many control panels that required a piece of equipment to run back & forth at different speeds. I designed in autocad & priced +built many of these such panels. They ran for many years with little or no trouble.

When i eventually do this series, all i ask is that a few members refrain from negative comments which will spoil it for the many that will benefit from my experience. commenting which usually gets the thread deleted. Just the the 3 of you. As I know you 3 are superior to to anyone else on the forum & would spoil what could be a learning curve to those who fear fitting a new motor to there machine.

There are more than you think. Don't be afraid guys it is very easy & after a little bit of programming which SOD, Robert & NDIY will walk you through will run perfectly. Keep an eye out for the vid.

Steve.

Steve, I'm not sure sarcasm is the most effective way of avoiding argument.

There's no issue about discussing 3 phase on the forum. My own article::

www.model-engineer.co.uk/news/article/3-phase-conversion-and-other-alternative-methods-of-powering-a-mini-lathe/18752

But obviously, people should only work with mains voltages if they are competent to do so.

One area that will always be one of contention is proper shielding for RFI - not helped by some manufacturer's guidance being completely contradictory to that of other manufacturers.

Neil

Point taken. Maybe not post it here when done. 

Steve.

Edited By Steviegtr on 10/01/2023 00:41:59

Was going to comment on this but thought better of it. (for the good Steve)

regards

I think CY cable should be used for screening, SY is a mechanical protection braid.

Mike

I've read a lot about a competent person, out of interest try to find out how one actually becomes a competent person be it gas or electricity Give your self plenty of time. John

John, I always had similar thoughts about the Authorised Personnel Only signs that cropped up regularly. I argued that anyone can deem themselves authorised in their own mind. The same goes for competent without some definition of what is meant by competent.

Martin C

Having writen an article for ME sometime ago, and having seen how some will split hairs or require the highest standards of safety or professional knowledge even in the hobby field I felt that It was better for all concerned that I do not submit it for publication, even though it involved voltages below 20v. It had been written on the assumption that the reader was an inteligent being - may be a dangerous assumption !

After the Chinese Diesel Heater episode I would be very wary of bothering Steve ! There are some here who know so much that even when the facts are looking them in the face still insist their right !

Good Luck. Noel.

I guess that the electrician who wired our immersion heater to the lighting circuit, and his apprentice who buried an LED power supply puck inside the loft insulation so that it overheated and burned out, would claim to be "competent persons". Frankly I thought they were a walking menace to the public.

Easier to identify incompetent persons, but even they get away with murder! And then despite obviously questionable results incompetents often attract bands of loyal followers. It's a funny old world.

Dave

Competent person? That would be covered here so it seems to be not so woolly after all. Says the man who was a competent person to fit a 13A plug and had a card to prove it. Yes really!

With RFI you may get trouble if the VFD spec says apply RFI controls and you don't and someone complains. If it's not mentioned then you can shrug I guess. There was an RFI issue at Heathrow due to someone unplugging a live CATV feed in a Brentford flat and screwing up aircraft on approach flying straight down the Brentford main drag, as they do.

John, if you haven't found an electrician yet use the following link, just enter you postcode to have a choice of NICEIC registered persons/firms in your area.

**LINK**

Emgee

Steve do yourself a favour post it on youtube because they'll pick it to pieces

H

Looks like the haters have already started. Not sure I want to be on this forum. Will have to give it some serious thought.

regards

1/ If this is for youtube, ask your subscribers to give you a VFD.
2/ A used VFD is a bad idea. Firstly it may have a fault or fault(s) that could be intermittent or unusual settings that cause trouble. Secondly it may be older model no longer available.
3/ A control panel IS required, remote or on the box the VFD is in. The controls on the front of VFDs are for set-up and test, not routine operation. and you can't get at them without opening the enclosure. You will be putting it in an enclosure won't you?

If you post here or on youtube any registered user can comment. its part of the process....

Robert G8RPI.

Edited By Robert Atkinson 2 on 10/01/2023 17:31:44

Thanks but this was several years back. I'm sure the firm was registered, my point was that they were incompetent.

Yes I did a full day's internal works course for that myself, and came away with the relevant certificate.
The very last part of the course covered that we were now not allowed to insert the plug into a socket, until we had booked an appointment, travelled to a different location and had it PAT approved by our local tester.

Someone on high had deemed it ridiculous that us engineers couldn't fit a plug, but hadn't quite thought it through.

Similarly the testing engineer was told that any mains equipment, not supplied via our official stores catalogue, must have the plug cut off and be skipped, other wise he would be formally disciplined as breaching the company's H&S rules; He then pointed out that would also include his PAT machine.
Ho Hum.

Bill

Edited By peak4 on 10/01/2023 17:33:59

Going off topic, but one issue with the registration route like NEC-EIC is that only ONE employee needs to go through the registration process. They can then, if they wish, delegate the authorty to do the work to others. They do of course remain responsible but it seems some don't realise this or just don't care as long as they make money.

For electrical work, including "Part P" you don't have to registered or have any qualifications. Though in that case you would have to convince the building inspector that you are competent (accepting anything less than the usual qualifications is entrely up to them and why should they?) and then pay their fees to record the work. This is not normally cost effective.

Robert G8RPI.

I am struggling to see the point of the OP. Is it to cadge a VFD, gauge opinion, or a combination of the two?

There is no need to be a registered competent person because that is to do with fixed wiring. (I was one once.)

It really is a matter of following the manufacturers' instructions and tidy workmanship.

Don't let the "haters" get to you - nor wind 'em up by calling them that.

Nevertheless...

If you are installing anything electrical in your workshop for hobby use, only you need and can judge if you are "competent" within the meaning of... but it is wise to consider your abilities very carefully. If any doubt find a reputable electrician, preferably with industrial wiring knowledge; although the task is not technically difficult if you are using a purchased, complete set provided with the circuit-diagram and instructions.

I have fitted 3ph conversion sets to four machines: a Harrison L5 and a Myford ML7 lathes, a Myford VMC mill and a BCA jig-borer; but for each case bought an appropriate motor and electronics set (Newton-Tesla) having told them for which machine; and I followed their instructions very carefully. Though my years of specialist electrical and electronic assembly work did help me..

The ML7's electronics are manufactured as self-contained in a single box I could screw to the cabinet, with a simple shield over it. For the other machines I placed the inverters well away from the moving parts and swarf, with the important point about thinking where to put the controls. (They are in separate units.)

That for the Harrison lathe is above the tailstock, within reach when standing in the normal spot, but needing my arm move away from the chuck to use it. Though I still need use the clutch lever in its horrible designed place above the headstock!

'

One important point. Motor speed!

The motor still needs run fast even if you want the chuck to rotate slowly, so don't be swayed by those who advocate throwing the machine's pulleys and belts or gearbox away! It allows maximum torque and slow cutting speed / feed without over-heating the motor by its fan barely spinning - I am not sure if there are other potentially deleterious effects.

The controller on the N-T sets has its red sector at low, not high speed.

.

I find using the ML7's direct drive on the middle and low spindle pulleys covers most turning, back-gear for screw-cutting or as otherwise applicable , without stressing the well-shielded motor.

The L5's spindle speed is around 60-70rpm in lowest gear with the 3ph motor, on a frame above the headstock, happy at around 900+ rpm, according to the controller scale.

The milling-machine still has its 2-stage belt and pulley arrangement, and that will stay despite being awkward to use, unless I can design some better system. Or more accurately, physically make it...

The BCA is a fast-running machine anyway so the existing belt drive from the replacement 3ph motor is fine.

I am recommissioning a small horizontal mill (Denbigh H4) but will stick to simple 1-phase motor and mechanical transmission for that. It does not need anything sophisticated. In fact only today I collected a mechanical variable-ratio drive to use on it, from a private-seller advertising on this very Forum!