3-Phase Motor Conversions: Are They All Hype?

Rewired to delta and, pause for dramatic effect, what a difference! On 50% setting, double the DoC used before & it does not bat an eyelid. Bootiful. No speed drop that I can hear.

That you all for your help & comments.

However.

I am a bit miffed that the reseller charges a premium price for the S7 upgrade, but appears not to set anything up. Quite what their added value is to justify the higher price than buying the same bits from, say, eBay is not clear. I will avoid them in future.

As an aside (and not wanting to hijack the “blue chips” thread); one of the test pieces that I used was, I think, an old car king pin. Anyhow, it is rusty, so I think that it is steel. It has a hard band where it used to sit inside a bearing. Hard to turn with the swarf comming off like wire wool. Mostly blue, with an occasional flash of orange. When one bit caught fire, I though it was time to change to a rather more mild bit of steel...

A few years ago one of my friends bought an inverter and was in my opinion was messed about for nearly two weeks before the programming was sorted. When I got involved ( and by the way I'm no expert here) I was told phone after 7 O'clock, then to be told we don't want evening calls, day time only. When my friend call during the day he was told we are too busy to answer queries during the day as we are busy packing parcel and have no time for gossiping. Eventually I got the lathe working, a minor error, but not the back up as the advert said., just sales. Since then I've recommended Chinese made inverters to my friends and all are very happy, especially at the price. John

+1 on the customer service experience from Inverter Drive Supermarket. When I converted my Chipmaster. They were incredibly helpful .I was a complete novice and they answered all my questions and helped me ensure that I was purchasing the correct solution. All for a one off hobby sale. I was a bit embarrassed how much presales time I took up.

Maybe you need to get back to them, so that the person who helped you, finds out that they either messed up, or need more training. Possibly take it further up the chain. The local place here in Hamilton, they will set the drive to suite the motor and the application it is being used for. Really great service too. Companies are only as good as their staff.

Neil

What's your reasoning for not exceeding 70hz on the drive Neil? Most lathes have 4-pole motors which will happily run at the speed of a 2-pole.

Many years ago, when the 1/2 HP motor on my Myford S7 began making noises, I bought a controller from EBay and using a secon hand 3/4 HP 3 phase motor began using a bench setup to test. After some time pouring over the manual and getting nowhere, my son came along to see what was happening. Without looking at the manual he just began tapping the keys on the controller and the motor started. He said that all controllers use the same logic. Did not understand then or now but I have since installed these controllers on the Myford,(with a new 1HP motor) Sealy mill/drill and a shaper. The next project , which has already been bench tested is to fit one with a 2HP motor to my Warco BG600 lathe, although this is a bit more complicated since I would like to retain some of the features of the Warco, such as the leaver start/stop and the safety switches. This is one to ponder over the winter.

I don’t know, definitively, what you mean by “50% setting”. If it is at 25Hz, do not heavily load the motor for more than a short time, or you may/will overheat it. The cooling fan is not effective for high loadings at slow speeds - it was chosen to be adequately effective at its normal running speed.

The same for doubling the motor speed - the fan for a 2800rpm duty would be very much smaller than one for half that. It will soak up far more power at those speeds and may not physically be built, or secured, well enough on cheap motors - so beware! I try to not exceed about 80Hz as there may be other parts of the installation which will not cope with excessive speeds. Plain bearings are one example and chucks may be another.

Edited By not done it yet on 31/07/2018 09:45:01

When I fitted my pre-owned inverter ( originally supplied by RS, no push buttons just DIP switches for programming)several years ago I was aware of the possible cooling problems at slow speed, such as when screw cutting. I monitored the motor temperature and it didn't seem to get any warmer. Having taken lots of small motors to pieces I have never noticed any difference on the size of the cooling fan 2 or 4 pole, I think the manufactures make one size of rotor for both, same with the centrifugal switch a cheap way out, the cost of small motors couldn't justify changes. John

I was told that the motors, 2 pole or 4 pole can safely go to 40% over their rated max rpm.

Neil

You will probably find that a lot of these companies state the continuous output rating. For example on inverterdrive.com they state a continuous and a part time max speed. For the TEC motors the part time rating is usually 200%, or 100Hz for the 50Hz motors with the continuous rating being the much touted 70Hz.

2 and 4 pole motors are most likely to differ only in the stator windings, using the same rotors and bearings. 40% overspeed on a 2 pole motor is about 4000 rpm, so you should be able to take a 4 pole motor up to the same speed and get the same loading on the rotor.

What a difference a day makes. I have been using my lathe much of today and it is a machine transformed. No more worrying about stalling the motor whilst turning.

Thanks again everyone.

Oh, I have left the maximum frequency at 50 Hz. I might consider 60 Hz later; the headstock gives speeds for both frequencies, so I should not be overspeeding anything. Still need to check the chucks, first, though.

Think i know the seller Dave up NW, went through same process after specifically asking such matters. To be greeted with an email stating they dont, consult manufacturers of motor and Inverter but sent a circuit diagram for the pendant controller.
Very dear considering have to work it all out and £19 delivery charge that took 3 days for a pendant is unreal. Same Mitsubishi bought else where around £60 cheaper and arrived 2 days quicker, same with a better motor Brook Crompton motor bought from a dealer in Scotland, next day and at least £42 cheaper.

Still to faff around wiring it in since last October i am just using the motor bought, dare say i wont use the Mitsubishi and pendant it serves no added benefit but hassle and space needed to do so.

I really think that you should name the suppliers. Seems they are in the business of extracting the maximum cash for the minimum of work.

Andrew.

Teco makes motors and state that 2 pole motors from frame size 100 and down can run 5200 rpm or ca 85 Hz all day long and four poles 3600 rpm or ca 120 Hz