ML7 VFD parts

Has anyone installed a VFD on their ML7?

I understand a three phase motor is required, do they have a recommended parts list?

Cheap/used is OK.

You will need a motor of similar speed and horsepower rating to the existing one....example, 1400rpm, 3/4 hp and an inverter to match with a minimum rating of 1 hp. Physical size will be of the order too, something like a frame 71 size with a 14mm shaft. Ensure the motor is a dual voltage one and is inverter rated...

You might need to do a bit of machining....

There are companies out here that can provide you with a package....( for a few quid....)

Power output is reduced at the upper an lower limits of the motor's speed range, it's often worth going one step up with the power rating to increase the functional speed range available in any ratio.

Compact Frame motors are available meaning you should be able to source a 1hp motor in a frame size normally associated with 3/4hp motors, shop round industrial motor suppliers and rewinders for pricing, the hobby market suppliers charge a premium.

Excellent modification - even better if, like me, you have the Trileva version! Fairly easy to modify the mounting plate to accommodate a non-standard motor size.

rgds

Bill

I have on my ML7. Worth taking a look at Newton Tesla (at least as a place to start), some guys have had positive experiences buying from them.

**LINK**

I've have bought one from them myself but my personal experience was a bit frustrating i.e. didn't send the items when they said they would, charged more than originally agreed and had missing parts in my package! But I don't think that's the norm from speaking to others.

They can build to your 'specs' also e.g. if you don't want the cumbersome control box mount you have an option to use a movable remote with the box mounted elsewhere (I choose this option, much better having the inverter box on the wall IMO). Still required a bit of DIY work to get up and running... But eventually got there and was worth it despite the hiccups...

You can also source the parts and put something together yourself e.g. in this case Beatson "1/2hp BFM B56 resilient mount" motor, Mitsubishi inverter (can't remember the model), plus box, cabling etc.

**LINK**

You might save some money doing it that way.

Edited By mrbuilder on 07/06/2017 04:24:15

DON'T go for any of those expensive packages. Its so very easy to DIY. You don't need a new motor, but you do need one which will fit in behind the head stock, a sheet steel adaptor plate can be made if the mounting holes are not quite the same. There are plenty of good second hand motor around for £20 or less and there is some where on this site a comprehensive article on how to alter the motor from star to delta. Generally there is no need to go inside the motor to reconnect into delta, its a matter of altering the brass links in the terminal box. For an inverter look on the inter net, I bought one for my friend for £95. it is a Huanyang 2.2 kw and its pretty straight forward to program them. It is easy to make up a remote control box for less than £10 if that is necessary.Should you follow my idea send me a PM and I'll send you a copy of the program, and other details. I'm not on commission or any thing else for Huanyang, just a satisfied customer. John

Hello John

I have 95 £ and the motor is already in place.

If lathe is running on the Huanyang happily and power disappears and come again,what happens?

In reply to Nigel above, you have to press the run button once again, or you can do as I have done, connect a 20 amp 240 volt relay BEFORE the inverter input, the relay also give extra NO-Volt release belts and braces. Nothing between the. inverter output and the motor..

Brainsparks,

I sent you a private message regarding a motor.

In my view inverters are best thought of as devices to close the gap between fixed belt or gear speeds giving a seamless speed range. Typically a good device will give you ± 1/3 rd of nominal nameplate speed with little enough variation in effective power output as to be unnoticed in normal use. The better VFD's are engineered to increase drive at lower speeds giving more torque to partially offset the inevitable power loss as speed falls.

Outside the ± 1/3 rd range things start getting compromised. Things still work just fine but you need to be aware of whats going on. In particular at lower speeds power loss becomes noticeable and internal cooling fan efficiency falls drastically so there is a risk over of overheating. Generally inverters are pretty good at only delivering the power the motor needs so the overheating issue isn't as bad as some might fear providing loads are light. Power loss is the main issue as, usually, low speeds are required to deal with large components so the power increase when belt or gears are used to reduce spindle RPM relative to motor speed is very desirable. The speed increasing capability of an inverter can really score here as permitting you to use a lower speed fixed drive setting and run the motor faster getting even more power onto the work. Conversely when you are cutting a short thread, winding a coil or spring or its great to be able to crawl round.

its important to consider back gear speed capabilities. Open gears, as used on most small machines, aren't happy if run too fast. Many makers advise that the highest input belt speed should not be used with back gear.

It has been convincingly argued that best practice is to reduce the countershaft speed for VFD use by fitting a smaller pulley on the motor. Generally high speeds are only needed for small work so power loss when running fast is hardly a worry. Setting up in that manner lets you run in open drive down to rather lower speeds. Which, if nothing else, is quieter than back gear. Biggest problem is getting satisfactory drive from a small Vee pulley on the motor. Which are usually undersized as standard anyway. Multigroove belt systems are much more satisfactory. Suitable belts are readily available these days and pulleys easily made or reasonably priced if you don't fancy the work.

An oft overlooked advantage of VFDs is the very repeatable run down to rest time after hitting the stop button. Correctly programmed with a suitable microswitch arrangement connected to the remote control inputs this can be exploited to make an excellent electrical bed-stop for cutting to threading to a shoulder purposes. At moderate speeds maybe half a spindle turn from switch to stop.

Clive.