Another vfd question

The motor fitted to this Harrison lathe is shown above. I have done a fair bit of reading up on vfd's in the past few days but still have a couple of questions as some of the information I've found is conflicting.

1. Can this motor be run on a vfd if I locate the star point and bring out the connections to a suitable set of terminals?

2. At 2.2 kW it is fairly chunky, so what rating of vfd should I be looking for?

3. What make of vfd should I look for, or what make should I avoid?

Can't read that very easily but it appears to say something like 380 - 420V?? In which case it looks to me as if it would work in delta with a std 240V 3-phase inverter - if you can locate the star point. It's not always accessible, so have a look before you buy an inverter / VFD!

2.2kW is about 3hp. Ideally you would get an inverter with at least 2.2kW so you can make full use of it. If you get a bigger one, you simply have a larger inverter than strictly required but it would be running with less stress. You need to enter the name plate info into the inverter to configure it. This will limit the max current and prevent you from over driving it. I have a 5.5kW inverter driving a 1.5kW motor and it's fine.

I tend to prefer Japanese or German brands. I'm sure there are Chinese brands that will work fine but I have no experience myself.

Murray

1.

Yes but you may not have to bring out the star point, show us a picture inside the terminal box.

2.

2.2Kw, VFD's do have an boost protection to supply something like 100% for a few seconds for starting under load.

3. Any of the popular names but steer clear of the Chinese Hymung <sp> reports seem to be split 50 / 50 between good and bad.

I just returned a Hyuang(spelling?) for being defective, take Your chances. Refund was prompt, in their defense.

Hi Steve,
I'm surprised that a 2800 RPM motor is fitted to a lathe. I would have expected a 1400 RPM motor. I suggest that you post the model number of your lathe to see if anyone can confirm the speed of the motor normally fitted to that lathe.

Les.

**LINK**

this is one that i have

It wasn't easy to get this photo, even with a mirror!

Clearly only three connection posts, so I guess that means stripping the motor. Before I get to that stage I really need to know if it is worth carrying on, i.e. are there some star-connected motors that can't be converted to delta for reasons other than the practical one of not being physically able to locate the star point and bring out the connections?

The lathe is a Harrison 165 - more or less as shown towards the bottom of this page **LINK**

I'm assuming the motor is correct for the lathe but I haven't had a chance to connect it yet so who knows. I have no handbook (if anyone has a pdf I would be eternally grateful!).

just use a 440v inverter like the one on my link

.

Far, far cheaper to buy a 240v inverter and a brand new motor, especially as Les says the motor could be the wrong pole motor.

Transwave sell an IDrive inverter which is basically a IMO for £250 inclusive.

An inverter / motor package is £450 inclusive but these prices can be bettered.

I would expect to pay around £180 for an inverter and £120 for a motor

Hi Steve,
Here is a suggestion to see if the motor is the correct speed for the lathe. Set the speed control levers to the 640 RPM position. See how many turns of the motor pulley are required to give 1 revolution of the chuck. If it requires about four and a third turns then the 2800 RPM motor is correct. If it only requires just over two turns then it should be a 1400 RPM

Les.

Now that is a brilliant suggestion Les

Hi Steve,
I've just realised that I was looking at the picture of the Harrison 155. I can't read the speed selections on the picture of the 165 so I do not know if it has the same speed options. If it does not then you will have to work out the ratio for one of the available speed settings.

Les.

Yes, good suggestion Les. I tried it on 4 different speed settings and got results ranging from 2900 to 3040, so I would say that the motor speed rating is correct for the lathe. The errors would probably be in my estimation of part-turns.

Re Paul 1950's post - looking at the Drives Direct Inverter - is that suitable for both star and delta motors without having to modify the motors internal wiring?

Hi Steve,
I agree that it is the correct motor. The VFD that Paul suggested should be suitable. It does not need to know if the motor is connected in star or delta - only what voltage it requires. (Some larger motors are started in star configuration and switch to delta after a short delay to reduce the starting current.)

Les.

Steve has the lathe got a clutch or is it spindle start?

Pauls may be ok if clutch whereby motors permanently running. Just got to get it up and running from zero with a soft start.
Mines spindle start and startup load way exceeds 2.2kw more like starting a 9hp motor. I have to run the 7.5kw inverter and struggles with a cut on. **LINK**
The 5HP wasn't man enough when up and running, so easy to get spindle to slow and lasted 1hr 23mins, same with Transwave converter slightly higher output.

Should have gone the Mitsubishi 220V output inverter, new motor and remote pod package far cheaper. In saying that years on I have yet to see evidence of 220V output inverters and motors having same torque as 440V.

I'd guess some one has fitted a 2,800 rpm motor to speed the lathe up and also feel that your best option is to throw it away and fit a 1400rpm motor. There are 2 things to look at carefully if you do this. The obvious one is the spindle diameter of the motor but it's also a good idea to check the frame size and fixings as well. You'll probably find that a new motor and inverter is a cheaper option that buy in 240 - 440 3 phase inverter. There is also the passive Transwave converters. I used one of those for a long time. They are fine if the instructions are followed. I thought that I could do a little better and apparently did but eventually I found that under certain loads it didn't work correctly. They are not cheap.

The first option I would look at if the lathe has a clutch, likely at this size, is fitting a good quality standard 240v motor of suitable power rating. Within reason I wouldn't be too concerned if it had a lower or higher power rating. This way you get it up and running at minimum cost and can then see what you have got. Looks like it's a lathe were it's easy to change speed too.

There are catches when inverters are used to vary the motor speed. There will be screams of I do etc and no problems but it's a fact that if speed is significantly reduced and available power used the motor is very likely to run the risk of burning out. Some inverters have thermal modelling built in, eg Mitsubishi but for their own motors. Up market motors with temperature sensing may be available also certain types of inverter motor that have forced ventilation via another motor are available at a cost. The TEC catalogues and data sheets are a good place to look for info on what people usually do also frame and spindle sizes. They make both motors and inverters. Speeding the motor up is also iffy. Not really any info about. I asked Brook and eventually had the answer that he doubted if they made a 4 pole motor that would burst at 2,800 rpm. Up to me to find out. Just about all motors can be run at 60Hz though due to the USA market.

The other thing to realise about inverters is that they don't increase torque when the speed is reduced - gears and pulleys etc do. The inverter will limit motor currents to what is stated on the plate so when speed drops less power is available. They are also noisy. Mitsubishi have a nice feature that helps a bit with that - random switching in the inverter. Helps prevent harmonics being set up in the motor by the switching frequency. I think it's a feature worth looking for if you go that way.

If the lathe doesn't have a clutch I don't think that a 240v motor would be a good idea. A google suggests that it has. There is a Harrison yahoo group. Might be best to ask on there. If you join it wouldn't surprise if there was a lot of info in the files section. There will be people about who know the lathe well too and can help with any problems you might have.

John

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Have a look at Inverter Drive Supermarket. 2.2 kW 230V motor less than £100, inverters from about £110. I used them for both my lathe and mill with no problems.

Russell.

Jon - re the clutch, to be honest I don't know yet! I've only had a brief look so far as I'm trying to finish off an urgent job.

John W1 - I'm pretty sure that with the suggestion from Les above I've established that the 2800 rpm motor is the correct one for the lathe, based on the ratio between motor pulley and spindle.

Having read up on the Drives Direct web site I'm leaning towards their offerings for a solution, one reason being the tech support they offer - it is likely from what they say that they have provided a solution for similar motors before.

I have been a member of the Yahoo Harrison group for a while (in anticipation of getting one). I don't think they have a maual in their archives but I have posted a question or two to try and do a bit more research. With other work I have to do it will probably be a few months before I get it ready to run properly - if I rush it I'm likely to make some expensive decisions!

Thanks for all the advice so far - and more is very welcome.

The inverters are pretty simple to set up, manuals can be bewildering but often there is a section on the important settings and these can be done quickly. It's basically info from the plate on the motor. There is very little info about on the problems with inverters I mentioned. TEC is about the only people who mention it complete with charts. I think that is the brand Drives Direct sell or did start off selling.

I did my lathe on the cheap. Super price reduced brand new Brooke motor off ebay and a used inverter that had little previous use. Like many as I was fitting an inverter I up'd the power of the motor but in turning terms I only drive it at 40 to 75Hz. It's a circa 900rpm motor rather than 1400. I talked to the people who make the stuff as I didn't get reliable answers from the retailers. It's true few people burn out motors at low speed but it does happen. Depends on what is being done and for how long. I did have smoke coming out of the previous motor a couple of times that was the main reason I changed. A Boxford. Problems due to not using the back gear when I should have. I always do now even though there is more power available.

I'm surprised that they fitted a 2,800 motor. I'd guess it was an easy mod for them to make to obtain a faster lathe.

John

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I'd stick with the 2800rpm motor and of course you should be able to crank the speed up a bit higher with a VFD with slightly reduced power. If you are going to use indexable tooling and make anything like proper use of that power, you need surface speed and power feed. The (roller) bearings will be fine. Unless you like standing next to a machine forever, watching the handles turn very slowly, the last thing you want to do is actually fit a slower motor.

Murray