Harrison M300 Lathe VFD and motor options

I have recently acquired a new-to-me Harrison M300 lathe. It comes fitted with a 3-phase 2.2 kW motor (can be wired star or delta) and I plan to fit with a suitable VFD. The M300 will replace a Boxford model C (now available for sale) and a superior Denford Viceroy TDS 1/2 PCS (the model with powered cross feed) in due course. However, I digress.

I'm looking for comments on the following options.

Option 1: 2.2 kW motor and VFD

Looking at the specification for 2.2 kW output VFDs it would appear the input current can reach about 24 A. This seems rather high but I'm guessing it is maximum inrush current and/or transitory overload. It wouldn't surprise me if many users of cheap import 2.2 kW VFDs use a regular 13 A fused plug and bearing in mind my lathe will be used for light duties only (I bought it for features, rather than throughput) I could possibly do the same, maybe tweaking the VFD configuration. If this didn't work out, I could get a 32A socket fitted but this lacks some flexibility for me as I occasionally need to move machines around in my home workshop.

Option 2: 1.5 kW motor and VFD

Another option I have considered is to fit a 1.5 kW motor (I have no shortage of spare motors from 370 W to 2.2 kW) and fit a smaller VFD. My preferred drive (WEG CFW300 IP20 1.5kW 230V 1ph to 3ph) has a maximum input current of 16.1 A and I'm reasonably confident this will run from any 13 A socket given my use-scenario. This will down-rate the capability of the lathe but most likely exceed my personal needs. If it proved inadequate I could refit the 2.2 kW motor and replace the VFD. That would prove expensive.

Option 3: 1.5 kW motor (trial) and 2.2 kW VFD

This leaves me with the final option: to fit the 1.5 kW motor to assess performance using a 2.2 kW VFD. The 2.2 kW VFD is marginally more expensive than the 1.5 kW option. The 2.2 kW VFD would of course be configured to match the 1.5 kW motor and I assume (but do not know) it would run without problem on a standard 13 A plug as per option 2. If the motor output power proved inadequate for my needs (unlikely, but possible) I could refit the 2.2 kW motor and go to option 1.

I personally would go for option 1. You already have the original 2.2KW in place and as you say the cost of the 2.2kW VFD is not that much extra. This will keep the lathe in pretty much original configuration which will help keep its value should you need to sell it. Dont’t forget that it will only draw 2.2Kw on full load. I would reason that most of the time motor inefficiency aside, the amount of power required to take a cut at given rpm will be the same whatever kW motor is used. In addition you may find a 1.5kW unit may struggle to run the lathe at top rpm especially in cold weather whilst taking a decent cut.

I run my 1.5kW lathe off a 16A radial circuit, but I am confident it would be OK on a 13A plug. I run my 2.2kW mill on a 25A radial and a type C breaker as advised in the VFD manual, this I believe reduces the chance of tripping.

Tony, thank you for your reply.

Assuming I keep the existing motor (not yet decided) it will need to be reconfigured delta. Taking a closer look at the motor I see two issues.

Firstly, the motor data plate rating is 40% ED. If I understand correctly, this is a 40% duty cycle assuming full load Please correct me if I am wrong. In other words, the motor could be used at its full rated power for 4 minutes out of every 10 minutes. Without seeing a graph, I am unable to determine the duty cycle at other (more realistic for me) loads. Would it be 80% duty cycle at half power? This could be a problem.

Secondly, the motor connection box is presented with 9 labelled wires. It appears that someone has removed the original connection points and links. U1, V1 and W1 go to the power supply. The remaining 6 wires are paired as follows: U5-U2, V5-V2 and W5-W2. The connection plate identifies 220/440V is possible, as is YY/Y connection. I don't see any reason why this cannot be wired delta when I figure out the connections.

I've found a couple of useful links

• https://my.motovario.com/technical-data-2/m/iec/std/catalog/series-and-hookup-a169/
• https://www.wat.com.tr/baglanti-en/

and it appears the 9-wire motors have the star point "hard wired" in the windings. This may incentivize me to consider using another motor.

I've got 4 of the 2.2kw cheap Chinese VFDs running everything from a 2.2kw motor on my Colchester bantam, a 1.5kw on a harrison mill to a couple of small motors on a meddings drill press and clarkson cutter grinder. The only issue i every have is cranking up the speed on the mill whilst the gearbox oil is cold (ISO220 oil). The VFD will throw a over current error.

I wouldn't contemplate down grading the M300 to 1.5kw. If there is any chance that you are going to trouble the current rating of a 13amp socket with 2.2kw motor then a 1.5kw is going to frustrate you with a lack of power.

The 9 terminals make it sound like a 2 speed motor. Im pretty sure you can't make use of the 2 speed switch whilst using the vfd (temporary disconnection of the load under power whilst switching i suppose).

If I didnt need 4 VFDs I'd have bought a branded one and forked out what will now no doubt be £250 for the 2.2kw on the lathe, but to be honest I've never had an issue with the Chinese one (only ever on the mill and thats easy to work round by warming up the oil first).

The main thing that would push me to a western branded VFD now would be politics, but that would mean the western branded one couldn't be made in China!

Edited By Mark Davison 1 on 25/10/2022 05:36:22

Edited By Mark Davison 1 on 25/10/2022 05:39:21

There are a couple of other options:

A/ Use the existing 2.2kW motor with a 1.5kW drive. This limits the maximum current and thus torque / power .

B/ Use the existing motor with a 2.2kW drive but turn the current down. This could be anywhere from 1.5 to 2.2kW. Start low and work up if you find you need more.

No need to change the motor unless it is worn or you want to run it at higher speeds.

A 13A outlet will run a 2.2kW drive. However you should ideally run a dedicated radial (with it's own circuit breaker (MCB)). If on a ring ensure there are not lots of heavy loads on the same ring circuit.
You may also have to change the MCB to a "C" response type. The RCD should also be checked to make sure it is suitable Ideally it should be a A or B type. The common AC type may not work, even for faults elsewhere in the property, due to DC leakage current caused by the VFD.

Robert G8RPI.

I would suggest sticking with the original motor as I have, I run on a dedicated radial. I wrote up a detailed conversion of my M300 in MEW some time ago (2009), using all of the original control functions.

Edited By KWIL on 25/10/2022 09:37:01

I'm not convinced the "original" (existing) motor is original. Looking at the data plate Y/YY and duty cycle, and mess inside the connection box I suspect this has been swapped.

Some M300 were built with your option 2 motor, but the speeds were lower which suggests a different spindle gear box input gear. The low power motor had a much lower top speed.

The lathes .co entry seems a little confusing as it implies to me that the training lathe 'T' version had more power than the normal offering.

Gearboxes are very lossy compared the to belts found in your old C.

I can't really help with the question about the 40% ED only to say that if that's 40% running at full load amps how often would you do that? I don't think I've ever got close to FLA on my M250 and I have taken some serious cuts on it.

Regarding the existing motor maybe your suspicions are correct, mine was made in 1998 and changing the links over to get it in delta was a 10 min job. You might want to consult the Harrison users forum as someone will probably be able to tell you what motor it should have.

I would be tempted to sell some of your motor collection to fund the purchase of a suitable used or new motor.

Curiouser and curiouser. The Y/YY marking means that both low voltage (220 V nom) and high voltage (440 V nom) are connected in star rather than delta / star. I believe there are efficiency and torque gains to be had from this set up.

Relatively low full power duty cycle implies it may be intended for something like an elevator running in short bursts whilst needing plenty of oomph to get things started followed by lower power running to keep things moving.

See the link Ajax posted :- **LINK** , https://www.wat.com.tr/baglanti-en/

but look about three screens worth down the page where it shows the Y/YY links.

A vector drive VFD will work well in low voltage mode. As always vector drive attempts to directly limit the current to that needed to provide only the drive power demanded rather than relying on the motor to self balance forward and back EMF.

Clive

The existing motor would seem to be for the American market, or at least non UK. That style of winding and the 60Hz on the rating plate would indicate non UK. I don’t think you will need to access the star point as the windings can be arranged for 220V as the motor stands.
Mike

I think this is the image to which you refer:

https://www.wat.com.tr/UPLOAD/CONTENT/haberler/resim-8-yazisiz.png

So there is no need to access the star point. Both high and low voltage can be achieved from within the terminal box.

I doubt I will ever approach 40% FL. As previously mentioned, I have no intention of driving this machine hard and now that I have understood the Y/YY wiring options I'm willing to give it a go before considering alternative motors.

I cleaned up the motor last night and will be refitting it later today. I hope to have a VFD fitted later next week.

Yes, you are quite right. I have rewired the connection box (some of the wiring was "shocking" ) after performing an insulation resistance test and checking each of the windings. Should be good to go next week.

Edited By AJAX on 27/10/2022 13:35:42