Thread: Hercus 260 - To convert to 240 Volt, or not

Hi folks, I'm a newbie to this forum so hope you can help.

I've just bought an ATM260 - ex training school machine, currently powered with a 1/2 HP 3 phase ASEA motor. I've been wresting with what to do about the 3 phase motor; ie either convert to a 240 volt 3/4 or 1HP CMG motor (I have both) which will require a fair amount of modification, or look at installing a converter; ie 240 volt to 415 volt 3 phase.

Would like to gauge what others in the forum have done. Must admit, I'd rather not change the existing motor, but I'm prepared to do it if the option of power conversion is too expensive.

Would really appreciate your input and advice.

Just a bit of background as to why I chose the Hercus - I had a technical education when I was young, attending a Technical school for my secondary education. As part of the trade training, we were trained in woodwork, sheetmetal work and turning and fitting. The Hercus was what we used for the latter, so after all these years, the wheel has turned a complete 360 degrees. Can't wait to fire this little bloke up and make the first cut ...

Bad luck you didnt have a 1/2HP cmg or could get one as the motor mounts for the asea that might be on it and the cmg are almost ideal.

Buy a VFD (Variable Frequency Drive). It can run your existing 3-phase motor from a single phase 240V powerpoint. On top you get variable speed and soft start and fast braking etc etc. Ask your local electric motor dealer for a low cost VFD, or look up eBay for VSD or VFD (all the same thing).

Maybe you already considered a VFD, but think a 1/2HP motor is on the weak side for a 260. In my experience, on a machine tool a 1/2HP 3-phase motor is about as useful as a 3/4HP single phase motor, but runs smoother and quieter and vibrates much less. If most things you do is small diameter work of say under 60mm diameter, 1/2HP is fine.

But if you do a lot of large diameter work, you may want more power. I suggest in this case you buy a 1HP VFD, that way if you later want to upgrade to a larger motor of 3/4 or 1HP, it will be an easy motor swap only.

The 260 was originally sold back in 1988 with the 1/2HP 3-ph TEFC motor as standard. The 3/4HP 3-ph motor was $39 extra, the 1HP 3-ph motor was $55 extra. There were also single phase motors of 1/2HP and 3/4HP available at extra cost. I mention this so you know this lathe should handle sizewise these motors without too much problems. Chris

It is just as cheap to buy a VFD as a single phase motor, while the single phase motor will be slightly cheaper by the time you have to buy new contactors they will be similar in price...

i might be biased 1hp motor with vfd= forward /reverse/ variable speed / jog+ numerous other options
before you go down the 3 phase motor path check to see if you can change the motor wiring to delta
i replaced motor with one from from a machinery wrecker/ dealer for 20 dollars theyre usualy only scrap value the base plate may have to be redrilled and tapped to te new motor mount
john

I'm looking at going down this path myself. I have 3 phase power and a 3/4hp 3 phase motor, but I would like speed control. All the VSDs seem to have a jog function. Can someone please explain how this function is used on a lathe? One of the VSDs I'm looking at only has 4 logic inputs. That would be start, stop, fwd/rev and either jog or emergency stop. So I need to decide between jog or e-stop.
Cheers,
Chris

Another vote for VFD, they are around $100-$150 posted for this size on ebay. Do a search on this site and you will find loads of info and lots of people willing to help out if you get stuck on anything.

Dave

Thanks to everyone who's replied - it's very much appreciated. I'm now thinking I'll stick with 3 phase, maybe upsize to either 3/4 or 1 HP - thanks for the background info on the higher powered later models, Chris - and therefore go the VFD route. It would be good to have that flexibility of increased work size and variable speed. A bit of research on ebay as suggested Dave J has opened a whole new world ! Thanks.

Must say it's interesting to find such an active metal working forum on a woodworking site ! Hope I can contribute something in the future.

Originally Posted by jack620

All the VSDs seem to have a jog function. Can someone please explain how this function is used on a lathe? One of the VSDs I'm looking at only has 4 logic inputs. That would be start, stop, fwd/rev and either jog or emergency stop. So I need to decide between jog or e-stop.
Cheers,
Chris

As far as I can tell, the jog function is useless on a small lathe, since it is easy to fine position a chuck by hand if required. It may be useful on a larger lathe where the chuck weighs alone 50 or 100kg and is hard to rotate by hand.

By the way, you only need two of the logic inputs for start/stop/forward/reverse. That is unless you want to wire it up by the 3 wire method, then it needs 3 logic inputs. The 3-wire method has the advantage to be failsafe against the breakage of one of the three wires. This added safety may be important in a large lathe used in a factory, it is pretty much irrelevant for a small lathe used only at home.

Chris

I have suitable cheap VFD's, see the classifieds as I had better put the advert in the correct place. You will have to re-wire the motor to 220-240 volt which should not be a big issue.

Just a heads up regarding a suitable VFD. Most people here possibly think of them as a single to 3 phase converter with benefits, and that's true. However it is more accurate to really think of them as a motor controller. The reason I mention this is because the VFD and motor should be matched in size, so don't go buying a 1 HP VFD when you have 1/2 HP motor, they aren't correctly matched. The VFD can normally control a motor one frame size up or down from its rated capacity, but that's it. While a gross mismatch will probably still work, the emphasis is on probably, as you aren't running the VFD as the designer of it intended. The VFD expects the motor of a certain size to have predictable characteristics, and when one of a different size is coupled to it, it won't have those characteristics. What will happen? Who knows. So if you have a 1/2 HP motor, buy a 1/2 HP VFD. If you want to later change the motor, you also change the VFD.

As far as star and delta configurations, ALL motors can be converted to delta, however they may not be wired to do so from factory. I have 3 Hercus machines running VFDs, and if I recall correctly none of the standard motors were wired for delta. However it's just a matter of digging out the star point on the motor windings and rewiring the motor. I did mine myself, however have a background in this area, a motor rewinding service will charge about $60 for that job, and it's a very easy job for them to do.

I would definitely recommend a VFD over changing the motor to single phase.

Pete

Pete, I am a bit puzzled by what you are saying.

You say don't buy a 1hp rated VFD and couple it to a 1/2hp motor, but you are also saying that you don't know what will happen if you.

But you are also saying that a VFD can handle a motor 1 size up or down from its' capacity.

Aren't those two statements contradictory? Or do I misunderstand what you are saying?

Say I have a 2hp motor, you say I shouldn't buy a 3Kw/4hp VFD?

Pete, it is generally a good idea (if cost permits) to choose the VFD one or two sizes larger than the motor. Every VFD can easily be programmed to run a smaller motor, usually simply by entering the motor name plate values. These are the advantages of choosing a VFD larger than the motor:

- no derating necessary when running the VFD at its highest chopper frequency (the highest chopper frequency is where you hear the least "singing" noise, you usually want to use the highest frequency but often cannot because it derates the maximum motor power that the VFD can drive).

- the VFD will heat up less in operation. Cooler electronic components last longer. You can be less careful with cooling when designing the enclosure for the VFD. And remember that VFD's need to be derated when running hotter than designed.

- especially on a lathe, you will enjoy more dynamic braking capability from a larger VFD. You can brake a heavy chuck/workpiece with lots of inertia faster, without having to add an expensive external braking resistor. If you use a VFD of same rating as the motor, It is not uncommon for a lathe to cause the VFD to trip out with heavy chuck/workpieces. To avoid this tripping, you have to change the VFD progrtamming to use a slower ramp-down time, say 5 or 10 seconds instead of 1 or 3 seconds.

- a larger VFD may remain useful if you decide to upgrade to a larger motor.


The opposite, eg using a motor larger than the VFD, is a very poor choice. It is true that almost each VFD is capable of driving 150% of its rated power, BUT ONLY FOR ABOUT 60 SECONDS, then the VFD overheats and its processor automatically throttles the output power down. You end up running the VFD constantly at its upper temperature limit, and you have to constantly use the lowest chopper frequency which can be very lound and annoying to your ears. Plus dynamic braking will be very poor. Avoid this scenario. Chris

A VFD is generally matched either in horsepower or current to the requirements of the motor, if greater braking potential is required then external resistors are added. This is what the manufacturers I have read have recommended. I would be very interested if others here can point me to manufacturers' data where they suggest running a VFD much larger than the motor size. I have 3 SEW Eurodrive VFDs on my machines and am about to order 3 more, and can assure you they will only accept data for motor frame sizes one size up or one size down from their recommended rated size. When programming they simply cycle between the 3 possible motor sizes. Now that's not to say they won't work with much smaller motors (and that's precisely what I intend to do with 2 of my new drives), they possibly will, however that is not the way they are designed to operate.

I believe the reason for the above is because a motor is not a resistive load, it forms part of a network to form the sine wave (incidentally that is the crux of the reason as to why motors should never be switched out of circuit when operating). The VFD expects a certain type of load as defined to it. However the other reason is that, as I have often said, these are motor drives and not simply single to 3 phase converters. The drive is also there to protect the motor from overload. If it believes it has a 1.5 KW motor hanging off it and it is fact only 0.75 KW it will not protect the motor correctly.

Again, I'm happy for somebody to point to manufacturer's data that claims gross mismatches are fine, however I would suggest a correct match is how the manufacturer designs them. However I should also add they specify inverter rated motors and correct cabling too, neither of which I personally use, nor do most guys in their home shops from what I've seen. However that doesn't make it right, and it may potentially lead to more difficulties further down the track, particularly for those who aren't comfortable working in this field.

Pete

Hi Pete, I do not know your particular make. But I run five different VFD's on lathes, mill and drill and saw (Lenze, Siemens, Telemecanique and on the 260 Omron/Yaskawa). Each of these can be set for any motor power up to the max rating of the VFD. Not in fixed steps or frame sizes, but really freely selectable in random kW and Amps. Except the older Lenze (10 year old) which is not Vector technology, they can all also measure the motor at hand and calibrate themselves to match it. It is perfectly normal to use one or two sizes larger VFD's. The manuals even show how to run several (two or three motors) from the same VFD, however in this case one looses overcurrent protection and one cannot run in Vector mode (it is fairly common in HVAC applications of pump application to run several motors from one VFD). If you want to, I can point you to some links to user manuals that explain this.

Modern VFD's (say less than 10 or 15 year old) do not expect anymore a specific motor size, but can handle a very wide range of motor powers and makes up to the VFD's maximum rating. 2, 4, 6, pole motors, inverter rated or not, even special high speed motors that can run at up to 400Hz are usually not a problem at all. Older VFD's that did not yet use microprocessors were as you say only adjustable in fixed steps, or were made for a specific brand and type of motor.

Hope this info helps. A VFD is in my opinion really the most useful single mod that one can add to a lathe. Chris