Chris152 | 13/07/2023 17:50:56 |
43 forum posts 9 photos | I'm thinking to convert our lathe from single phase to 3 phase with an inverter. Top speed on our lathe is 2105; speed on the 4 pole we're looking at is 1400, and the 2 pole is 2800. So far we've not gone beyond the 600 that the slow pulley gives and that seems fine for now, but that may change. |
Thor π³π΄ | 13/07/2023 18:05:25 |
![]() 1766 forum posts 46 photos | Hi Chris, I converted one of my lathes to 3-phase 4 pole motor, using an inverter to supply the 3-phase. The motor I bought can run at both 50Hz and 60Hz so running your motor at a higher frequency than 50Hz should not be a problem. I regularly run my motor over 60Hz, and after more than a decade I have had no problems. A 4 pole motor should be able to give more torque than a 2 pole as long as you don't turn the frequency too high. Thor
Edited By Thor π³π΄ on 13/07/2023 18:09:42 |
Mike Poole | 13/07/2023 18:51:23 |
![]() 3676 forum posts 82 photos | The standard motor for the ML7R is a 4 pole. Doubling the speed using a 2 pole motor could run into questions about the max safe speed of chucks and whether the headstock bearings would be happy, in particular the bronze cone bearing. If you want extra speed the 4 pole motor can be over speeded with the VFD if required but I would be wary about massively exceeding the design speed of any machine. The standard motor for the ML7R is 4 pole and 3/4 hp or 550W. I fitted a VFD to mine and fitted a 4 pole 1hp or 750W motor as I felt the motor would give just a little bit more power at low frequencies but never avoid changing the belt ratios and using the back gear if required. Mike |
duncan webster | 13/07/2023 19:20:30 |
5307 forum posts 83 photos | I regularly run my setup at 75 hz, no issues. I'd go for 4 pole. |
not done it yet | 13/07/2023 20:24:20 |
7517 forum posts 20 photos | Posted by Thor π³π΄ on 13/07/2023 18:05:25:
Hi Chris, I converted one of my lathes to 3-phase 4 pole motor, using an inverter to supply the 3-phase. The motor I bought can run at both 50Hz and 60Hz so running your motor at a higher frequency than 50Hz should not be a problem. I regularly run my motor over 60Hz, and after more than a decade I have had no problems. A 4 pole motor should be able to give more torque than a 2 pole as long as you don't turn the frequency too high. Thor
Edited By Thor π³π΄ on 13/07/2023 18:09:42 I expect the rotor and bearing assembly are likely identical for either the 2 or 4 pole motor, so motor speed will not be an issue with the 1425 motor. |
Steviegtr | 13/07/2023 22:31:09 |
![]() 2668 forum posts 352 photos | Posted by not done it yet on 13/07/2023 20:24:20:
Posted by Thor π³π΄ on 13/07/2023 18:05:25:
Hi Chris, I converted one of my lathes to 3-phase 4 pole motor, using an inverter to supply the 3-phase. The motor I bought can run at both 50Hz and 60Hz so running your motor at a higher frequency than 50Hz should not be a problem. I regularly run my motor over 60Hz, and after more than a decade I have had no problems. A 4 pole motor should be able to give more torque than a 2 pole as long as you don't turn the frequency too high. Thor
Edited By Thor π³π΄ on 13/07/2023 18:09:42 I expect the rotor and bearing assembly are likely identical for either the 2 or 4 pole motor, so motor speed will not be an issue with the 1425 motor. Are you getting confused by the inverter setting for a 50Hz supply or a 60Hz supply as some countries have. Here in the UK you would set the inverter up for 50Hz. The speed settings are a different parameter & in many cases can be set from 0 to over 100Hz. My Myford is set at about 60-65Hz max Which in the right gear runs just over 2000rpm. I would not want to run it at this speed & usualy it never gets taken above 1000. Yes the motor cage is the same for a 2 pole & a 4 pole motor ,so not much chance of doing any damage overdriving it. Definately a 4 pole as the 2 pole will stall out under load. 2 pole motors are usually found on fans. Or any machine that does not require high torque. Steve. |
noel shelley | 13/07/2023 22:55:01 |
2308 forum posts 33 photos | 4 pole , no question about it ! Noel. |
Chris152 | 14/07/2023 07:14:45 |
43 forum posts 9 photos | That's great chaps - I think a decision has been made! Thanks all, Chris. |
not done it yet | 14/07/2023 07:41:13 |
7517 forum posts 20 photos | Posted by Steviegtr on 13/07/2023 22:31:09:
Posted by not done it yet on 13/07/2023 20:24:20:
Posted by Thor π³π΄ on 13/07/2023 18:05:25:
Hi Chris, I converted one of my lathes to 3-phase 4 pole motor, using an inverter to supply the 3-phase. The motor I bought can run at both 50Hz and 60Hz so running your motor at a higher frequency than 50Hz should not be a problem. I regularly run my motor over 60Hz, and after more than a decade I have had no problems. A 4 pole motor should be able to give more torque than a 2 pole as long as you don't turn the frequency too high. Thor
Edited By Thor π³π΄ on 13/07/2023 18:09:42 I expect the rotor and bearing assembly are likely identical for either the 2 or 4 pole motor, so motor speed will not be an issue with the 1425 motor. Are you getting confused by the inverter setting for a 50Hz supply or a 60Hz supply as some countries have. Here in the UK you would set the inverter up for 50Hz. The speed settings are a different parameter & in many cases can be set from 0 to over 100Hz. My Myford is set at about 60-65Hz max Which in the right gear runs just over 2000rpm. I would not want to run it at this speed & usualy it never gets taken above 1000. Yes the motor cage is the same for a 2 pole & a 4 pole motor ,so not much chance of doing any damage overdriving it. Definately a 4 pole as the 2 pole will stall out under load. 2 pole motors are usually found on fans. Or any machine that does not require high torque. Steve. No, I am not. If he was in a 60Hz region, he would have been quoting 1800rpm for his 4 pole motor, not 1400rpm. Neither motor type will/should βstall outβ if operated at less than full load. At least one of my VFDs will operate at up to 400Hz. Some high speed drives use frequencies at those highs. |
Robert Atkinson 2 | 14/07/2023 08:01:57 |
![]() 1891 forum posts 37 photos | I was busy last night and missed this thread: I recently fitted a 3 phase motor and VFD to my ML7 and after asssessing all the parameters I fitted a SIX pole motor and a larger (75mm) pulley on the motor. The motor construction is identical to the two and four pole so is rated to the same speeds. Generally best use is made of a VFD when using it to run the motor at higher than rated (nominal mains frequency) speed. A modern inverter rated 4 motor will typically be good to at least 120Hz and a 6 pole to 200Hz but check the datasheet. A two pole motor is not an viable option for the ML7. It's too fast and less smooth due to increased torque ripple. This can actually be seen in the surface finish of turned items. Robert. |
Robert Atkinson 2 | 14/07/2023 08:25:02 |
![]() 1891 forum posts 37 photos | Posted by Steviegtr on 13/07/2023 22:31:09:
<BIG SNIP>
Are you getting confused by the inverter setting for a 50Hz supply or a 60Hz supply as some countries have. Here in the UK you would set the inverter up for 50Hz. The speed settings are a different parameter & in many cases can be set from 0 to over 100Hz. My Myford is set at about 60-65Hz max Which in the right gear runs just over 2000rpm. I would not want to run it at this speed & usualy it never gets taken above 1000. Yes the motor cage is the same for a 2 pole & a 4 pole motor ,so not much chance of doing any damage overdriving it. Definately a 4 pole as the 2 pole will stall out under load. 2 pole motors are usually found on fans. Or any machine that does not require high torque. Steve. The VFD does not care what the mains frequency is. I think you mean the base or rated frequency of the MOTOR. This is used by the VFD to calculate the correct output voltage for any given speed. If the VFD also allows input of the motor voltage rating you can use either 50 or 60 Hz as long as you also use the voltage for that frequency. If the VFD base voltage rating (not actual voltage) is fixed then you use the frequency for the motor that relates to that voltage. There are two motor damage related limitaions on the maximum speed you can run a given motor on a VFD. First is mechanical and even if it is not stated in the available data a 4 (or 6) pole motor will run at the same speed as a 2 (or 4) pole of the same construction / model. Second issue is voltage spikes and harmonics from the VFD. Modern motors are more resistant to these and "inverter" rated motors have additional insulation. Robert. |
Chris152 | 22/08/2023 14:02:45 |
43 forum posts 9 photos | I posted this question on the FB Myford page but I'm not getting a definitive answer, hope it's ok to repeat the question here. We're putting a 3 phase motor and inverter on our Myford, following an excellent Youtube video on this. I tried to order exactly the same motor as in the video, but the one we've just had delivered turns out to be the TEC T3A (0.75kw, 4 pole), the one in the video is the MS2. The T3A power is rated at 0.75 - 7.5; the MS2 is 0.75 - 37. What will the effect of this be if we go ahead and use the T3A, compared to the MS2? Ours can run at full Super 7 speeds (it's an ML7R), I know that the motor is rated at 1460 rpm, that's fine. Should we just return the motor and change to the MS2? Thanks for any advice. ps This is the link to the T3A: https://tecmotors.co.uk/products/motors/three-phase/aluminium-motors/t3a/0-75kw-4-pole-foot-mounted-motor-b3-ie3/?fbclid=IwAR2GR2W0BNAruBgw3yaTZjjPRUqDLSqHnjpOfmV7KcTdsaIcbfKMrhCeSJo and this is the link to the MS2 (which says on the plate, for VSD use only): https://tecmotors.co.uk/products/motors/three-phase/aluminium-motors/ms2/0-75kw-4-pole-foot-mounted-motor-b3-ie2/ Edited By Chris152 on 22/08/2023 14:05:37 |
SillyOldDuffer | 22/08/2023 14:47:00 |
10668 forum posts 2415 photos | "The T3A power is rated at 0.75 - 7.5; the MS2 is 0.75 - 37" I don't understand the numbers or see them in the spec. Twigged it! It's from the website. Doesn't matter. The T3A series is a range of motors. The smallest T3A is 0.75kW, up to the largest, which is 7.5kW. MS2 is another series ranging from 0.75kW up to 37kW. They both come with 2-4 or 6 poles and with the usual standard footprints The difference appears to be their relative efficiency and power factor - T3A motors are shade better than the MS2, not power or torque, just running cost. On a home lathe, the running cost difference will be tiny. It would show up on a machine that did much more work per day than a Myford. Practically the 0.75kW motors from the T3A and MS2 ranges are almost identical. Either will be fine. Dave
|
Chris152 | 22/08/2023 15:09:25 |
43 forum posts 9 photos | That's brilliant, Dave - I was thinking I'd have to send it back which would be a real pain. Now you've explained it, it's simple and I just completely misunderstood what the range was. Thank you so much! ps I'm correct thinking this'll be fine to work with an inverter, aren't !? The MS2 plate says only for VFD use apparently, our one says nothing about VFD. Edited By Chris152 on 22/08/2023 15:11:25 |
SillyOldDuffer | 22/08/2023 17:08:32 |
10668 forum posts 2415 photos | Posted by Chris152 on 22/08/2023 15:09:25:
... ps I'm correct thinking this'll be fine to work with an inverter, aren't !? The MS2 plate says only for VFD use apparently, our one says nothing about VFD. ... Highly unlikely the motor won't work perfectly with a VFD. Possibly the MS2 is extra well-matched to a VFD, perhaps constructed to give a bit more torque at low speed and to run a little faster than a T3A could. Small differences sometimes matter to industrial users. On a Myford you won't run the motor at top speed in case it damages the bearings, and - if the motor struggles at low speed - torque on a Myford can be got by changing the belt down or engaging back-gear. Dave |
Chris152 | 22/08/2023 17:25:59 |
43 forum posts 9 photos | That's great - thanks Dave. |
Chris152 | 22/08/2023 21:00:40 |
43 forum posts 9 photos | One last question if I may - what amp fuse should I be putting in the plug that'll supply the above setup? (It's a single phase domestic input to a 2.2kw inverter, then on to the .75kw 3 phase motor.) |
noel shelley | 22/08/2023 22:23:53 |
2308 forum posts 33 photos | 10 amp, or 13.. Noel |
Chris152 | 23/08/2023 06:49:38 |
43 forum posts 9 photos | Thanks Noel. |
Robert Atkinson 2 | 23/08/2023 07:50:50 |
![]() 1891 forum posts 37 photos | While Noel's answer isn't wrong per-se, he does not have the required information to determine the fuse size required. The fuse in the plug is there to protect the cable. So to know the rating you need to know the size of the flexible cable used. If a 13A fuse is fitted then 1.25mm2 or 1.5mm2 flex must be used. If 1mm2 flex is used then a 10A or smaller fuse must be fitted. Robert. |
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