trying to understand starting options in particular
|Kevin Cobley||31/03/2021 14:23:09|
|17 forum posts|
I have recently acquired an Elliott 2GS Pillar Drill, which I need to convert from 3 phase to single phase. Whilst I understand a fair bit about how motors work, I'm still not sure what my options are regarding start capacitors and switch-gear etc.
The machine has a built in forward / reverse changeover switch which ideally I would like to continue to use. What's the usual practice for this type of replacement - do I need a motor with centrifugal switch - can I avoid any further switch-gear to start the motor?
Given that the pulley is 5/8th diameter shaft mounting, I suspect I may be limited to older motors as new ones seem all to be 14mm or 19mm shaft diameter.
Thanks for any advice,
|Kevin Cobley||31/03/2021 15:01:31|
|17 forum posts|
Re-reading my post, I ought to mention that I'm expecting to replace the motor entirely, not re-use the 3-phase motor.. so easy to miss the obviously required info
|Thomas Cooksley||31/03/2021 16:47:17|
|55 forum posts|
Hi Kevin, there are several other factors to take into consideration. Not least the power of the motor and the way the motor is mounted. You say the shaft is 5/8th inch, that suggests that the motor is an imperial one. The power will most likely be in horse power (hp) and the fixing holes will be in imperial dimensions. There are still imperial motors available but I don't know how easy they are to get hold of. You may be able to make a metric motor fit but you may have to make an adaptor plate and then either alter the bore of your pulley or the diameter of the shaft to fit. As far as the control gear is concerned you may be able to retain some of it but until you have your new motor and it's wiring diagram you won't know. Any contactor coils will be 400 volt and these will need to be changed to 230 volt ones. I would price up the cost of fitting an inverter to the original three phase motor instead, it may prove to be cheaper than fitting a new motor. Hope some of this helps, any questions feel free to ask. Tom.
|Kevin Cobley||31/03/2021 16:53:58|
|17 forum posts|
Yes, ofc, forgot to mention that the original motor is 3/4HP (550W in modern parlance). It has the foot type of mounting that seem fairly universal - 3 inch wide, four screws.
The Pulley doesn't really have any meat for boring out, especially for 19mm shaft. Hadnt considered turning down the shaft of the motor - interesting.
|Ian Parkin||31/03/2021 16:55:20|
1021 forum posts
Once you have used a drilling machine with variable speed you would never go back to a belt change type.
I’d agree with thomas fit an inverter for about £100 all in you wouldn’t regret it
keep your original motor and go from there
|Thomas Cooksley||31/03/2021 17:08:13|
|55 forum posts|
Hi Kevin, You should have some form of control gear that is held closed by a coil, to provide a no volt release. This prevents the drill automatically restarting after a power cut. Don't forget if you turn down the motor shaft it will most likely make any warranty invalid. I have just been looking through April's MEW, it may pay you to contact someone like Newton Tesla they seem to specialize in just what you are trying to do. Best of luck Tom.
|Dave Halford||31/03/2021 17:27:00|
|2052 forum posts|
The foot mounting varies in size, these are all to a standard regardless of motor type and the specs are readily available. (check out the photos)
You just need cap start motor, they come with the centrifugal switch and are reversable if you wish.
There would appear to be plenty of 2nh hand single phase motors judging by the urge to go 3phase.
|Kevin Cobley||31/03/2021 22:04:57|
|17 forum posts|
Yes a zero volt switch will be added and also an emergency stop. It has neither at the moment.
I'm curious about these £100 inverters. Whenever I looked they were much more expensive than that, at least for reputable brands. Some of the cheapo ones have very bad EMC, and what looks like inadequate heatsinking. If you can point to a good model at £100 then maybe its worth it, but from what I see a single phase motor will cost less.
Thanks for the sizing information. I checked and mine is 3in. by 5in. which doesn't fit any of those sizes. So it looks like something older is the only way? Any good places to look other than the usual auction site?
|2426 forum posts|
Are you certain the existing motor is not dual voltage 380/220v, to be sure check inside the terminal box for number of connections.
|not done it yet||31/03/2021 22:36:14|
|6812 forum posts|
It is a drill. Why would you need to operate counter clock-wise? I do have left-handed drills which I can either use with my mills or hand-held drills (used as screwdrivers), but they are for special jobs...
There is no way I would change out a three phase motor for a single phase one, if at all avoidable. VFDs are cheap, reliable and offer so many advantages over single phase equivalents.
|Kevin Cobley||01/04/2021 09:00:58|
|17 forum posts|
Thanks forasking about the voltage - the label states 415-440V so it would need a step up VFD.
This model drill press has back gear for slow speeds, so could be used for tapping etc, which is why it has reverse.
|john fletcher 1||01/04/2021 10:21:23|
|794 forum posts|
Kevin it is usually very easy to alter the connections in the motor terminal box, to reconnect the motor from 415 volt STAR to 240 volt DELTA. Please send a picture of the terminal box with the lid off and then I/we can put you in the picture. It is not so difficult to alter the motor internally, but it will need dismantling completely. In the past some on posted a some excellent picture on 'HERE' showing how he carried out the conversion, might be worth a look.
I met a friend for the first time in 12 months on Tuesday morning, and he showed me an inverter which he recently bought via ebay for £45 and it came from London. Frequently there are discussion on this site regarding the quality of inverters from China, I've asked several times, has any one actually seen or know of a faulty one, up to date no reply. I just like to see fair play, and no link to PRC either. John
|John Haine||01/04/2021 10:46:00|
|4675 forum posts|
Less than 65 squids.
I do have a spare 3/4 HP single phase motor as it happens, off the Myford VMB that I fitted with a 3-phase motor.
How long do you run a drill in one go, a minute or so max? I doubt EMC will be a problem.
Slow speed and reverse are wonderful on a drill, for tapping!
|Nigel McBurney 1||01/04/2021 10:46:57|
1000 forum posts
I bought new in 1968 a Fobco 1/2 inch dril it was fitted with a simple on /off rotary switch and 1/3 hp single phase motor ,I fitted an MK 13 amp plug to the lead and its been like that ever since,In those days there were no labels stuck every where eg no volt release must be fitted,and in reallity a no volt release is not really required,if theres a power cut and I did forget to switch the drill off so what ,it may start up again when powers restored so what. My Myford runs with a 3/4 hp s/p motor and that is started with a 13 amp plug in an MK metal clad socket,never had a problem it says something for MK that the switch is still working after 52 years. I expect I will get a barage of replies about safety but just consider this aspect of safety ,I expect many home worshops have electric heaters up to 3 kilowat,phase convertors,electric welders,do these have no volt release switches ? Any of those left on after a power cut could cause a fire if a fault developed ,in my view far more dangerous than a drill left running particularly if the workshop is attached to the home. The one safety feature I do have is a safety light which comes on via an internal battery when the power fails,which is quite often in a very rural area,and then it is really dark in my workshop.So to remotor a drill just fit a single phase capacitor start motor as others have said advertise for a suitable motor as there must be more about now due to others converting to VFD.I have never had a requirement to for a reverse function,occasionally when there has been a need for power tapping say fifty holes I use a commercial tapping head in my larger Meddings drill which has its own internal reversing mechanism.
|John Hinkley||01/04/2021 11:10:49|
1332 forum posts
There's no need to worry about boring pulleys or reducing shaft sizes on whichever motor you fit. I have successfully used pulleys with the Taperlock system, like these. Having said that, I'd go with the majority and recommend a VFD for the versatility and control it will give.
|Martin of Wick||01/04/2021 12:31:26|
|249 forum posts|
| Kevin it is usually very easy to alter the connections in the motor terminal box,
....Yeah well maybe..... if you are lucky and the motor is configured that way. With older motors, I have found that they tend to have been designed for industrial use and be single voltage star connected without the facility for alternate connections in the junction box. If you want to re configure these type motors as delta you will have to dig around and find the star connection point in the windings - and even if you can get at that easily, you have to consider whether the wire grade used is suitable for higher currents (probably ok for a drill).
Like the OP, I acquired an old Denford, couldn't re-configure the 3P motor as the star point was not accessible without potential damage to an otherwise excellent motor and resorted to a cheap and nasty step up inverter (250 to 380v which works fine). Slightly scary as you have upwards of 380v floating about at the back of your drill, so need to use a bit of care when wiring up.
Choices for the OP...
It is probably quite a good motor so if you can reconfigure the old motor to delta easily, use a low cost 250v single to 3 phase inverter.
Otherwise if comfortable with higher voltages in your workshop, use a more expensive 250 to 380v inverter.
Otherwise, you can obtain imperial B56 frame motors from Newton Tesla (at a price).
Otherwise you are in the realm of searching on line markets, for S/H imperial single phase (usually split phase start windings with centrifugal switch) . Check specs and motor plate carefully!
or go down the route of adapting a cheap metric capacitor run motor (at 550w usually 80 frame size so 19mm shaft, but I did once see a 71 frame with a more convenient 14mm shaft).
|Kevin Cobley||01/04/2021 14:36:02|
|17 forum posts|
Unfortunately, as Martin suspected, the motor only has three studs in the connection box, no star point. So this would make a VFD un-economical , I think. This is kind of where I came in.
Thanks for the taperlock link. In this case it'd be going from 14mm to 5/8ths, so I don't think there will be space as their OD is 35mm unless I've misunderstood how they're meant to work.
An EMC can be an issue - a friend of mine fitted a chinese VFD to his lathe only to discover that the electronic LED light controller next door went completely haywire when he used it - he described it as a lathe controlled disco light. His neighbors were not impressed - inside there was no filtering on input or output - this is how they undercut the competition. Still had all the badges, but ofc just meaningless.
Anyway - sounds like an older cap start motor with centrifugal switch is what I need to find then.
Next thing to sort out on it is how to get the gear lever off - the short taper pin is stuck tight and I cant clearly tell which end is which..
|Alistair Robertson 1||01/04/2021 15:07:33|
|145 forum posts|
I bought a Warco bench drill (single phase) and I wasn't very happy with the smoothness when it was running so I fitted notched belts which was a great improvement but not perfect. A new 3 phase motor and a VFD absolutely transformed the drill with almost no need to move belts about. From 55 rpm to 2500 rpm with only one belt change. I would think a VFD is the only way to go. Some suppliers are now selling drill to this spec. but they aren't cheap.
|not done it yet||01/04/2021 15:22:14|
|6812 forum posts|
There are two other alternatives available.
(1). Accept a lower output power and run your star motor on a 240 volt output VFD, or
(2). Source a 415V 1HP motor and run it on a 240V output VFD.
Unless you are tapping huge holes, you are unlikely to need more than 300W for tapping but power would be down to about 40% for alternative (1). Alternative (2) would only derate the drill power by ~20%.
I’ve rewired two motors from star to delta, by splitting the star point, this year. It is generally a not too difficult job, although some motors may need a modicum of care to locate suitable points for connections, if the star point has been heavily varnished to the windings.
Other odd sized motors are occasionally available (one of those I recently converted to delta was 1.25HP). That motor would provide ~ 3\4HP if run in star confiuration with a cheap inverter.
As you are wanting to reverse for tapping, a VFD can be reversed directly (while running) from a single control switch/button - and with no capacitors to stress (with multiple starts).
|Mike Poole||01/04/2021 15:55:01|
3343 forum posts
A centrifugal switch will be an irritation as the motor will need to coast to a low enough speed for the switch to reclose before the motor can be reversed. It would be worth using an inverter if the star point can be split as the motor can be made to reverse very quickly if suitable ramps are programmed. There is a limit to how fast an inverter can slow the motor as power is pushed back into the inverter and if the DC link voltage rises too high it will fault. Some inverters can use an external resistor to dump the power and implement some very sharp stops. If you are interested in power tapping then I suspect you may have lots of threads to make and notice should be taken of the number of starts per hour recommended for the motor.
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