16-04-2012, 09:02 AM
Hi,
You are most welcome Rob and I'm happy to have helped in some small way.
Although I worked at Brook Motors for 24 years I was involved in logistics so all my knowledge of the electrical side is self taught. As an apprentice mechanical engineer at the NCB I was on a six month training course at Crigglestone Colliery near Wakefield and I did so well that I completed the course early and was allowed to wander over to the apprentices in the electrical section; I was taught how to wire a 3 phase motor but apart from this I've picked up information as required over many years.
Modern six wire 3 phase motors are easy enough to sort out even if every connection is lost but a single phase motor that is old and been played around with is a totally different matter. Many have a centrifugal switch that drops the start winding offline once the motor reaches about three quarters full speed allowing the motor to induction run. However on an unknown single phase motor without circuit diagram the motor could be cap start/induction run or even cap start/cap run. A further problem with caps is trying to sort out the correct uF value.
As I explained to Rob the best place to start with an unknown single phase motor without circuit diagram is to disconnect all the wires after first marking them and drawing a sketch of the connections. Then take continuity readings on all the pairs of wires; with luck two pairs should give a reading these being the start and run windings; the start winding will have the highest resistance reading so these are marked "Start winding" the other pair with the lower resistance reading are marked "Run winding". I'm hopelessly colour blind so I simply arrange the connections to suit me but A1 is Live and A2 is Neutral. (Modern are U1 Live and U2 Neutral).
With the run winding wires connected directly to A1 & A2 supply these can then be ignored. The Start winding needs tracing through as the centrifugal switch needs connecting in "Series" with the winding then with the switch connected the two loose wires are connected to A1 & A2. At power up the run winding is energized and remains online whilst the power is on but the start winding becomes energized at power up only until the motor reaches about three quarters full speed then the centrifugal switch opens and drops the start winding offline allowing the motor to run on its run winding only. This is in very simple terms but is a good basis to work from.
I always find it difficult trying to help in offering advice to a friend some distance away using emails because with a motor on my bench I can experiment and see what I have got but I've seen many motors with other components attached; not only caps but heaters;thermistors; thermal protection; thermal detector; magnetic brake and reversing connections to name a few. Fortunately most of the small common old single phase motors are like Rob's with just the two windings and a centrifugal switch making them easy to sort out. If continuity cannot be found on two pairs of wires then I would assume the motor is not worth any further investigation and scrap it; these fractional horsepower motors are cheap and plentiful.
http://ecatalog.squared.com/pubs/Machine...CT9201.pdf
I'm certainly no expert on motors but I can usually get them running and just for interest please check out the above site; it's enough to put anyone off even looking at a motor.
It's time I cracked on with the decorating. Good luck with the lathe restoration Rob and I'm here if you think I can assist further; please keep me posted.
Kind regards, Col.
You are most welcome Rob and I'm happy to have helped in some small way.
Although I worked at Brook Motors for 24 years I was involved in logistics so all my knowledge of the electrical side is self taught. As an apprentice mechanical engineer at the NCB I was on a six month training course at Crigglestone Colliery near Wakefield and I did so well that I completed the course early and was allowed to wander over to the apprentices in the electrical section; I was taught how to wire a 3 phase motor but apart from this I've picked up information as required over many years.
Modern six wire 3 phase motors are easy enough to sort out even if every connection is lost but a single phase motor that is old and been played around with is a totally different matter. Many have a centrifugal switch that drops the start winding offline once the motor reaches about three quarters full speed allowing the motor to induction run. However on an unknown single phase motor without circuit diagram the motor could be cap start/induction run or even cap start/cap run. A further problem with caps is trying to sort out the correct uF value.
As I explained to Rob the best place to start with an unknown single phase motor without circuit diagram is to disconnect all the wires after first marking them and drawing a sketch of the connections. Then take continuity readings on all the pairs of wires; with luck two pairs should give a reading these being the start and run windings; the start winding will have the highest resistance reading so these are marked "Start winding" the other pair with the lower resistance reading are marked "Run winding". I'm hopelessly colour blind so I simply arrange the connections to suit me but A1 is Live and A2 is Neutral. (Modern are U1 Live and U2 Neutral).
With the run winding wires connected directly to A1 & A2 supply these can then be ignored. The Start winding needs tracing through as the centrifugal switch needs connecting in "Series" with the winding then with the switch connected the two loose wires are connected to A1 & A2. At power up the run winding is energized and remains online whilst the power is on but the start winding becomes energized at power up only until the motor reaches about three quarters full speed then the centrifugal switch opens and drops the start winding offline allowing the motor to run on its run winding only. This is in very simple terms but is a good basis to work from.
I always find it difficult trying to help in offering advice to a friend some distance away using emails because with a motor on my bench I can experiment and see what I have got but I've seen many motors with other components attached; not only caps but heaters;thermistors; thermal protection; thermal detector; magnetic brake and reversing connections to name a few. Fortunately most of the small common old single phase motors are like Rob's with just the two windings and a centrifugal switch making them easy to sort out. If continuity cannot be found on two pairs of wires then I would assume the motor is not worth any further investigation and scrap it; these fractional horsepower motors are cheap and plentiful.
http://ecatalog.squared.com/pubs/Machine...CT9201.pdf
I'm certainly no expert on motors but I can usually get them running and just for interest please check out the above site; it's enough to put anyone off even looking at a motor.
It's time I cracked on with the decorating. Good luck with the lathe restoration Rob and I'm here if you think I can assist further; please keep me posted.
Kind regards, Col.
Happiness is a wreck of a cabinet to restore.
