Ted.
Wecome to the forum, nice to see another Brit!
What our American friends like to do is bring a lead off some of the coil ends internaly, then make some or all, depending on the winding design, of the inter-coil connections inside the terminal box. On the otherhand we in Europe generaly make all the inter-coil connections internaly and bring just six leads out of the winding to allow for star-delta starting, or three leads out if the winding is suitable only for DOL starting with the star or delta connection made internaly. The six leads are the start and finish of each of the three, phase circuits and each circuit may be made up off several coil groups, not just one. Machines with 12 leads out are very rare in the UK and you are unlikely to come across one unless you work with machinery imported from the States or Canada. They tend to burn out relatively quickly because of the diffences in supply voltage and frequency but the winding design can be modified slightly by making alterations to the cross sectional area of the wire and the number of turns in each coil to allow for these differences when the motor is rewound.
You do not have just three coils in the motor. Starting from scratch you have one phase that has two groups of coils. One group is the North and one is the South. Each group has a start and finish lead. Multiply two groups by two leads you now have a total of four leads.
Making the motor three phase means you now take the two groupsmultiplied by the two leads multiplied by three phases which now gives you a total of twelve leads!
To elaborate on Steves comments.... The connection that is required between the North and South coil-groups is made internaly on European manufactured motors and its integral with the winding. On a 12 lead design the connection is made by bringing leads off the coil-group ends and making the required connection externaly and away from the winding, usually in the terminal box. This is done for each of the phase cicuits.....hence the extra 6 leads.
hi, I'm new in forum and don't speek english wery well,sorry! If motor has 12 lead, maybe this is making for
speed control -two fixing speed with three phase motor or 6 fixing speed with one phase. They have the old motors with meny poles and coil.
I would say the most common use of 12 leads is to get 3 phase dual voltage motor with the capability of wye/delta starting. Most common 3 phase dual voltage motors in US that I have seen are 9 external leads with wye made up of 10,11,12 internally. (208,230/460 V ac) No way to connect for a delta with that, but if you bring them out, then you can do parallel or series, wye or delta. 6 leads works for wye/delta, but is dual voltage only with voltages V1=V2(1.732), not V1=V2(2)
I doubt anyone would commonly bring out leads for one pole separately from its opposite. I believe it is useless if it is connected incorrectly unless maybe you are wanting to make a consequent pole motor to run 1/2 speed.
The twelve wires minds the 3 Phase Squirrell cage Induction motor can work for two voltages, in america usually 460/230Volts and in europe 220/380 Volts.
This design is made with the prime objetive for the starting´s motor usually the motor can be started with star-Delta in both voltages,also you could start the motor in Part-Winding.NEMA-STANDARDS use Numbers to mark the wires from 1 to 12. In a Three Phase motor the wires in Phase a are labelled like 1-4-7-10, phase b: 2-5-8-11 and phase c: 3-6-9-12 in Europe the leads are labelled under IEC Standard and Phase a : U1-U2-U5-U6 Phase b: V1-V2-V5-V6 and Phace c: W1-W2-W5-W6. If you perform the right connection then the motor will run well.
