I'm preparing a series1 (BOSS) Bridgeport to fit PC-based controls. The main spindle motor is a US motors 2hp, & though the rating plate gives a connection diagrams (9 wire) for 220 and 415 volts there are actually just the 3 wires coming from the coils and I believe it was set for high voltage. I want to run it from 240Volts via an invertor. I'm going to see if I can unearth the actual winding terminations, but if I get too far out of my depth it'll be off to the rewind shop on Monday for them to do it. My question is, as understand it the US style 9-wire dual voltage motor is star connected for both voltages. More usual here in the UK is 6 wire, with star connection for high volts & delta for low. If it looks easier to reconnect this motor for delta than to unearth all the terminations to parallel the windings, will that be just as good?
Wires 7,8 & 9 are a star connected 220v 3phase winding. The star point is not brought out but buried in the windings
1 & 4, 2 & 5, 3 & 6, are three separate 220v windings.
For the high voltage connection
Link 4 to 7 5 to 8 6 to 9 Power in to 1,2 and 3
For the low voltage connection
Link 4, 5 & 6 - this a second star point and left floating
Power in to linked 1 & 7 2 & 8 3 & 9
The change to low voltage is straightforward if the wires are properly marked but if they are not identified it is still possible to sort it out.
Separate all the wires BUT MAKE A NOTE OF WHICH WIRE WAS CONNECTED TO WHICH. Identify the star winding by checking for continuity between 3 wires.
This star winding is a low voltage three phase winding in its own right and the motor can operate normally up to rather more than half its rated power on this winding with no connection to the remaining windings.
Identify the three pairs of wires which are the connections to the remaining windings Link together the three ends that were originally connected to the star winding. The three unconnected wires are now power in to a second three phase star winding.
Run the motor with power in (suitably fused!) to only ONE star winding and note the direction of rotation.
Repeat with power in to the second star only. If it gives the SAME direction of rotation you have the correct connections and it is now safe to parallel the three outer ends of the two stars for full power operation.
If its the wrong direction, correct by reversing any pair of wires on one of the stars.
All the above applies to the 9 wire motor connections indicated on your nameplate. The remaining wires are probably tidily inside the motor housing and this is the safest way to go. Star to delta conversion is possible but it would mean diving into the winding to disinter the star point and the voltage change ratio would be root3:1 rather than 2:1.
I obviously didn't explain the problem very well (you're not the only one who missed the point of the question )
My point was that, although the *rating plate* refers to a 9-wire setup, and actually has diagrams of how to set the links for high & low voltages, in reality the *windings* have only 3 wires coming from them so I had to dig deeper anyway. What I wanted to know, in part, was whether digging out the star point so as to reconnect in delta would be just as good for my purpose as extracting all the links so as to parallel the windings.
In fact, having done some digging and found the star point, there is no sign of the other links. My guess is that the motor has been rewound at some time in its life, & the rewinders have saved a few bob by dispensing with the dual voltage facilkity. GRRRR!
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