Puzzle for motor experts

I have a two speed motor, apparently Dahlander wound, with six leads coming out and no documentation of any kind. The leads are two black, two brown, and two pink. I arbitrarily assigned numbers, black 1,2, brown 3,4, pink 5,6.

Resistance readings are-

1 to 2 1.87 ohms

1,3 3.32

1,4 2.96

1,5 1.84

1,6 2.95


2,3 2.96

2,4 3.31

2,5 2.94

2,6 1.83


3,4 1.85

3,5 2.95

3,6 1.84


4,5 1.82

4,6 2.94


5,6 3.38


I want to set the motor up for high speed with a VFD.

It should be possible to discern the connections from these readings.

Bill

You will have to take it apart and ring with a compass... sri...Phil

Phil in Montana said:

You will have to take it apart and ring with a compass... sri...Phil

Click to expand...

Nope, the winding sequence should be possible from the resistance readings/

Bill

I see smoke...Phil

If it is dahlander then draw the windings as a ring with six equal segments.
Three discrete resistance values.

Solution to the PUzzle

No one is going to try, so here is the solution, so simple as to almost be trivial. Note that in the resistance readings 1.85 ohms, give or take a few hundredths, is the lowest reading and occurs 6 times, so it is reasonable to assume that these readings are across one of the six coils. Wire 1 has that reading to wires 2 & 5, so those are connected together at wire 1. Wire 2 shows the low reading to wire 6, so that defines the position of another coil. Likewise,,, we can determine the position of the rest of the coils, yielding the diagram at the bottom. Redrawing to the more familiar delta, we have the upper drawing.

I connected power to 1, 4, & 6 with a three phase Variac to bring the voltage up gradually. I got excessive current, a loud hum, and only slow movement of the motor shaft, just from vibration. Obviously, the coils were bucking, so I moved the power to 2, 3, & 5. The motor came up to half speed smoothly, nearly reaching it at less than 100 volts, what you would expect with an unloaded motor.

I connected wires 1, 4, & 6 together and the motor ran at full speed. That was all there was to it, no disassembly and I don't need no steenking compass, just a Fluke 45 and a Variac.