Two speed 3 phase switch 2

[MichaelSutten]

I have a Maskinner milling machine.
It has a two speed switch.
It operates on 3 phase 380 volt.
It was working well. then the switch started to drop a phase.
If i re-switched the switch it would make contact and run perfectly again.
I decided to replace the switch before the motor became damaged.

Being in a maintenance environment (im making excuses here) i got distracted before labeling the wires or the switch.
Now i have a problem installing the new switch i have purchase or even ensuring it is the same as the original.
The new switch is a rotary off/star/delta configuration.
The original switch was a slow/off/fast configuration.
i am presuming that it switched the motor from star to delta.
The speed diagram printed on the machine indicates that slow is half the speed of fast.

It is not easily possible to access the motor itself and i cant see the normal terminal box and bridges.
I have six identical looking wires which i have labeled arbitrarily one through to six.
The resistance across any pair is as follows:
1-2=20 2-3=13 3-4=20 4-5=20 5-6=23
1-3=23 2-4=23 3-5=20 4-6=13
1-4=13 2-5=13 3-6=13
1-5=13 2-6=20
1-6=20

I have tried all possible configurations in star and delta.
that was a tedious exercise but yielded some results at least.
The only configuration that allowed the motor to run quietly (my only sure test that things are OK)
was in star with lives connected to 1/2/6 and 3/4/5 bridged.

i mistakenly thought that having found the star configuration that the options for delta would be easy to find.
i tried again all possible remaining configurations for delta but the motor made excessive noise on all of them.

please could somebody help or do i accept that i now have a single speed machine.

Michael Sutten
Cape town South Africa

 

[ScottyUK]

What you have is probably a Dahlander connected motor. If you Google [blue]dahlander motor switch wiring[/blue] and look in the images tab you'll find a few examples which should help you work out how the switch was connected originally. It would obviously help if you know the motor connections because you're going to need to make sure the windings are correctly grouped by phase and polarity. Awkward or not I think you're going to need access to the motor terminal box.

 

[Parchie]

@Michael,
It's good that you have managed to run your motor at high speed (T4, T5, and T6--> supplied; T1,T2 and T3 joined). To go low-speed, you need to connect T1 to line 1, T2 to line 2 and T3 to line 3; leave the other three lines (T4, T5, T6) open.

 

[MichaelSutten]

Thank-you very much ScottyUK and Parchie for your help.
seems like you were both 100% correct. my mill now has two electrical speed settings.
Just need to install the switch and i can close it up for another 10 years.

 

[ScottyUK]

Glad to help - thanks for the feedback.