Table saw motor wiring

polaroid · Jul 1, 2021

Hello people. My old man has a table saw and water has got in the switch, he decided to remove it ready for me to replace and due to poor memory can't remember how it was wired up.

I've not had much experience with motors etc but from what I can work out it's wired as follows:

[ElectriciansForums.net] Table saw motor wiring

I haven't checked the windings but these are the connections - the nice bright white cables are the capacitor:

I've got a new NVR switch so I assume it's N = 0v and BR & BL = 230v?

From what I see online it's an unusual setup as most single phase motors only have two windings with a capacitor shifting the phase for the second winding.

Cheers!

Marvo · Jul 1, 2021

Can you give more info about the motor? Is there a wiring schematic under the electrical cover? Can you post a photo of the info plate on the motor?

polaroid · Jul 2, 2021

I had a good look around it and the only other bit of info is the plate on the actual table (forgot to upload this initally). The motor plate must be concealed and would involve taking most of the underside apart. I can do it if needed but it's 100 miles away at the moment.

westward10 · Jul 2, 2021

How many functions did the control switch serve because the four core flex indicates more than one.

polaroid · Jul 2, 2021

Just a simple NVR on/off switch. This is what has confused me too. Picture below is from the same model on the internet.

Mike Johnson · Jul 2, 2021

JW video :

polaroid · Jul 2, 2021

Mike Johnson said:
JW video :

Thanks but all that is contained in the NVR switch, the problem I have is downstream of the switch.

marconi · Jul 3, 2021

The motor wiring looks like a star Y connected Steinmetz connection to run a 3 phase motor from a single phase supply. Is the capacitor about 140uF? Ie 70uF for each kW of rated motor power. The motor power is 2kW.

JS-Technik GmbH - https://www.js-technik.de/en/faq/detail/groupid/4/id/75

I would carefully label and record the ends of the wires in the terminal block and using a
multimeter set to low Ohms confirm the windings are connected star or delta and how the capacitor and power leads are connected to the motor coils. Note well that even if two wires to a coil are the same colour they must be connected back without introducing a swap over.

If you draw this out and post it folk will check it for you.

polaroid · Jul 3, 2021

Thanks Marconi. It's a 20uf capacitor.

I'll get the wiring diagram sorted next weekend when I visit him.

westward10 · Jul 3, 2021

Need to see the rating plate of the motor.

brianmoooore · Jul 3, 2021

marconi said:
The motor wiring looks like a star Y connected Steinmetz connection to run a 3 phase motor from a single phase supply. Is the capacitor about 140uF? Ie 70uF for each kW of rated motor power. The motor power is 2kW.

That was my first impression, but why the connection to the star point?

marconi · Jul 4, 2021

The motor used is I reckon a typical star wired one, wound with coils to operate from a standard three wire 400V line to line supply - so 230V across each coil in star configuration. To achieve the same winding voltage from a single phase 230V supply the star point is connected to neutral and two of the three coils to the 230V line. Steinmetz capacitor connection creates a phase shifted line supply for the third winding. A 230V line and N connection across two coils would reduce the winding voltage to 115V reducing motor power considerably.

polaroid · Jul 4, 2021

westward10 said:
Need to see the rating plate of the motor.

I'll make sure I get that too ?

polaroid · Jul 11, 2021

OK... Below is the motor plate and a wiring diagram. All connections were broken down and measurements made accross the windings with a MFT. I double checked it all as the resistances were not what I was expecting - values come out the same the second time around. The 3 windings resistances were 0.14, 2.1 and 6.7 ohms. The 3 core cable is the feed up to the switch. I'm guessing the difference in the winding resistances are not good.

Many thanks for the help.

marconi · Jul 11, 2021

The motor is single phase so what I mentioned about Steinmetz does not apply. I do not have time to think on what you have reported - big football game tonight - but I want to say that I would not be surprised if that motor has overheated and suffered internal thermal damage since the exterior cooling fins have been filled with sawdust and chippings which will act as superb thermal insulation blanket and hamper cooling by this surface construct.