Table saw motor wiring

[polaroid]

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:

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]

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]

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]

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

 

[polaroid]

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]

JW video :

 

[polaroid]

JW video :

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

 

[marconi]

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]

Thanks Marconi. It's a 20uf capacitor.

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

 

[westward10]

Need to see the rating plate of the motor.

 

[brianmoooore]

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]

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]

Need to see the rating plate of the motor.

I'll make sure I get that too ?

 

[polaroid]

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]

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.

 

[marconi]

I have submitted a query to FERM Genemuiden NV on how the wires should be connected.


FERM DIY - Power Tools - Power to create - https://ferm-diy.com/en/power-tools

 

[marconi]

Ferm replied but had no information amongst their records on the motor for this old table saw.

please draw out switch wiring and post some pictures too.

 

[polaroid]

Ferm replied but had no information amongst their records on the motor for this old table saw.

please draw out switch wiring and post some pictures too.

Thanks for your time Marconi.

Unfortunately I don't have the wiring of the old switch, this is the issue.

I have few pics of the old NVR switch mech which i forgot to post the other night. Just no clue how it was wired up.

I appreciate this is an old saw so it's not worth a lot however I'm learning a great deal from this and it has me very curious as it appears to be a very unusual setup.

 

[polaroid]

I have read some single phase motors have start/run windings with different resistances so that may account for the values i got. However, all the single phase motors i find reference to have two windings.

 

[marconi]

I need to find a reference to confirm but I reckon after studying your winding diagram, your mention of a nvr switch and the fact this is a table saw and therefore short duty operation Ie short periods In use and much longer off

1. The motor will be a permanent capacitor split phase induction motor perfect to give high starting torque for rapid acceleration up to high speed 3000rpm and good speed regulation;

2. One would want the supply to be only held on when the supply is available and at the correct voltage and frequency.

3. If the motor stalls or the speed drops below a certain rate the supply is disconnected;

4. If the motor fails to start to turn or does not run up and exceed a certain rate the motor supply cannot be held on.

5. The motor must turn at sufficient speed for the fan to cool it.

Requirements 2 to 5 can be met if the motor speed is sensed. I think but need to check that the lowest resistance winding is a coil which senses electromagnetically the rotational speed of the motor. the output of this coil is the energising supply for the hold on coil in the no volt release switch.

see attachment for how the wires should be connected at the motor. Blue and brown are 230V supply to start and run,windings. Between Black and blue is the generated voltage indicating satisfactory speed of rotation which is connected across nvr contactor coil.

I will research typical nvr switches as used in saw tables but that will be tomorrow morning now to confirm my line of thinking.