110 V Motor Question

[Blackpool]

OK right, so the cable from the NVR seems to be 4-core. If we number the three white terminals in a row 1 - 3 we have:
1 - brown switched line from NVR > two blacks into motor
2 - grey switched neutral from NVR > white into motor
3 - black switched line back to NVR hold coil via thermal protector > thin blue into motor

So the first circuit that we should see is zero ohms between 1 & 3 to enable the NVR coil to operate.
Then, we should see the motor main winding between 1 & 2.
The auxiliary winding and switch we have to measure by breaking into the capacitor leads but if there's nothing happening then we begin with the main winding.

What are the resistances 1-2, 1-3?

Terminal screw heads were not reliable (no clean contact - dust, age corrosion etc) so to establish the correct reading I cleaned the crimped brass end fittings on each wire with wire wool and then reinserted into terminal block. Then touched the respective ends with thin gold plated probes.

1-2 = 0.3 Ohms (initially fluctuated between 0.3, 0.4 and 0.5 Ohms - settled quickly at 0.3)
1-3 = 0.0 Ohms

 

[Lucien Nunes]

Well then something should be happening.

• There is solid zero-ohm continuity from 1-3 through the thermal protector so the NVR coil circuit is complete and should hold on (does it?)
• There is continuity of a fraction of an ohm through at least the main winding from 1-2 so the motor should hum or try to do something, even if it doesn't start normally.

We need to either prove that there is no power reaching the main winding, or that it is indeed getting power and any failure to start is localised to the auxiliary winding, centrifugal switch and/or capacitors. Latch on the NVR or hold the start button in by hand and check for the presence of 230V between 1- brown and 2- grey. Beware the possibility of the motor starting unexpectedly if an intermittent connection is disturbed.

If there is no 230V there, something is still amiss with the NVR connections. In theory, safety issues aside, it should be possible to make the motor operate independently of the NVR by disconnecting the incoming brown/grey/black cable from the white terminal blocks and connecting the mains supply directly L to 1 and N to 2 in place of brown and grey.

Out of interest, what exactly is this machine?

 

[Blackpool]

Well then something should be happening.

• There is solid zero-ohm continuity from 1-3 through the thermal protector so the NVR coil circuit is complete and should hold on (does it?)
• There is continuity of a fraction of an ohm through at least the main winding from 1-2 so the motor should hum or try to do something, even if it doesn't start normally.

We need to either prove that there is no power reaching the main winding, or that it is indeed getting power and any failure to start is localised to the auxiliary winding, centrifugal switch and/or capacitors. Latch on the NVR or hold the start button in by hand and check for the presence of 230V between 1- brown and 2- grey. Beware the possibility of the motor starting unexpectedly if an intermittent connection is disturbed.

If there is no 230V there, something is still amiss with the NVR connections. In theory, safety issues aside, it should be possible to make the motor operate independently of the NVR by disconnecting the incoming brown/grey/black cable from the white terminal blocks and connecting the mains supply directly L to 1 and N to 2 in place of brown and grey.

Out of interest, what exactly is this machine?

Yes the NVR energises and holds. But no hum or any movement.

The plant is a plate compactor (wacker plate). Albeit it is 110V (for on site safety - UK law) not 230V - so uses an external transformer (plugged directly into main domestic circuit so no extension cord voltage drops). Distance from domestic supply is 1m to transformer (using 3.3kva transformer's own inbuilt cable) and then used plant's own 1m harness cable to NVR. Transformer is brand new and rated to handle plant continuously (and tested on other plant).

Will check the voltage between 1 and 2 and then try the by-pass you suggested and revert back to you.

Manufacturer said they would be surprised if it was the motor (they are reliable) and suggested either NVR switch or capacitors as their initial thoughts. Manufacturer also confirmed fan can be removed with a couple of pry bars to gain access to centrifugal switch.

 

[Blackpool]

Yes the NVR energises and holds. But no hum or any movement.

The plant is a plate compactor (wacker plate). Albeit it is 110V (for on site safety - UK law) not 230V - so uses an external transformer (plugged directly into main domestic circuit so no extension cord voltage drops). Distance from domestic supply is 1m to transformer (using 3.3kva transformer's own inbuilt cable) and then used plant's own 1m harness cable to NVR. Transformer is brand new and rated to handle plant continuously (and tested on other plant).

Will check the voltage between 1 and 2 and then try the by-pass you suggested and revert back to you.

Manufacturer said they would be surprised if it was the motor (they are reliable) and suggested either NVR switch or capacitors as their initial thoughts. Manufacturer also confirmed fan can be removed with a couple of pry bars to gain access to centrifugal switch.

No power is reaching the terminal block. Which is odd because the other day there was some voltage.

Results :

104V into NVR (at +ve and -ve terminals on input side)
104V out of NVR (at +ve and -ve terminals on output side)
But nothing reaches the terminal block.
No damage in NVR to terminal block harness.

My original thought was the cut in between the plug and NVR may have shorted or blown something in the NVR?

I ran the bypass (basically severing the plug to NVR harness where the cut was ... leaving the earth still running to NVR and wired +ve and -ve into the terminal block and the motor fires up.

Is the issue likely to be the NVR contactor?
Do I still need to check the auxiliary winding and centrifugul switch?

 

[Lucien Nunes]

104V out of NVR (at +ve and -ve terminals on output side)
But nothing reaches the terminal block.

Could there even be a break in the 4-core cable?

 

[Blackpool]

Could there even be a break in the 4-core cable?

That run of cable looks perfect. Its only just over 2 feet long and it securely clipped to the frame every 7 inches. So no real opportunity to break

I will test by checking the continuity of each wire from NVR output to terminal block.

I have a volt stick that glows when it detects power along a cable (and stops when there is a break) but it does not work on 110V

 

[Blackpool]

That run of cable looks perfect. Its only just over 2 feet long and it securely clipped to the frame every 7 inches. So no real opportunity to break

I will test by checking the continuity of each wire from NVR output to terminal block.

I have a volt stick that glows when it detects power along a cable (and stops when there is a break) but it does not work on 110V

I think you may have cracked the case Lucien !

Continuity across each pair of terminals on NVR when I press the button so NVR looks ok

BUT one wire (the grey one) has no continuity from NVR to white terminal block. The brown and black do. So even though the cable looks pristine there must be a break in the grey. The cable is fastened to the frame which is a fold down and fold up all in one u shaped handle and I suspect the frequent folding down (to gain access to grab handles for lifting .. it weighs 50kg ... you cannot lift by the handle there are special grabs) and then folding up to use the plant (or storage) must have weakened the grey wire and its broken.

Will replace the cable tomorrow and update you.

Thanks you ever so much for all your help Lucien. Much appreciated.

Next job is my 240V washing machine motor (which is not running or even offering) So I may well be back on here within the week after I have done some basic tests ...

 

[Lucien Nunes]

Result! So you had line continuity from the NVR to the motor feed and a return to hold the coil on, but no neutral reaching the motor itself. At least it's a much easier / cheaper repair than something deep inside the motor.

Hopefully the washing machine will yield to similar investigation presently...