Peter Simpson 1 | 26/07/2019 17:53:26 |
![]() 206 forum posts 9 photos | Could anybody out there give me some advice on an electrical problem I have in my workshop. I have a Meddings HS4 Donkey saw that has developed a fault. The saw runs off an inverter as its a dual voltage 3 Phase motor. Yesterday whilst sawing a piece of bar stock it tripped the workshop RCD, I have disconnected the three outgoing load wires from the inverter to the motor. When the saw is switched on the inverter runs to 50 HZ on the display all ok. When the motor is reconnected to the inverter the RCD trips as soon as the saw is started. I have checked the three motor connections to earth with my multi meter there are no shorts to earth in these. Not sure what to check next. The motor is a Newman B56D/ FB214 cannot find any info about this frame size on the net. |
Emgee | 26/07/2019 17:57:48 |
2610 forum posts 312 photos | Peter, you need to check for earth faults on the motor and associated cables with an insulation resistance tester at 500volts, Megger or similar. Emgee Edited By Emgee on 26/07/2019 18:14:29 |
Peter Simpson 1 | 26/07/2019 18:14:58 |
![]() 206 forum posts 9 photos | As I do not have a megger so it looks like I'm stuffed. If there was an insulation fault it would probably cost more than the saw is worth. As the motor is flanged to the body of the saw I cannot see the possibilities of changing the motor for a single phase motor. |
Martin Cargill | 26/07/2019 18:20:12 |
203 forum posts | I would think that the fault probably lies with the inverter. Is there anything else connected to the circuit that feeds it? The RCD will trip at 30ma but some of the 30ma could be coming from something else. The inverter (if its a modern one) should give a fault code and switch off, if it detects something being wrong with the motor Martin |
Peter Simpson 1 | 26/07/2019 18:41:35 |
![]() 206 forum posts 9 photos | Hi Martin The inverter is a Jaguar Cub the fault code on tripping is LU. The RCD is being tripped by the saw. I Will do some investigating into the fault code. I think it's an under voltage fault. Thanks Peter. |
Robert Atkinson 2 | 26/07/2019 18:46:08 |
![]() 1891 forum posts 37 photos | Hi Peter, Were are you located? Maybe some one near you can help. Robert G8RPI. |
Peter Simpson 1 | 26/07/2019 18:59:38 |
![]() 206 forum posts 9 photos | This is not the first time this has happened but all has been well for ages, could it be the motor / inverter pairing. The motor is a 1/2 HP the inveter output is 0.4kWatt is the inverter on it's limit. |
Martin Cargill | 26/07/2019 19:04:20 |
203 forum posts | LU is probably (from memory) undervoltage, it would show this if the power supply to it has tripped i.e. the RCD has shut off the supply.
Martin |
Emgee | 26/07/2019 19:05:42 |
2610 forum posts 312 photos | Just within the VFD max rating. Emgee |
Peter Simpson 1 | 27/07/2019 12:34:51 |
![]() 206 forum posts 9 photos | This morning I wired up a spare motor to the inverter . The motor ran OK, sad to say the spare motor is not suitable for the saw. I have stripped down the original "Newman" motor, other than a bit of dirt on the stator winding every thing looks ok. This afternoon I will give the internals a clean and the rebuild it. Fingers crossed that it works. |
Les Jones 1 | 27/07/2019 14:01:37 |
2292 forum posts 159 photos | Don't you have any friends with a megger that could check the insulation between the windings and case for you ? Les. |
Peter Simpson 1 | 27/07/2019 19:00:21 |
![]() 206 forum posts 9 photos | As stated earlier, this afternoon I stripped the motor down, cleaned the internals with a degreaser, blew it dry with the air compressor then rebuilt it, Rewired it to the inveter on the bench. All went well. Now to refit all the bits back onto the saw.....Fingers Crossed. |
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