[Newbie] 3 Phase Question

[Brendan M]

I had to do some research on 240/415 3 phase. Never used it or heard of it before. Was it only the transformer burned out? I may have misunderstood your original post. From what I see you needed the neutral at the lathe for the coolant transformer. One leg of the 415 to neutral will supply 240 volts to the transformer unless the transformer is dual voltage input then you can use two legs and change the input taps. A schematic of the control box would be helpful.

Hi Jim , found this schematic.
Could you have a look and see what you think.
I think I was correct with my way, I have no idea how the electrician wired it.
Thanks

What type of lathe, and is the work lamp a Lovolite? some lovolite transformers used two phases and stepped down to 24v (some were 50v I think), some used phase to neutral (240V) It may have burned because it was a phase to neutral model that has been wired across two phases (415V) Very unusual to have a 3 phase lathe with a 240v pump and light, without the wiring being totally seperate, can you post up some pics?
Phil

Thanks Phil
I have made a few mistakes, sorry. The transformer is 415v In 220v/24v out . The coolant pump is 415v single,The Light 24v Halogen no branding , DRO 220v. The lathe is a Hafco Metalmaster AL-356. I am going to lift the lathe out today and then I will take some pics. The transformer will be Tuesday , I guess I will put it in and try it.
Thanks
Brendan

 

[British Steel]

Hi Brendan,

looking at that schematic, the coolant pump is 415v 3-phase - it's M2 in the diagram, controlled via KM3 contactor (coil KM3 on the far right, suds switch SA1 above it) which applies all three phases.

M1 is the main 2-speed spindle motor fed by forward and reverse relays KM1 and KM2 and the two-speed switch SA2 - note SA2 also has an interlock contact set (SA2-1, on the right above KA coil) in the feed to KA (which in turn supplies 24vac power for KM1 and KM2 coils) to drop the forward and reverse contactors out during speed switching, this is important and shouldn't be monkeyed with!
Also not to be monkeyed with are the KM1 and KM2 contacts in the feed to their opposites (just above the rectangles representing KM1 and KM2 coils) - these interlock the two contactors so that if one is operated the other can't - preventing shorting the incoming 3-phase through KM1 and KM2 feeding the motor in forward and reverse both closing...

It doesn't need a neutral on 3-phase, as clearly shown on the diagram - only L1-L2-L3 and the PE Protective Earth are needed.

I suggest you strip what the (incompetent?) electrician did, and "wire to diagram" (the wires / terminals should all be numbered) *BEFORE* you fit the new transformer, he could have done *anything* in there if (big likelihood) he doesn't understand what he's trying to do! Then connect up by connecting the PE conductor to XB (a link from the low-voltage ground to the high-voltage ground) or the machine's main earth connection, and the generator's 3 phases to the incomer switch QS1. Or, get an electrician who DOES understanad machinery and *knows what he's doing* to wire it for you if it sounds too intimidating!

Just my ha'pennorth, hope it helps,
Dave H. (the other one)

 

[Brendan M]

Hi Dave,
I have just finished going over the lathe wiring, for the life of me I can not understand what the electrician was trying to do.
I have wired it to the diagram and then checked it against the diagram from the technical rep sent.
I maybe $400 out of pocket but the electrician left his new Fluke multimeter behind in his rush to leave.
I am overwhelmed by the help everyone has given.
Many thanks to you and to everyone.
I should have trusted myself .
Regards
Brendan

 

[jim18655]

I don't see what he could have done to burn out the transformer assuming he only connected the line wires to the incoming terminals. Only way would have been to connect one of the hot legs to ground which would have back fed the transformer. If he did that then I would expect a lot more damage - burned out lamps, DRO, and maybe coils. Also the main motor wouldn't have run right on single phase. I'm starting to think it may have been a coincidence that the transformer went.

 

[Brendan M]

Hi Jim,
I have not tested anything yet, I just went through the numbers on the diagram.
I cant tell what he did because when he came back he disconnected the transformer and other wiring.
If he had come back, I would have to agree with you. He will not return my calls and you don't walk away from expensive tools.
I don't think he is going to tell me what is what, everything else seems ok ( nothing else burnt ).
Transformer will be here tomorrow and maybe I will get the supplier to install.
Regards
Brendan

 

[Brendan M]

Hi Guys
Sorry been down with walking gear problems.
So to finish the story, no problem with the generator ( apologised to Electrician and even gave back his multimeter )
Transformer was replaced by the supplier. Lathe ran fine, tested for 2 hours Great. He put it all back together ,cover on.
Next day started lathe and in 2 minutes burning smell, supplier changed transformer again - same crap.
To say I was P***ed off didn't make it.
Anyway the end of the story, I got a crash course in electrics, went through every wire myself.
2 wires on the 24 volt contacts had bad insulation , no fault when the wires were un bundled . Put a cable tie on and poof.
Once again Thank You to all ,
Regards
Brendan