Harig 618 surface grinder wiring up 3 phase quick question

Hey guys, I got an RPC and just wanted to verify where to hook up the high leg of the 3 phase coming in to the machine? 2 lines are ~120v and one is higher, so not sure if I should put that on L1, L2, or L3? Anyone know? I've also included pics of the schematics on a drawing that came w/ the machine.


Here's the control panel of the sg




wiring schematics, not sure if this even helps

Put the high leg through the disconnect to 3FU (first schematic diagram), so that it's not used to feed the transformer T1.

I marked it in red here:

MichaelP said:

Put the high leg through the disconnect to 3FU (first schematic diagram), so that it's not used to feed the transformer T1.

I marked it in red here:

Click to expand...

that's exactly what I did after studying it... glad i made the right decision, thank you for confirming that!!

It wouldn't manner which line is the high leg. Any two will measure at 230V-240V respectively. As long as the taps on the transformer are set for 230-240V, you should be just fine. The output should be around 115-120v, with one leg grounded to the box ground, AND that leg serves as the neutral conductor for the control circuit as shown in your schematic. Ken

I have to point out the rather fried red wire to the LHS of the switch in pics 1 and 2 looks like the tape is hiding somthing too.

4GSR said:

It wouldn't manner which line is the high leg. Any two will measure at 230V-240V respectively. As long as the taps on the transformer are set for 230-240V, you should be just fine. The output should be around 115-120v, with one leg grounded to the box ground, AND that leg serves as the neutral conductor for the control circuit as shown in your schematic. Ken

Click to expand...

2 of the input lines coming from the RPC are measuring around 110v and the third is the 230 line... North America phase converters said that the high leg just needs to NOT go to the controls on the machine but must go to the motors. Seems to be running find but I haven't ground anything yet. any suggestions on wiring though that I should change?

Tray said:

I have to point out the rather fried red wire to the LHS of the switch in pics 1 and 2 looks like the tape is hiding somthing too.

Click to expand...

ohhh WOW good eye!! I had not even seen that, thank you! I did have 1 blown fuse (6-FU in third schematic pic, top left), maybe this had something to do with it? I wonder what the cause was.

razoredgeknives said:

2 of the input lines coming from the RPC are measuring around 110v and the third is the 230 line... North America phase converters said that the high leg just needs to NOT go to the controls on the machine but must go to the motors.

Click to expand...

Ken is correct for your particular schematics. In your case, there is no dramatic difference where you connect the hot leg because the transformer's primary is designed for 240V. Still...

I'm neither an electrician nor an EE, so please take my reasoning with a grain of salt. My understanding is that the recommendation not to connect the high (manufactured) leg to control circuits stems from the fact that some control circuits are designed for 120v and may derive it between the neutral and one of the RPC outputs. As you were able to see, only two legs have 120V when measured to the ground. The high (generated) leg measures much higher to the ground. So if you connect much higher voltage to the circuit designed for 120V, the result will be...well...

Also, in non-balanced RPCs, we often see that the voltage between the high leg and the other two is about 20% higher than the voltage between the two remaining legs. So even if your transformer's primary is 240V (as in your case) and will tolerate this higher voltage, its secondary coil feeding the control circuit will produce proportionally higher voltage too. Besides, AFAIU, the output from the non-manufactured legs is significantly "cleaner" because those are the direct continuation of the utility supply feeding your RPC.

Now, I always prefer uniform approach to wiring. For example, when I wire 240v single or 3-ph outlets, I always connect the same hot line to the same contact in every single outlet. Color of the wires are kept uniform whenever possible all the way from the source to the load, incl. room wiring and feeding cables. Although it's not necessary from the electric standpoint, it makes it easier to troubleshoot the circuits, and they are simply neat. OCD? Possibly...

Hence was my suggestion to avoid connecting the high leg to control circuit in your case. If you always [blindly] follow the rule, you will never damage/negatively affect your control circuits.