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stoic

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So i bought a 3 phase woodworking machine. Problem is, my workshop only has a single phase plug :(

My main 3 phase DB is around 10m from my workshop so i have 3 questions:

  1. Type of cable used for a 3 phase extension to garage.
    • 4-core?
  2. How on earth does one wire it to the db :)
    • Do i connect each of the 3 live wires to L1, L2 and L3 and the fourth cable to ground?
  3. Can I somehow use the same cable for single phase?
    • Can i use one of the live wires and ground for single phase?

I want to add a small db in the workshop that will allow for single phase and three phase equipment. 

 

Edited by stoic
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12 minutes ago, SilverNodashi said:

You get a single phase to 3 phase transformer. Can't just wire those wires to the DB. the 3 phases in "3 phase" run 120 from each other to create a "loop" (in laymen's terms). 

Get something like this: http://www.cncdirect.co.za/htm/inverter.html

I have 3 phase coming to my plot, my entire plot is three phase, it is just the workshop that has no 3 phase power, so i want to extend the 3 phase power from my main db to my workshop, so there is no need for a VFD

Edited by stoic
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aha. I totally misread that, 

 

1. Yes, 4 core. "trailing cable" is easy to work with. The stuff Eskom use during installion is very hard and difficult to work with. 

2. Red to Red, Yellow to Yellow, Blue to Blue and Black to Black. It is important to to keep the phases in the same sequence. 

3. Yes. That's how your workshop it wired, from one of the live's + earth

4. You should have a separate DB for single phase and a separate one for 3 phase. Run one of the 3 live wires from the 3 phase DB to the single phase DB. Ideally you should first do a load test to see if the 3 phases are balanced. Easiest is with something like an Efergy meter and 3 CT clamps, one for each phase. Run it over a couple of days to see the load on each phase and get an idea of how balanced the circuits are. 

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2 minutes ago, SilverNodashi said:

aha. I totally misread that, 

 

1. Yes, 4 core. "trailing cable" is easy to work with. The stuff Eskom use during installion is very hard and difficult to work with. 

2. Red to Red, Yellow to Yellow, Blue to Blue and Black to Black. It is important to to keep the phases in the same sequence. 

3. Yes. That's how your workshop it wired, from one of the live's + earth

4. You should have a separate DB for single phase and a separate one for 3 phase. Run one of the 3 live wires from the 3 phase DB to the single phase DB. Ideally you should first do a load test to see if the 3 phases are balanced. Easiest is with something like an Efergy meter and 3 CT clamps, one for each phase. Run it over a couple of days to see the load on each phase and get an idea of how balanced the circuits are. 

Awesome thanks.... now to salvage some 4 core cable from somewhere :)

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2 hours ago, SilverNodashi said:

2. Red to Red, Yellow to Yellow, Blue to Blue and Black to Black. It is important to to keep the phases in the same sequence. 

It's called "Phase rotation" and if you swap them your electrical motors run in the opposite direction.

I would expect that if it is a TN-S or TN-C-S setup, you'll have 3 phase wires, a neutral, and a separate earth. That is 5 wires...

Edit: Though it might be allowed to carry the earth on the armouring of the cable... I'm not an electrician but I have seen it done.

Edited by plonkster
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  • 2 weeks later...
On 2019/03/14 at 11:29 AM, plonkster said:

It's called "Phase rotation" and if you swap them your electrical motors run in the opposite direction.

I would expect that if it is a TN-S or TN-C-S setup, you'll have 3 phase wires, a neutral, and a separate earth. That is 5 wires...

Edit: Though it might be allowed to carry the earth on the armouring of the cable... I'm not an electrician but I have seen it done.

will rather lay an earth :)

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