3 phase supply.

[funkguppy]

Hi.

Looking to pick someone's brain.

In a commercial (formerly industrial) building, i have been asked to run power to a 3 phase lathe. There is a 3 phase board in the vicinity but it's a bit old and has BS3036 fuses. Problem is the fuses are not interconnected, so if one fuse blows, the other two are still live, causing problems with safe isolation and the motor itself. If it was a modern board, i could have fitted a triple pole MCB.

Any ideas as to the best solution?

Thanks.

 

[johnboy6083]

in almost all switchfuses ive seen, there is not interconnection between phases. Does the lathe have a control panel? If it has, it may have a phase failure relay, which will cut the supply in the event of a loss of a phase. In my experience, a motor that loses a phase becomes very noisy, vibrates a lot, and then the other phases blow shortly after

 

[telectrix]

could you split the tails into a 3 phase MCB, then to the lathe via 3 phase isolator?

 

[funkguppy]

Thanks johnboy (fellow Rochestarian). It's a fairly basic half horsepower model, probably no complex circuits. I did read that losing a phase will cause the other phase windings to burn out quickly. I take it that some people do use three separate fuses to power three phase equipment. Didn't know about these safety cutout devices. Will read more on them.

 

[funkguppy]

Sounds like the best solution. Thought about that, but so much better when someone else confirms this. Cheers telectrix.

 

[johnboy6083]

im no expert on them either mate.

 

[Des 56]

As you know the big problem with a machine losing a phase is on restart, they can run on the 2 phases sometimes ,It doesn't get going,low back emf,high current,warmth, then death
If the dist board supply to that machine were 3 seperate fuses,then I would do, as has been suggested, and install a unit with a 3 phase mcb (or even 3 singles with a steel pin to interlock them ) better than chancing the dreaded burn out that could happen