3 phase factory lighting

[bal]

Hi - first time post:

Hi,

I'm a technician in a factory and have been tasked with sorting the lights out. We have approximately 60 x 250 w single phase halogen lights which I would like to control via contactors. Without going into detail the following is my take on things:

I've got a basic design where I have 3 phase plus neutral coming into a control box, this would then be split into 6 single phase feeds - two from each leg of the 3 phase feed. Each single phase supply would feed one contactor which in turn would switch 10 lights (6 contactors - 60 lights). For load balancing each leg of the 3 phase supply would therefore feed the same number of lights (20 lights each).

Each radial light circuit would be protected by a B6MCB. The single phase feeds (one per contactor) would be protected by a B25MCB each.

Should I be looking at protecting the incoming 3 phase feed with a 3 pole plus neutral MCB or should a simply fit 3 individual fuses on the 3 lives??

I understand that if I use a 3 pole plus Neutral MCB if one phase is overloaded the whole breaker will trip. If I use 3 individual fuses and one blows wont the remaining phases be unbalanced??.

Any thoughts would be appreciated. I

Hope I haven't lost anyone lol!!

regards

 

[UNG]

I'm not quite clear on what you are protecting with the B6 mcb is it the contactor circuit or the actual lighting load as it is undersize for 10 x 250w fittings and 15 / 20A may be more appropriate to cope with inrush

Can you post a diagram of what you propose

 

[pmac10]

your 3 fuse idea is a good one and i wouldnt worry too much about imbalance, think of the impact 40 lights on L2 & L3 will have on your overall plant loading (ive worked in relatively small factories with multiple motors pulling 300A per phase). i also agree with above coment on the B6 breaker.

 

[nickblake]

I wouldnt use a tripple pole MCB use individual ,if you do get a fault the you only loose one circuit , the other thing is whats the emergency light situation factories / workshops ive worked in a dark places so may be an idea to put some twin beams in , halogens i take you mean the son / MH fittings ?? watch the mcb type dont put a B type in a board with C types and use 25 amp contatcors as the inrush will be quite high

 

[mechelec]

how about using 10A 3 pole pole mcb's each feeding one contactor this gives 10 * 230V = 2300 W per phase
divide this by 1.8 correction factor gives 1278 watts per phas divide this by 250w (perlamp) = 5 fitting per phase 15 per contactor. This means only 4 contactors for 60 fittings.

split the fittings into banks and you will only lose a quarter of all the fittings if an mcb trips

 

[nickblake]

correction factor is multipied so 2400 x 1.8 = 4320 / 230 single phase = 18.78 amps

 

[mechelec]

correction factor is multipied so 2400 x 1.8 = 4320 / 230 single phase = 18.78 amps

Thanks you are right

 

[bal]

I'm not quite clear on what you are protecting with the B6 mcb is it the contactor circuit or the actual lighting load as it is undersize for 10 x 250w fittings and 15 / 20A may be more appropriate to cope with inrush

Can you post a diagram of what you propose

Thanks for the info - I'll try to post up a diagram later. The B6's would be protecting the actual lighting load. As I would be using a 4 pole contactor I would be connecting max 3 lights to each B6 which would then be connected to one pole of the contactor. The B25's would protect each the contactor.

I'm at work on a Monday morning - so I'll try top post a diagram later.

Daigram posted - see lighting2.pdf

regards

 

[bal]

your 3 fuse idea is a good one and i wouldnt worry too much about imbalance, think of the impact 40 lights on L2 & L3 will have on your overall plant loading (ive worked in relatively small factories with multiple motors pulling 300A per phase). i also agree with above coment on the B6 breaker.

I've got no problem with imbalance as the configuration would make sure each switch trigers a balanced load across the 3phases.

As regards the B6 - this would be covering max 3 lights (see previous reply). Should I fuse the neutral also?? - see my diagram lighting2.pdf

 

[bal]

I wouldnt use a tripple pole MCB use individual ,if you do get a fault the you only loose one circuit , the other thing is whats the emergency light situation factories / workshops ive worked in a dark places so may be an idea to put some twin beams in , halogens i take you mean the son / MH fittings ?? watch the mcb type dont put a B type in a board with C types and use 25 amp contatcors as the inrush will be quite high

Exactly - your point about B's & C's taken. Emergency lights are one separate circuit - no problem. Yep Sonpaks. Yep I was looking at 4 pole 25amp contactors. Shouls I go C across the board or B?? - in your opinin.

regards

 

[bal]

how about using 10A 3 pole pole mcb's each feeding one contactor this gives 10 * 230V = 2300 W per phase
divide this by 1.8 correction factor gives 1278 watts per phas divide this by 250w (perlamp) = 5 fitting per phase 15 per contactor. This means only 4 contactors for 60 fittings.

split the fittings into banks and you will only lose a quarter of all the fittings if an mcb trips

Thats exactly what I was thinking but usings4 pole contactors. Excellent idea about the 3 pole MCB to cover but I was thinking 25amp.

Take a look at the diagram that I'm posting and let me know what you think. Should I have a 4 pole MCB for the 3 phase or 3 individual fuses??.



regards

 

[bal]

Lighting diagram attachedView attachment lighting.pdf

 

[nickblake]

Definatly type C with the inrush current of the son type fittings you could have a tripping problem ,if each of the fittings are 250 watts thats = 10 x 250 x 1.8 correction factor = 4500 so
divide that by 230 = 19.56 amps

may want to use 5 fittings per circuit

hope that helps

 

[nickblake]

looking at the diagram the main mcb may cause problems very close to the limits and if you do get a fault its probably going to trip the 25 amp MCB loosing all four circuits , best option i feel is mcb , contatcor, light and also any link wires between the main mcb and the sub mcb would have to be 6mm although only short runs , feel its adding extra cost and work

 

[bal]

looking at the diagram the main mcb may cause problems very close to the limits and if you do get a fault its probably going to trip the 25 amp MCB loosing all four circuits , best option i feel is mcb , contatcor, light and also any link wires between the main mcb and the sub mcb would have to be 6mm although only short runs , feel its adding extra cost and work

Nick,

I was looking at maybe a 50amp 3p + N to cover the 3 phase in feed so no phase overloads (see new diagram) - also isolates the whole control box from a single point, although if tripped it would turn all the lights off (we do have emergency lighting) - do you think I should instead use 50amp fuses instead so if tripped I would at least have some lighting on??. The B25's are covering the contactors which would be 25amp. Agreed on the 6mm wire between each phase of the input 3 phase and the B25 MCB. Cost is no problem - this layout gives us the ability to control via 24vDC, programmable relay, or simply to 24dc relays and switches located anywhere in the factory.

 

[nickblake]

Fuses sound a good idea to prevent loosing all the lights , what still concerns me is the amount of lights per mcb 10 thats alot of load as you can see from previouse message .on drawing its a B6 , i am correct is saying 250 watt each or am i mistaken and they are son / MH . I take it you mean a 50amp MCB dont get mixed up with isolator and MCB , MCB's dont like being used as switches , so you could always use a switch fuse say 63 amp switch fuse and derate the fuses accoring to your loadings then you can protect the circuit and isolate as well ,instead of using an MCB for isolation

 

[pmac10]

bal, cant see your diagram mate, but wouldnt bother fusing neutral as it provides a safe current return path for imbalanced loads. if the fault doesnt blow a fuse on the way in, its not likely to blow one on the way out having done work

 

[mogga]

on street lighting circuits we had problems when running anymore than 6 no400w son t fittings if one went faulty it would take out the mcb rather than the fuse in the fitting due to the additional fault time req for fuse against mcb


ie 400wx1.8 /230v = 3.14a per fitting 5 per curcuit =15.6a each fused @ 10A the mcb trips taking them all out as nick says

 

[bal]

Fuses sound a good idea to prevent loosing all the lights , what still concerns me is the amount of lights per mcb 10 thats alot of load as you can see from previouse message .on drawing its a B6 , i am correct is saying 250 watt each or am i mistaken and they are son / MH . I take it you mean a 50amp MCB dont get mixed up with isolator and MCB , MCB's dont like being used as switches , so you could always use a switch fuse say 63 amp switch fuse and derate the fuses accoring to your loadings then you can protect the circuit and isolate as well ,instead of using an MCB for isolation

Thanks for the pointers Nick - on further investigation the lights are mercury vapor 250w single phase.

I'm thinking of changing the MCB's from B to C rated and increasing the supply to the whole box (see reply to Mogga below- "you reckon I should up the whole supply?? ie 60amp feed, C30 MCB to 30A contactor to C10 MCB's to lights to cover any current surges".

Good idea about the switch fuses, I didnt know that MCB's dont like being used as isolators - can you recommend a manufacturer??

Thanks for all your input.

regards

 

[bal]

bal, cant see your diagram mate, but wouldnt bother fusing neutral as it provides a safe current return path for imbalanced loads. if the fault doesnt blow a fuse on the way in, its not likely to blow one on the way out having done work

As per Nickblakes suggestion - I'm going to install switch fuses, understand your suggestion about not having to fuse the neutral - thanks for the suggestion, I'll change my scheme.

regards