Power Cable Size

The cable protected by (i.e. downstream of) the 32A breaker (which I think is what you're asking about, if I read you correctly) should be sized for 32A.

The cable should be considered to bear the load of 32 A as the Main Circuit Breaker is of 32 A.

If you consider the cable of 10 A and in case of load increases higher that 10 A, then your cable will first get affected before Main Circuit Breaker trips the circuit.

Please explain your question more clearly.

So far you have one answer which will keep you safe (but may be more expensive than necessary), and one which may not stop your cable and surroundings bursting into flames (in the event of a fault) - depending on your wiring.

The appropriate cable rating depends critically on your layout.

Also, please explain "Power Cable PC-001". Is this an assembly supplied by a manufacturer? If so, please give the details.

http://ifile.it/7k2jr8l/PS%201.bmp

http://ifile.it/xjszt5b/power%20consump.bmp

The distance between PLC &UPS is 20 M, Will be routed Through Riased Floor.This is not a complex layout --Straight Run

PC-001 ( 02 Core Cable )is to be Procured by us, It will be connected between PLC (32A MCB) & UPS system

Gents , Thanks For all Your Info.

Regards

Jose

All cable upstream of the 6A fuses must be rated at 32A or greater.

I think you will find that the cost difference between a power cable able to provide 10A and one that will provide 32A is negligible for the length between the UPS and the panel.

If the length between these two is so great as to cause concern in price difference, then you have a larger issue to concern yourself with, wire resistance.

In any case, it is better to provide the breaker with the proper supply line even if the UPS is only a 1200W UPS. You never know what future technicians may do and you do not want your supply cable to be the weak link.

So there are 3 solid reasons to supply the panel with a 32A Power Cable.

1. Negligible Cost Differential

2. Lower wire resistance

3. Compatible power path.

Alternatively, you may wish to lower the 32A rating to 15A throughout:

1800W UPS

15A Power Cable

15A Circuit Breaker

This configuration relaxes some of the electrical requirements, keeps the power system compatible and still affords a 5A (50%) overhead above the load values.

Why don't you replace the 32 amp MCB with a 10 amp MCB. I also find it hard to belive that the PLC requires a supply of 10 amps.

Cheers

Joe

I suppose I should ask this question, how many outputs are there on this PLC?

The reason that I ask this is that the PLC outputs are probally rated at 3 amps at 230vac each. Are you, or has someone else summed up the total output current and decided on the 32 amp MCB?

I would in my design never over-rate a PLC outputs if the current of each output is only 3 amps, there is no way that I would be using a 32 amp MCB, if you have a fault you will blow the output module up before the MCB would tripp!

When ever i use a plc i design the system so that it would protect the output circuits of the plc, but having a 10 amp mcb or greater and if you have a fault, be prepaired to have replace the plc.

It is most inportant that when deciding the MCB size that it is rated for the maximum current of one of the outputs, not the sum of the outputs.

I have never seen a Plc that has an output ratting of 10 amp's let alone 32 amp's. take a serious look at the loading of the plc and get things right.

32 amp mcb connected to a plc gives me shivvers, there is no way i would go there, even 10 amps would worry me.

Cheers

Joe

I think he said it was a PLC panel.

Imagine if that panel was equipped with these: http://www.seltec.co.uk/products/details/8771.html

Then the Panel CB would need to protect it while still affording the full range of capability.

I thought he said with a load of 10 Amp.

Did you check out his links in #5?

Hi there,

Please download the following handbook. It will give you some insight on how to size your power cables correctly.

You can download the whole handbook or just pieces of it - but rather get the whole handbook.

Off the top of my head.

You have a 10A load at 20m distance and this cable would probably not be buried.

You have a 32A breaker. The breaker is here to protect the cable if you're not using fuses. You are only allowed a certain percentage volt drop - country specific. If you are not using fuses - your cable would have to have a bigger current carrying capacity than your breaker rating - otherwise the cable will become the fuse in the case of a fault.

If you are using the circuit breaker to protect the cable - the smallest cable size you could use would be 6mm which can carry 40A without being de-rated. This would be overkill as you could have probably used a 2.5mm cable and protected it with a 15A breaker.

Either way - have a look at the book and it will give you some insight as to how we size power cables.

Regards,

Craig

obviously 32 amp.......

"obviously 32 amp......." is not helpful to the OP or anyone else in the discussion unless you explain why. "Why" has already been explained. Your post is redundant.