Sizing a Switch Disconnector for my Panel using 3 Phase & 1 Phase components.

[BradleyM]

Hello there

I have a panel i'm designing that contains inverter drives, Power supply and a UK Socket. I want to calculate the size of the Switch Disconnector needed using the current drawn from these components. I have 400VAC 3 phase & 1-Phase 230VAC. Here is a list of the components Current Consumption:
3 Phase Inverter/Motor 1 = 4A
3 Phase Inverter/Motor 2 = 8.5A
1 Phase Power Supply = 2.5A
1 Phase Uk Socket = 4A

I know the Disconnectors go up in different sizes but if I could have the total current I need. I'm basically not sure how to add 3 phase and 1 phase together. all calculations shown if possible please.
Much appreciated.

 

[Spoon]

Hi mate.
Are you talking about the isolator when you say 'Switch Disconnector'?
This will be sized for the power that is feeding the panel, not how much the panel draws.
What size breaker/fuse is being used for the feed to the panel?

 

[BradleyM]

Hi

Yes I am talking about the Isolator.
We always work by telling the customer what power we need so it can be anything. We know the voltage but then we work out the current everything is drawing. We can then use this to tell the customer what power need. The Isolator is the first thing the mains comes into the panel so the total current of the panel goes through this isolator.

Hope that makes sense

 

[Spoon]

So what power do you need for this panel?
From this you can get your isolator size.

or am I misreading your posts...

 

[BradleyM]

To work out the Isolator size I need to know the current my total components are pulling. That's why Isolators are sized in Amps to show how much load they can switch. The power doesn't matter. I don't know how much power I need because I don't know how much current I need. Work out current first then power, not the other way around.

 

[Bobster]

20 amp.

32 amp will probably be cheaper.

 

[BradleyM]

20 amp.

32 amp will probably be cheaper.

Can you show me how you worked it out please?

 

[Bobster]

I didn't, I just looked and gave you a worse case. Are the single loads going to be taken from the 3 phase supply?

Considering a 32amp isolator with interlocking door handle and shrouds is <£30 why spend more time on it?

 

[BradleyM]

I didn't, I just looked and gave you a worse case. Are the single loads going to be taken from the 3 phase supply?

Considering a 32amp isolator with interlocking door handle and shrouds is <£30 why spend more time on it?

Yes the single loads are going to be taken from the 3 phase supply. I'll probably take the power supply off the 1st phase and then the socket off the second phase.

I know that is less time but just wanted to know the exact calculations. Can you show me please?

 

[Bobster]

Just add all the currents up on L1 with anything else on L1, do the same with L2 and L3. See which ones the maximum.

Try to arrange them so they end up as near balanced as possible