How to choose copper busbar in high-voltage and low-voltage switchboards?

Copper row, also known as copper bus bar or copper busbar, is a long conductor made of copper with a rectangular or chamfered (rounded) rectangular cross-section (now generally used rounded copper row to avoid tip discharge), which plays a role in conveying current and connecting electrical equipment in a circuit.

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So, how to choose the copper busbar in high and low-voltage switchboards? How to calculate the load capacity and bending of copper busbar? More details as following,

Copper busbars are widely used in electrical equipment, especially in complete sets of power distribution devices; generally, copper busbars are used in U, V, W phase busbars and PE busbars in power distribution cabinets; 

Copper busbars are generally marked with phase color letter signs or painted with phase color, U phase copper rows are painted with "yellow" color, V phase copper rows are painted with "green" color, 

W phase copper coated with "red" color, PE busbar copper coated with "yellow and green" two-color answer.

Today we will learn the calculation of copper busbars!

1. The copper busbars of the load capacity calculation

First of all, we should understand that the installation of copper in the electric switchboards is divided into two forms, flat and vertical, vertical load capacity is slightly greater than the flat, 

so the main bus bar of the distribution cabinet is mostly vertical form. There are also copper busbars, copper wire load capacity will also change with the ambient temperature, 

where we use the most ambient temperature of 35 degrees Celsius. Under different ambient temperatures, 

the load capacity derived from the table needs to be multiplied by the correction factor for different ambient temperatures, 

the load capacity under different ambient temperatures, the higher the temperature, the lower the load capacity.

Based on experience, the summary is as follows.

Single copper busbar load capacity = width (mm) X thickness factor.

Double busbar load capacity = width (mm) * thickness factor x 1.5 (experience factor).

Copper and aluminum busbars can also be a square numbers, usually copper by 5-8A / square, aluminum by 3-5A / square.

Commonly used is a copper busbar of the load capacity calculation method.

40 ℃ when the copper row load flow = row width x thickness coefficient (thickness + 8).

Row width (mm); thickness coefficient is: 20 when the female row is 12 thick; 18 when it is 10 thick; in order: [12-20, 10-18, 8-16, 6-14, 5-13, 4-12].

Double-layer copper row [40℃] = (1.56-1.58) x single-layer copper row [40℃] (according to the size of the cross section).

3-layer copper row [40°C] = 2xsingle-layer copper row.

4 layers of copper row [40 ℃] = single copper row [40 ℃] x 2.45 (not recommended for this type of choice, it is best to use a shaped bus bar instead).

For example, to find TMY100x10 load capacity as follows

Single-layer: 100x188=(A) [check the manual for A].

Double layer: 2 (TMY100x10) the load capacity is: x 1.58 = (A); [check the manual for A].

Three layers: 3(TMY100x10): x2=(A) [check the manual for A].

All the above calculations are accurate to be quite close to the manual data

2, The calculation method of copper bending

AOKEYER Product Page

(1) flat bending (right-angle bending) outside the algorithm

The above figure has the following material lengths

Total length = a + (material thickness) + b + (material thickness) + c + d - coefficient x number of right angle bend

Note: Add material length all according to the additional

Coefficients are basically as follows.

(2) flat bend (right angle bend) within the algorithm

(3) Example

When the material thickness is 3mm, the total length= L+0.3+H+0.3

When the material thickness is 10mm, the total length= L+1.5+H+1.5

Note: Each corner is added twice

3, The choice of copper busbars in the high-voltage switchboards

High-voltage switchboards copper busbars cross-section selection needs to meet two requirements.

(1) to meet the rated current

(2) to meet the short-time withstand current

The first can be calculated through the load capacity, then the second need to write down the formula in GB [Appendix D]: S = I/a√(t/△θ) where: I - rated short-term withstand current; a - material coefficient, copper 13, aluminum 8.5; t - rated short-circuit duration; △θ - temperature rise (K). For bare conductor generally take 180K, for 4S duration take 215K.

Then.

25KA/4S system copper busbar minimum cross-sectional area S = (25/13)*√4/215 = 260 mm2.

31.5KA/4S system copper busbar minimum cross-sectional area S=(31.5/13)*√4/215=330 mm2.

40KA/4S system copper busbar minimum cross-sectional area S=(40/13)*√4/215=420 mm2.

63KA/4S system copper busbar minimum cross-sectional area S=(63/13)*√4/215=660 mm2.

80KA/4S system copper busbar minimum cross-sectional area S=(80/13)*√4/215=840 mm2.

The above two conditions accounting for the copper row cross-section needs to be selected as the maximum.

For example, the current parameters given by the design institute in a circuit are: rated current 630A, short-time withstand current 31.5KA, 

then the rated current 630A should use TMY-40 x 6, the short-time withstand current 31.5KA should use 

TMY-60 x 6 (31.5KA/4S copper busbar minimum cross-sectional area of 330 mm2 through the above table), 

TMY-60 x 6 cross-sectional area of 360 mm2. 60 x 6 cross section of 360 mm2 is greater than the minimum cross-sectional area of 330 mm2 in the above table.

According to the maximum value of the two conditions, the busbar with rated current of 630A and short-time withstand current of 31.5KA should be selected as TMY-60 x 6.

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Hello, I am wondering how to size my system amps wise, so I know how big to make my negative and positive bus bars? I know on https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html he uses a 250 amp bus bar, but that doesn't seem like enough is I am using a -watt inverter and 300 amps of battery. Granted I don't think it will ever actually run at watts fully. More like watts max. Thanks!

The generalized answer is you size busbars in roughly the same way you size wire, figure out the maximum current (amps) that will be flowing through that circuit, select a fuse that is larger than that number (1.25x or greater is the rule of thumb) than size your wire and busbars larger than the fuse.

As an aside, your battery does not have amps, amps are not something that can be stored or had. It is a unit of flow. Batteries are measured in amp-hours, which are a different type of unit, in the context of a battery it measures capacity or stored energy. Separating these two terms and concepts in your head, will help clarify a lot when it comes to properly sizing components.

As it relates to busbars and wire and most other components of your system, how much energy is stored by your batteries (amp-hours) is irrelevant, what matters is how much current will flow through each component of the circuit.

If you have a simple system, where all loads are AC (inverter) loads you can get a rough estimate of max current by calculating:

[Inverter Watts] / [Inverter Efficiency] / [Inverter Low Voltage Disconnect]
For example:
W / 0.85 inverter efficiency / 12v = 294A
294A x 1.25 = 367A or larger fuse

You can tailor those numbers to your situation, but that will give you a rough ballpark of maximum continuous current.

If you also have DC loads, they should be accounted for as well.

This observation you made is EXACTLY on point and pushed me into buying one of two options. One, was to buy the 600 amp versions from Blue Seas Systems, or two, buy the Victron Lynx Distributer with amp rating. The price was about $200 vs $150 and I decided to go the Victron system instead. I think all the sum of the parts add incremental additions to the efficiency of a system that is NOT cheap to begin with. I see a ton of people use undersized EVERYTHING. Crap, you only want to do it ONCE...so do it right.

How do you feel about the lynx distributor? do you like it? was it easy to use? I know you need to use mega fuses with it, and I've already bought a bunch of anl fuses for my system, do you think at that point I should just go with the blue sea bus bar since it's rated at 600- amps?

The generalized answer is you size busbars in roughly the same way you size wire, figure out the maximum current (amps) that will be flowing through that circuit, select a fuse that is larger than that number (1.25x or greater is the rule of thumb) than size your wire and busbars larger than the fuse.

As an aside, your battery does not have amps, amps are not something that can be stored or had. It is a unit of flow. Batteries are measured in amp-hours, which are a different type of unit, in the context of a battery it measures capacity or stored energy. Separating these two terms and concepts in your head, will help clarify a lot when it comes to properly sizing components.

As it relates to busbars and wire and most other components of your system, how much energy is stored by your batteries (amp-hours) is irrelevant, what matters is how much current will flow through each component of the circuit.

If you have a simple system, where all loads are AC (inverter) loads you can get a rough estimate of max current by calculating:

[Inverter Watts] / [Inverter Efficiency] / [Inverter Low Voltage Disconnect]
For example:
W / 0.85 inverter efficiency / 12v = 294A
294A x 1.25 = 367A or larger fuse

You can tailor those numbers to your situation, but that will give you a rough ballpark of maximum continuous current.

If you also have DC loads, they should be accounted for as well.

So basically add all the fuses I've got for my things? Since they are already sized to the systems?

How do you feel about the lynx distributor? do you like it? was it easy to use? I know you need to use mega fuses with it, and I've already bought a bunch of anl fuses for my system, do you think at that point I should just go with the blue sea bus bar since it's rated at 600- amps?

I had a damn limited amount of room to deal with! I liked the Victron Distributer because you could stack the in and output cables to one side. Or in my case, in on the left (if facing) and down for the outs. But don't forget, the best part was the ground bar (also a) was the only input to the smart shunt. Here is a pic. (Don't forget hard to see, but there are two levels, the hot side is actually inches above the ground terminals...I used 4/0 and it fits just fine.

Now, you'll need to get some additional screws and bolts, but the entire system is very well made and I would use it again.

positive from batteries, 400 amp fuse, to bar to shutoff ALL POWER
after shutoff/on, after bar on, cable travels under to shutoff/on for inverter only
after shutoff/on, all power to Victron busbar
ground from main battery post to smart shunt, bar to GROUND shutoff that feeds busbar

Attachments

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So basically add all the fuses I've got for my things? Since they are already sized to the systems?

I'm not sure, since I'm not sure exactly what you have purchased / are using.
It seems like from your original post you were worried about the busbar being undersized, if this is the case, using fuses sized appropriately for your loads would not remedy the situation as the busbar would still be undersized.

The basic order of things

Determine the max current of your circuits >> Size fuses for each circuit larger than the max current on that circuit >> Size the conductors (this includes wire, busbars, and any other current carrying component) larger than the fuses.

It sounds like (i've no way of knowing for sure) you have selected appropriately sized fuses, but are worried about the busbar being insufficient. If I were in your shoes I would just go a size or two up for peace of mind. Here is a semi-reasonably priced 600A busbar for $75

What size wire are you using with your inverter?