Bus duct design support
For any of these problems
- I'm unsure about the capacity of the main Bus duct.
- I want to check the Bus duct's exclusive floor area.
- I want to compare the costs of cable wiring and Bus duct wiring.
1. Support Overview
KYODO KY-TEC provides design support for the introduction of Bus ducts. We confirm various conditions and support the creation of voltage drop calculations, installation diagrams, and cost comparisons with cable wiring that are tailored to the on-site design. We also create system diagrams based on voltage drop calculations.
2. Support for creating voltage drop calculation sheets
Voltage drop is a phenomenon in which the voltage on the receiving side is lower than the voltage on the transmitting side due to resistance in electrical circuits and the conversion of electrical energy into thermal energy. One way to reduce voltage drop is to increase the size of the main line.
The voltage drop calculation is calculated using the impedance method and simplified method based on the internal wiring regulations. This document calculates whether the Bus duct capacity selected from the load capacity falls within the voltage drop rate set by the internal wiring regulations. We support the creation of voltage drop calculations when considering Bus ducts.
Voltage drop rate specifications
Excerpt from internal wiring regulations
- As a general rule, voltage drop in low-voltage wiring should be kept to 2% or less of the standard voltage in both main and branch circuits.
However, if electricity is supplied by a transformer within the electricity usage location, the voltage drop in the mains may be limited to 3% or less.
Note 1: The section from the service line attachment point to the service entrance should also be included in the calculation of the main line. Note 2: When electricity is supplied from a transformer installed within the electricity usage location, the section from the secondary terminal of the transformer to the main distribution board is also included in the main line. - Regardless of the preceding paragraph, when the length of the electric wire from the secondary terminal of the supply transformer (or the point where the service line is attached if electricity is supplied from an electric utility company) to the load at the farthest end exceeds 60 m, the voltage drop can be calculated using the load current and can be calculated according to the table below.
Voltage drop when the length exceeds 60m
→ The table can be scrolled to the right
| From the supply transformer secondary terminal or drop wire attachment point | When electricity is supplied from a transformer installed within the electricity usage location | If you receive low-voltage electricity from your electric utility company |
|---|---|---|
| 120m or less than | Voltage drop (%) 5 or less | Voltage drop (%) 4 or less |
| 200m or less than | Voltage drop (%) 6 or less | Voltage drop (%) 5 or less |
| Over 200m | Voltage drop (%) 7 or less | Voltage drop (%) 6 or less |
Bus duct and cable trunk voltage drop formula (basic calculation formula for line voltage drop)
→ The table can be scrolled to the right
| Bus duct and cable trunk voltage drop type Impedance method e＝K(R･COSθ+X･SINθ)･I･L |
Branch cable voltage drop type Simple method e＝(K×L×I)/(1000×A) |
|---|---|
| e: Line voltage drop [V] K: Coefficient based on electrical system Between lines of single-phase two-wire and single-phase three-wire systems 2 Between lines of three-phase three-wire and three-phase four-wire systems √3 Between the neutral wires of single-phase three-wire and three-phase four-wire systems 3 R: AC resistance [Ω/m] X: Reactance (Ω/m) cosθ: Load power factor sinθ: √1-cos2θ I: Line current [A] L: Length (m) |
e: Voltage drop between earth and ground (V) I: Load current (A) L: Track length (m) A: Cross-sectional area of the wire used (mm2） K: Electric coefficient (single-phase neutral line: 17.8, three-phase line: 30.8) |
→ The table can be scrolled to the right
Reference Impedance Table (SS-T Type Shaft Star)
*Depending on the type of Bus duct, the characteristics differ, so the impedance and voltage drop will change.
Please refer to the impedance table in the relevant catalog.
■ Impedance and voltage drop
→ The table can be scrolled to the right
| frequency | Rated current (A) | Conductor dimensions (mm) | Impedance (10-6Ω/m) | Voltage drop (V/m) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Effective resistance R |
リアクタンス X |
Synthetic Impedance Z |
Power factor 100 | Power factor 95 | Power factor 90 | Power factor 80 | ||||
| Three-phase line-to-line | 50 Hz |
600 800 1000 1200 |
5×65×1 5×90×1 5×120×1 5×150×1 |
115.2 84.0 63.8 51.6 |
18.3 13.8 10.6 8.6 |
116.5 85.1 64.7 52.4 |
0.1197 0.1164 0.1105 0.1072 |
0.1197 0.1165 0.1107 0.1075 |
0.1160 0.1131 0.1075 0.1043 |
0.1072 0.1046 0.0994 0.0965 |
| 60 Hz |
600 800 1000 1200 |
5×65×1 5×90×1 5×120×1 5×150×1 |
115.8 84.5 64.4 52.4 |
21.9 16.5 12.7 10.4 |
117.8 86.1 65.6 53.5 |
0.1203 0.1171 0.1115 0.1089 |
0.1214 0.1184 0.1128 0.1102 |
0.1182 0.1153 0.1100 0.1074 |
0.1099 0.1074 0.1024 0.1001 |
|
| Single phase Line spacing |
50 Hz |
800 1000 1200 1500 |
5×65×1 5×90×1 5×120×1 5×150×1 |
115.2 84.0 63.8 51.6 |
18.3 13.8 10.6 8.6 |
116.5 85.1 64.7 52.4 |
0.0922 0.0840 0.0766 0.0774 |
0.0921 0.0841 0.0767 0.0776 |
0.0893 0.0816 0.0744 0.0753 |
0.0825 0.0755 0.0689 0.0697 |
| 60 Hz |
800 1000 1200 1500 |
5×65×1 5×90×1 5×120×1 5×150×1 |
115.8 84.5 64.4 52.4 |
21.9 16.5 12.7 10.4 |
117.8 86.1 65.6 53.5 |
0.0926 0.0845 0.0773 0.0786 |
0.0935 0.0854 0.0782 0.0795 |
0.0910 0.0832 0.0762 0.0775 |
0.0846 0.0775 0.0710 0.0722 |
|
Note 1: The values in the table are calculated by calculating the voltage drop using K x rated current x route length (per meter) x (Rcosθ + Xsinθ). (K: three-phase = √3, single-phase = 1).
Note 2: The values in the table are voltage drops between lines (three-phase) and between neutral lines (single-phase) when the rated current is flowing.
Note 3: For voltage drop other than the rated current, multiply the value in the table by the ratio (actual load current/rated current).
3.Bus duct fitting diagram support
We support the creation of drawings for the exclusive area required for Bus ducts, etc. We also support the creation of installation drawings for things like support intervals for multi-system installations and maintenance spaces for branch boxes, which are difficult to convey in catalogs.
Reference: Fitting diagram
SS-T type shaft star (5 lines)
Floor support section detailed reference diagram
4. Create a cost comparison table
The cost comparison table helps you calculate the difference in cost between cable wiring and Bus duct wiring. Bus ducts are often thought of as more expensive than cables, but when you calculate the total cost of materials and construction, there are many cases where Bus duct construction is cheaper. We provide design support tailored to the site.
Reference: Cost comparison table
SS-T type shaft star (4 systems)
Example of cost reduction rate calculation for CVT cable (18 systems)
For questions about this support,
If you have any questions,
Please feel free to contact us.
