Power Distribution Panels
Insulated Bus Ducts 400-6300A | UniRegal
Dense insulated busway, 3-phase 3/4/5-wire, 50-60 Hz, up to 400 V, rated 400-6300 A. Compact trunking from transformer to switchgear.
Specifications
- System
- 3-phase 3/4/5-wire, 50-60 Hz, up to 400 V (rated insulation 660/1000 V AC)
- Rated current
- 400 / 630 / 800 / 1000 / 1250 / 1600 / 2000 / 2500 / 3150 / 6300 A
- Conductor
- Copper Cu+Ag 99.95% min (sandwich-insulated)
- Housing
- Aluminium alloy 6063-T5
- Protection
- IP54 or IP65
- Standard sections
- 1.6 / 3 / 6 m; custom 0.5-6 m
- Functional units
- Straight, feeder with plug openings, plug-in boxes, elbows, T-taps, expansion, end feeders
- Standards
- IEC 60439-1/-2, GB 7251.1/.2 design basis
Insulated Bus Ducts for High-Current Distribution
Dense insulated busway carries high currents in far less space than cable: three-, four-, and five-wire systems at 50-60 Hz, up to 400 V, rated from 400 A to 6300 A. Copper conductors are sandwiched in insulation inside an aluminium housing, which is why the same current that needs a thick cable bundle runs through one slim trunk - and why it is the standard answer for transformer-to-switchgear links and vertical risers in buildings and plants.
Install directly from transformer to low-voltage switchgear, or use as distribution trunking with tap-off and connection boxes along its length.
Quick Answer: Bus Duct or Cable?
Choose bus duct when the run is long or the current is high - roughly 630 A and above - because cable becomes bulky, expensive and hard to terminate at those ratings; when the route changes direction often or runs through tight shafts, bus duct with factory elbows installs faster than pulling cable; and when you expect future tap-offs, plug-in openings along the duct let new loads connect without new switchgear. Choose cable for short, low-current, frequently rearranged runs. Many projects mix both: cable in the panel wiring, bus duct for the heavy vertical and horizontal feeders.
How Dense Insulated Busway Is Built
High-conductivity copper bars (Cu+Ag 99.95% minimum) are individually insulated and packed closely together - the 'dense' construction that shrinks cross-section and inductance - then enclosed in an extruded aluminium alloy (6063-T5) housing that provides mechanical strength and continuous shielding. Sections arrive as standard 1.6 m, 3 m or 6 m lengths (custom from 0.5 m to 6 m on request) and join with factory connection kits on site.
Functional Units for Any Route
A complete run is assembled from straight sections, straight feeder sections with plug openings, plug-in (tap-off) boxes, connection sections, expansion units, horizontal and vertical elbows, Z- and combined bends, T-taps and end feeders. That vocabulary covers a transformer hall down a wall, across a ceiling, up a riser shaft and into a switchgear room - or across a factory bay with drops to machines.
Tap-Offs Where You Need Them
Feeder sections can be supplied with plug openings at planned intervals, and plug-in boxes (with the protection you specify) clip onto them to feed a machine, a floor or a future load. Plan tap positions on the route layout before ordering so openings land where loads will sit; a later tap can still be added at a prepared opening or by inserting a short feeder section.
How to Specify a Bus Duct Run
Specify these five items and the layout can be engineered without guesswork:
1. System data: nominal voltage, frequency, and whether the run is 3, 4 or 5 wire (live, neutral, PE). The duct is rated to 400 V systems with 660/1000 V insulation class.
2. Current per section: continuous design current, and the rating of any future extension. Ratings run 400-6300 A; over-sizing by one step now costs little against re-running a duct later.
3. Route drawing: start and end points, heights, bends, wall/floor penetrations and where tap-offs are needed. Factory-made elbows and T-taps avoid on-site fabrication.
4. Environment: indoor clean, indoor dusty, outdoor or coastal. The aluminium housing is available in IP54 and IP65; say which your location demands and whether the run is exposed to sun, rain or washdown.
5. Tap-off schedule: each plug-in box's rating, protection and cable size, so the boxes arrive fitted and ready to terminate.
Key Details to Check Before Buying Busway
Conductor and Housing
Check the conductor grade (copper Cu+Ag 99.95% minimum) and the housing material - extruded aluminium alloy gives a strong, corrosion-resistant shell. Ask for the resistance and impedance values at your rating; they determine voltage drop over long runs and heat rejected into the room.
Protection Rating and Joints
IP54 keeps dust and splashing water out of indoor and sheltered runs; IP65 adds jet-water protection for outdoor and washdown areas. Joint design matters as much as the housing: ask how sections connect, how joints are torqued and sealed, and whether expansion units are included for long straight runs where thermal movement must be absorbed.
Fire and Arc Safety
Insulation between conductors must be rated for continuous service at full load and must not propagate flame. Ask for the insulation material and its temperature class, and confirm that tap-off boxes interlock or isolate correctly before opening - safety questions that belong in every specification.
Quality, Testing and Factory Evidence
Busway quality lives or dies at the joints, which is where factory inspection focuses. The plant runs an ISO 9001-certified quality management system with three inspection gates: incoming checks on copper conductor, insulation and housing stock; in-process inspection during section assembly; and outgoing testing of finished sections before packing.
The electrical test line includes a 100 kV-class AC/DC withstand test set for dielectric routine tests, insulation-resistance testers, and a loop (contact) resistance tester used to verify joint resistance on completed sections - the same parameter you should ask every supplier to evidence. DC resistance checks cover the conductor runs, and routine inspection records are available on request with your order.
Where Bus Ducts Are Used
Typical runs: transformer room to LV switchgear - often the first place busway replaces a wall of cable - then vertical risers in high-rise commercial and residential buildings, plant distribution along factory bays, data-centre halls, water and wastewater facilities, and hospital or airport critical-power feeders where one clean trunk beats dozens of parallel cables. In a switchroom project the duct usually starts at the low-voltage switchgear we also supply - ask for both in one RFQ so the interface is designed once.
Frequently Asked Questions
1. At what current does bus duct become cheaper than cable?
There is no universal number - it depends on route length, number of parallel cables and installation labour - but above roughly 630 A per circuit, and on any long or vertical run, bus duct usually wins on space, terminations and installed cost. Below that, cable is normally simpler.
2. Can tap-off boxes be added after installation?
Yes, at prepared plug openings - which is why it pays to specify feeder sections with openings at likely load points. For a location with no opening, a short feeder section with openings can be spliced into the run. Adding a new tap still requires an outage at that section, so plan openings generously.
3. What is the difference between IP54 and IP65 bus duct?
IP54 protects against dust and splashing water - sufficient for most indoor electrical rooms and sheltered plant areas. IP65 also resists low-pressure water jets, which is needed outdoors, in washdown areas, tunnels and coastal sites. If in doubt, specify IP65 for exposed routes; the housing cost difference is small relative to re-running a duct.
4. How is the duct connected to the transformer and the switchgear?
End feeders and connection sections terminate directly on transformer low-voltage bushings and switchgear busbars or cable compartments. Send the terminal arrangement (bar spacing, height, phase order) with your enquiry and we will match the interface - if we are supplying the switchgear too, it is designed together.
5. Can aluminium housing be used outdoors in coastal areas?
The aluminium alloy housing is corrosion-resistant and is the standard construction for IP65 outdoor runs. For aggressive coastal or industrial atmospheres, confirm the environment with us and we will recommend the right joint sealing and any extra protection for hardware.
6. What documents do I need to send for a bus duct quotation?
A single-line diagram or feeder schedule with current ratings, and a route sketch with start/end points, heights and bend locations. We will return a section-by-section BOM (straights, elbows, tap boxes, end feeders), a connection diagram and a price - most inquiries receive a response within 24 hours.
7. What routine tests do finished bus duct sections pass?
Finished sections are outgoing-tested under the factory's ISO 9001 system, including insulation resistance and power-frequency withstand routine tests, with joint (loop) resistance verified on completed sections. Ask for the routine test record with your quotation, and tell us if your project requires witness testing or third-party inspection.
Request a Bus Duct Quotation
Send your single-line diagram and route sketch for busway sizing - our engineers will confirm the current rating, section list and IP class before you commit. Use the contact form, or mention your WhatsApp number in the message - most inquiries receive a response within 24 hours.