Description
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Mobile Temporary Power Unit
This temporary three phase distribution box is a mobile class of temporary power assembly designed for short-term power distribution on construction sites, machinery rental yards and outdoor engineering sites. Pre-integrated circuit overcurrent protection, equipped with IEC60309 industrial connectors. All design parameters address common on-site electrical risks during field deployment.
1. Mechanical Structure
- Enclosure: Integrally moulded high-impact modified PP plastic, black anti-slip contour design, dual integrated carrying handles for two-person transport. Bottom thickened base prevents overturning on uneven ground.
- Input connector: 1 × 63A 5P male industrial plug (3L+N+PE, red IEC60309)
- Output sockets: 4 × 32A 5P female IEC60309 sockets (3-phase 380~415V)
- Protection module layout: Two transparent hinged cover compartments externally mounted on enclosure.
- Upper compartment: 4-pole miniature circuit breakers for branch overload & short-circuit protection
- Lower compartment: Common L1/L2/L3/N/PE terminal block for internal bus connection inspection
- Socket structure: External wall-mounted sockets with sealed protective caps for idle outlets. All fasteners are stainless steel to resist site moisture corrosion.
- Engineering practical advantage: External transparent protection covers avoid opening the whole enclosure to inspect breaker status, reducing ingress of construction dust and water.
2. Electrical Working Principle
- Three-phase five-wire distribution system (L1/L2/L3 + Neutral + Protective Earth)
- 400V three-phase power enters the unit via the 63A 5-pin input connector to the main internal busbar.
- Main busbar feeds 4 independent three-phase output circuits. Each circuit is controlled by dedicated 4P MCB.
- All output sockets share unified PE earth busbar to ensure continuous earthing for connected loads.
- Terminal block provides accessible test points for field technicians to measure phase voltage, neutral voltage without dismantling internal wiring.
Solved field pain point: Independent branch MCB prevents single equipment fault cutting power to all connected machinery. Fault circuit isolation can be completed without powering down the whole distribution box.
3. Construction Materials
| Enclosure: | Modified polypropylene, impact resistant, anti-aging, resistant to splashed water and construction dust. |
| IEC60309 plugs & sockets: | Glass fibre reinforced polyamide, comply with IEC60309-1, IEC60309-2. IP44 protection when fully mated. |
| Circuit protection: | Thermomagnetic 4P MCB, IEC 60898 standard. |
| Internal bus & wiring: | T2 tin-plated copper terminals; 90°C heat-resistant flexible multicore cable. |
| Seals: | EPDM rubber gaskets for breaker window covers. |
4. Operating Conditions & Engineering Limitations
- Rated operating voltage: 380V ~ 415V AC, 50Hz
- Max continuous input current: 63A
- Single output circuit rated: 32A three-phase
- Ambient operating temperature: -10°C ~ +40°C
- Protection rating: Enclosure IP54; connected industrial sockets IP44
- Usage limitation: Classified as temporary mobile power equipment. Not permitted for permanent fixed building power distribution.
- Altitude: ≤1000m without current derating. Above 1000m, total load must be reduced by 5% per additional 500m.
- Environmental restriction: Not suitable for continuous exposure to heavy rain, corrosive chemical spray or flammable explosive atmosphere.
Common on-site mistake reminder: Many operators stack multiple heavy loads on one single phase. Users must evenly distribute load across L1/L2/L3 to restrict neutral current below 25A.
5. Standard On-Site Application Workflow
Step 1
Pre-commissioning inspection
Check enclosure integrity, seal condition, MCB trip function. Confirm all socket terminals have no loose wiring. Do not operate if cable insulation is damaged.
Step 2
Placement
Set unit on flat, solid ground. Avoid tilting. Do not submerge base in accumulated rainwater.
Step 3
Input connection
Connect generator or site mains feeder cable to the 63A 5P input plug. Lock plug twist ring fully.
Step 4
Power verification
Switch on power; measure L-L and L-N voltage with multimeter to check phase balance and phase sequence before connecting machinery.
Step 5
Load connection
Connect three-phase equipment to 32A outlets. Distribute loads evenly across three phases. Record load configuration for shift handover.
Step 6
Shutdown sequence
Disconnect all machinery loads → switch off all branch MCBs → disconnect incoming power plug → cover unused sockets.
Frequently Asked Questions
1: What risks does the built-in MCB protect against?
A: The 4-pole branch MCB provides overload protection and short-circuit protection for each 32A output. It does not include earth leakage protection. If personnel safety risk exists on site, add external RCD or select customized version with residual current devices.
2: Can this box be used continuously 24 hours a day?
A: Allowed for continuous operation within rated 63A total load. Operators must conduct thermal inspection every 4 hours to check plug and socket temperature. If surface temperature exceeds 55°C, reduce connected load.
3: What is the difference between this model and waterproof IP65 distribution boxes?
A: This unit has IP54 enclosure, prioritising compact mobility and easy breaker access. It can resist dust and splash water, but cannot withstand long-term heavy rainfall. For open-air uncovered sites, an IP65 sealed distribution box is recommended.
4: Is phase balancing required for operation?
A: Mandatory. Unbalanced three-phase loads will generate excess neutral current, cause internal overheating and accelerate insulation ageing. Maximum permissible phase current imbalance ≤15%.
5: Can we modify socket layout or add single-phase outlets?
A: Custom configuration is supported. Available upgrades: install 30mA RCD per circuit, add 16A single-phase blue sockets, fit digital voltage & current meters. Custom orders require minimum order quantity.
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