100kva transformer
The current calculation, selection suggestions and installation requirements for a 100kVA transformer (480V to 120V) are as follows:
I. Current Calculation and Selection
1. **Current on the Three-phase Primary Side (480V)**
2. **Current on the Single-phase Secondary Side (120V)**
3. **Correction for Practical Applications**
- For inductive loads (power factor 0.8): The secondary current is approximately 
.
- The selection needs to be adjusted according to the actual load characteristics.
II. Suggestions for the Selection of Core Equipment
1. **Circuit Breaker Specifications**
- **Primary Side**: Configure a 160A circuit breaker for three-phase (with a 20% margin reserved).
- **Secondary Side**: Configure a 1,000A circuit breaker for single-phase (it is recommended to use branch control, with each branch ≤ 200A).
2. **Cable Specifications**
- **Primary Side**: 16mm² copper-core cable (current-carrying capacity ≥ 150A).
- **Secondary Side**: 240mm² copper-core cable (current-carrying capacity ≥ 1,000A).
- **Parallel Scheme**: If the capacity of a single cable is insufficient, two 120mm² cables can be connected in parallel.
3. **Fuses**
- Primary Side: High-voltage fuse (150A); Secondary Side: Low-voltage fuse (1,200A).
III. Installation and Heat Dissipation Requirements
1. **Foundation and Space**
- The weight is approximately 250-300kg, and a concrete base (load-bearing capacity ≥ 500kg/m²) is required.
- Reserve an inspection passage of ≥ 1.5 meters around, and a heat dissipation space of ≥ 1 meter at the top.
2. **Heat Dissipation System**
- The full-load loss is approximately 800-1,200W, and forced heat dissipation is required:
- For indoor installation: Temperature-controlled fan (starts at 60℃) + independent exhaust system.
- For outdoor installation: IP55 protective enclosure + sunshade.
IV. Safety and Special Precautions
1. **Grounding and Protection**
- The grounding resistance of the neutral point ≤ 4Ω, and the enclosure grounding needs to comply with the GB 50169 standard.
- Protection level: IP23 for indoor use and IP55 for outdoor use.
2. **Vibration and Noise**
- Install anti-vibration rubber pads at the base, and control the noise ≤ 70dB (a soundproof cover is required in environmentally sensitive areas).
3. **Load Balance**
- The single-phase load needs to be evenly distributed to the three phases, and the current deviation ≤ 10%, otherwise it may lead to the deviation of the neutral point.
V. Compliance and Certification
1. **Standard Compliance**
- Installation in China needs to comply with the GB 50150 "Handover Test Standards for Electrical Equipment in Electrical Installation Works".
- Select products that have passed the CCC certification, and the no-load loss (≤ 300W) and load loss (≤ 1,200W) data need to be provided.
2. **Installation Qualification**
- The construction needs to be carried out by a licensed high-voltage electrician or an electrical engineering company, and a withstand voltage test (3,000V for 1 minute on the primary side) needs to be carried out after installation.
VI. Adaptation to Application Scenarios
- **Industrial Loads**: The power factor needs to be compensated to above 0.9 to avoid voltage fluctuations.
- **Data Centers**: It is recommended to configure an isolation transformer to prevent harmonic interference.
- **Emergency Power Supplies**: When used in conjunction with a generator, an automatic transfer switch (ATS) and anti-islanding protection need to be installed.
**Conclusion**: The current on the primary side of the 100kVA transformer is approximately 120A, and the current on the secondary side reaches 833A (which needs to be adjusted according to the load). When selecting, attention should be focused on the current-carrying capacity of the cable, the heat dissipation system and the load balance to ensure long-term stable operation. It is recommended to conduct an inspection once a quarter to check the tightness of the connection terminals and the temperature rise situation.
