75 kva transformer
A **75kVA three-phase transformer** is a high-capacity device designed to distribute or convert electrical power in industrial, commercial, or utility settings. Below is a detailed guide tailored to 75kVA three-phase transformers, covering technical specifications, applications, installation, and compliance with U.S. electrical codes (e.g., NEC 450).
*1. Core Function & Technical Basics**
- **Voltage Ratio**: Commonly used for **step-down** (e.g., 480V to 208V) or **step-up** (e.g., 208V to 480V) applications.
- **Phase Configuration**: Three-phase power delivers **higher efficiency** and **balanced loads** compared to single-phase.
- **Power Rating**: A 75kVA transformer supports up to **75,000VA** (or 75kW with a 1.0 power factor). For example:
- A 75kVA transformer can power a 60kW induction motor (60kW / 0.8 power factor = 75kVA).
- It can supply 100kW of lighting (100kW / 1.0 power factor = 100kVA), but this would exceed the transformer’s rating.
*2. Key Applications**
- **Industrial**: Large machinery (e.g., pumps, conveyor systems), welding equipment, and HVAC systems.
- **Commercial**: Office buildings, shopping centers, and data centers requiring stable three-phase power.
- **Utilities**: Substations and distribution networks for grid power.
*3. Technical Specifications**
| Specification | Typical Values for 75kVA Transformers |
| Voltage Ratings | 480V primary → 208V secondary (common in U.S.) |
| Efficiency | 98–99% at full load (e.g., Square D 75kVA) |
| Cooling Type | Dry-type (indoor use) or oil-cooled (outdoor/industrial) |
| Insulation Class | Class 150 (150°C rise) or Class 220 |
| Impedance | 4–6% (affects short-circuit protection) |
*4. Selection & Installation Tips**
- **Load Calculation**:
- **Three-Phase Power Formula**: `Power (kW) = (√3 × Voltage × Current × Power Factor) / 1,000`.
- **Example**: A 75kVA transformer with 480V primary and 208V secondary can supply `(75,000VA) / (√3 × 208V) ≈ 208A` per phase.
- **Voltage Drop**: Ensure voltage drop is ≤3% for critical loads (NEC 210.19).
- **Phase Balance**: Maintain **≤10% imbalance** between phases to prevent overheating.
*5. Safety & Compliance**
- **NEC Requirements**:
- **Overcurrent Protection**: Fuse or circuit breaker rated at 125–250% of the transformer’s full-load current (NEC 450.3).
- **Grounding**: Bond the secondary neutral to the ground (NEC 250.30).
- **OSHA Standards**: Install barriers for transformers over 600V (29 CFR 1910.303).
*6. Cost & Suppliers**
- **Price Range**:
- **New**: $5,000–$15,000 (e.g., [Square D 75kVA].
- **Refurbished**: $2,000–$8,000 (e.g., [Federal Pacific 75kVA].
- **Local Suppliers in Los Angeles County**:
- [Triad Magnetics] (custom solutions).
- [Pacific Transformer](industrial-grade models).
*7. Maintenance & Troubleshooting**
- **Routine Checks**:
- Inspect for overheating (touch-safe surfaces).
- Test insulation resistance annually.
- **Common Issues**:
- **Overheating**: Check for loose connections or undersized conductors.
- **Noise**: Tighten core laminations or replace bushings.
*8. Code Compliance in California**
- **Title 24**: Meet energy efficiency standards for transformers ≥50kVA (e.g., [DOE Efficiency Levels].
- **Fire Safety**: Install fire-resistant enclosures in high-risk areas (California Building Code, Title 24).
*9. Case Study**
A Los Angeles manufacturing plant installed a **75kVA dry-type transformer** ([Square D]to power a CNC machine and robotic arm. The installation included:
- **Surge Protection**: To protect against grid fluctuations.
- **Ventilation System**: Ensuring airflow for cooling.
*10. Key Considerations**
- **Future Expansion**: Choose a transformer with **10–20% headroom** for load growth.
- **Energy Efficiency**: Opt for [Energy Star-certified models] to reduce long-term costs.
For complex installations (e.g., paralleling transformers or high-voltage applications), consult a licensed electrical engineer. Always verify local codes (e.g., Los Angeles Municipal Code, Title 9) before installation.
