208 to 480 transformer

The following is a summary of the core information about a **transformer converting 208V to 480V**, covering **type selection, 

parameter calculation, local solutions in the United States**, and **installation key points**, which will help you quickly match your needs:

 I. Core Types and Prices (US Market)

### II. Quick Model Selection Guide

1. Selection by Capacity and Load

- **Small Capacity (15~30 kVA)**

  - Select **Square D or Hammond dry-type transformers** ($1,800~$3,500), suitable for small motors and charging piles.

  - Current calculation:

    **Input current = 30,000VA ÷ (√3×208V) ≈ 83A**

    **Output current = 30,000VA ÷ (√3×480V) ≈ 36A**

- **Medium and Large Capacity (75~150 kVA)**

  - Select **Eaton oil-cooled type** ($6,000~$12,000), which supports outdoor installation and requires a cooling fan.

  - Note: For motor-type loads, a **20% derating** is required (for example, the actual available capacity of 75 kVA is 60 kVA).

 2. Selection by Voltage Connection Method

- **Common Configurations**:

  - **Input**: 208Y/120V (Three-phase four-wire, with a neutral wire)

  - **Output**:

    - **480Δ** (Three-phase three-wire, without a neutral wire, suitable for motors)

    - **480Y/277V** (Three-phase four-wire, with a neutral wire, suitable for mixed loads)

- **Error Risk**: If it is misconnected as **208Δ→480Y**, it will lead to an output voltage deviation of ±15%!

 III. Key Parameters and Installation Requirements

1. **Efficiency and Temperature Rise**

   - The efficiency of dry-type transformers is **95%~97%**, and the temperature rise under full load is ≤150°C (heat dissipation space needs to be reserved).

   - The efficiency of oil-cooled transformers is **98%+**, but the oil needs to be replaced regularly (once every 5 to 7 years).

2. **Dimension Reference (75 kVA Three-phase)**

   - Dry type: **30×20×37 inches** (Square D), weighing 544 pounds, suitable for indoor NEMA 1 environments.

   - Oil-cooled type: **49×37×46 inches** (Eaton), weighing 700 pounds, requiring an outdoor NEMA 3R base.

3. **National Electrical Code (NEC) in the United States**

   - The transformer needs to be grounded (**Clause 250.30**), and the neutral wire needs to be selected according to the **maximum phase current**.

   - For indoor installation, the distance from combustibles should be ≥**3 feet** (dry type) or **10 feet** (oil-cooled type).

 IV. Recommendations of Local Solutions in the United States

1. **Suppliers and Models**

   - **WESCO** (National Chain):

     - In-stock **GE 9T213BC3** (75 kVA, 208Y→480Δ, $4,200), and installation drawings are provided.

   - **Second-hand on eBay**:

     - Screen for second-hand transformers with **“UL Certification + 1-year Warranty”** (such as Federal Pacific T4T75-1, $1,500~$2,000).

2. **Installation Services**

   - Contact a **licensed electrician** to complete the wiring, and apply for an **electrical permit** from the local government (the fee is $200~$500).

   - Recommended service provider: **Wankong Electrical Services USA** (covering Washington and California).

V. Common Questions

- **Q: Can a single-phase 208V be converted to a single-phase 480V?**

  A: Yes, but a single-phase transformer (such as Hammond 167H) needs to be customized. Note that **a single-phase 208V is actually two phases of 208V** (not the line voltage), and the winding design needs to be confirmed with the supplier.

- **Q: How to test whether the transformer is working properly?**

  A: Use a multimeter to measure the output voltage. When it is no-load, it should be close to **480V±5%**, and the voltage drop after loading ≤**3%** is normal.

**Next Steps**:

1. Confirm the load type (motor/resistance) and connection method, and calculate the required capacity;

2. Contact **Wankong Electrical or a local electrician** to obtain a customized solution.