50 kva transformer max current single phase

The **maximum rated current** of a 50 kVA single-phase transformer depends on the **voltage level**, and the calculation formula is:

**Current (A) = Capacity (VA) ÷ Voltage (V)**

 I. Current Calculation of Single-phase Transformer (50 kVA)

II. Key Precautions

1. **Explanation of the Formula**:

   - The apparent power (kVA) of a single-phase transformer = Voltage (V) × Current (A), so the current is **inversely 

proportional** to the voltage.

   - **There is no need to consider the power factor** (kVA already includes the apparent power).

2. **Commonly Used Voltages in the United States**:

   - **120/240V Split Phase** (Single-phase three-wire system):

     - The current of the 240V winding is **208.33 A**, and the current of the 120V winding is **416.67 A** (the load needs 

to be balanced).

   - **480V Single-phase**: Commonly found in industrial equipment (such as welding machines).

3. **Overload Capacity**:

   - The transformer allows **short-term overload** (such as 10% to 20%), but **it must not exceed the rated current during

 continuous operation**, otherwise it will be damaged due to overheating.

III. Selection and Application Suggestions

- **Household/Commercial Scenarios** (240V):

  - Select a circuit breaker **above 208 A** (such as 225A), and match it with a #2/0 AWG copper cable (current-carrying 

capacity 215A).

- **Industrial Equipment** (480V):

  - With a current of 104 A, a 125A circuit breaker can be selected, and it is paired with a #1 AWG copper cable (current-carrying 

capacity 130A).

- **Voltage Matching**:

  - Be sure to confirm that the **rated voltage on the nameplate** of the transformer is consistent with the system (for example,

 for an isolation transformer with a 480V input and a 240V output, the current on the secondary side is 208A).

**Example**:

If the transformer is a **50 kVA, 240V single-phase** one, then the maximum continuous current is **208.33 A**, which is marked

 as **208 A** (rounded off).