1. What Is Circulating Current In Parallel Transformers?

Circulating current is the current that flows between parallel-connected transformers due to voltage differences between their primary windings. This current circulates within the parallel connection without supplying any load current, potentially causing overheating and reduced efficiency.

2. How Does The Calculator Work?

The calculator uses the circulating current formula:

Where:

• \( I_{circ} \) — Circulating current (A)
• \( V_{primary1} \) — Primary voltage of transformer 1 (V)
• \( V_{primary2} \) — Primary voltage of transformer 2 (V)
• \( Z_1 \) — Impedance of transformer 1 (Ω)
• \( Z_2 \) — Impedance of transformer 2 (Ω)

Explanation: The circulating current is directly proportional to the voltage difference between transformers and inversely proportional to the sum of their impedances.

3. Importance Of Circulating Current Calculation

Details: Calculating circulating current is crucial for preventing transformer damage, optimizing parallel operation efficiency, and ensuring proper load sharing between transformers. Excessive circulating current can lead to overheating and reduced transformer lifespan.

4. Using The Calculator

Tips: Enter primary voltages in volts (V), impedances in ohms (Ω). All values must be positive, with impedances greater than zero. The calculator will compute the circulating current in amperes (A).

5. Frequently Asked Questions (FAQ)

Q1: What causes circulating current in parallel transformers?
A: Circulating current is primarily caused by voltage magnitude differences, phase angle differences, or impedance mismatches between parallel-connected transformers.

Q2: How can circulating current be minimized?
A: Use transformers with identical voltage ratios, similar impedances, and proper tap settings. Ensure transformers are properly synchronized before paralleling.

Q3: What are acceptable circulating current levels?
A: Generally, circulating current should be less than 10% of the rated current. Higher values may indicate improper paralleling conditions.

Q4: Can circulating current damage transformers?
A: Yes, excessive circulating current can cause overheating, increased losses, and potential damage to transformer windings and insulation.

Q5: Is this calculation applicable to three-phase systems?
A: This formula applies to per-phase calculations. For three-phase systems, calculate circulating current for each phase separately using phase voltages and impedances.