1. What is CT Ratio?

The CT (Current Transformer) ratio is the ratio of primary current to secondary current in a current transformer. It defines the transformation relationship between the primary and secondary currents.

2. How Does the Calculator Work?

The calculator uses the CT ratio formula:

Where:

• \( I_{primary} \) — Primary current (A)
• \( I_{secondary} \) — Secondary current (A)

Explanation: The ratio represents how much the current is stepped down from primary to secondary side of the transformer.

3. Importance of CT Ratio

Details: Accurate CT ratio is crucial for protection systems, metering, and monitoring in electrical power systems. It ensures proper current measurement and relay operation.

4. Using the Calculator

Tips: Enter primary and secondary currents in amperes (A). Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What are typical CT ratios?
A: Common ratios include 100:5, 200:5, 400:5, etc., where the secondary current is typically 5A or 1A.

Q2: Why is secondary current usually 5A or 1A?
A: Standardized secondary currents allow for interchangeable meters and relays in the system.

Q3: What happens if CT ratio is incorrect?
A: Incorrect ratio leads to inaccurate current measurements, affecting protection and metering.

Q4: Can this calculator be used for potential transformers?
A: No, this is specifically for current transformers. Potential transformers have voltage ratios.

Q5: How does burden affect CT ratio?
A: Excessive burden can cause ratio errors, but this calculator assumes ideal conditions.