1. What is CT Ratio?

CT Ratio (Current Transformer Ratio) is the ratio of primary current to secondary current in a current transformer. It indicates how much the primary current is reduced to a standardized secondary current for measurement and protection purposes.

2. How Does the Calculator Work?

The calculator uses the CT Ratio formula:

Where:

• Primary Current — Input current to the transformer (amps)
• Secondary Current — Output current from the transformer (amps)

Explanation: The formula calculates the transformation ratio between the primary and secondary sides of a current transformer.

3. Importance of CT Ratio Calculation

Details: Accurate CT ratio calculation is essential for proper meter reading, protective relay operation, and overall electrical system monitoring and protection.

4. Using the Calculator

Tips: Enter primary current and secondary current values in amps. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What are typical CT ratios used in electrical systems?
A: Common CT ratios include 100:5, 200:5, 400:5, 800:5, 1200:5, and 2000:5, where the first number represents primary current and the second represents secondary current.

Q2: Why are CT ratios important in electrical metering?
A: CT ratios allow measurement of high currents using standard low-current meters by scaling down the actual current to a measurable range.

Q3: How does CT ratio affect meter readings?
A: Meter readings must be multiplied by the CT ratio to obtain the actual current values in the primary circuit.

Q4: What happens if the wrong CT ratio is used?
A: Using the wrong CT ratio will result in inaccurate measurements, potentially leading to incorrect billing, improper protection operation, or system monitoring errors.

Q5: Can CT ratio be changed after installation?
A: CT ratio is typically fixed based on the transformer's physical construction, but some multi-ratio CTs allow ratio changes through tap connections.