CT Ratio Calculator
Calculate the CT secondary current from the primary current and the CT ratio, or find the correct CT ratio for your system. Includes formulas, tables, and examp...
ct secondary current from primary
div The CT ratio (Primary/Secondary) shows how high primary current can be safely cut to a normal secondary (1 A or 5 A). Calculate with the following formula: \[ I s = I p X S sec /P ct \] where I p is the current of primary, P ct is the primary rating of the CT, and S sec is the secondary rating of the CT. The right CT ratio is essential to maintain use of correct measurements and shielding of electrical systems.
Received Power Tool Formula:
The Received Power Calculator estimates the power received by an antenna or receiver in a wireless or RF communication system. Using the Friis transmission equation:
\[ P_{r} = P_{t} \times G_{t} \times G_{r} \times (\frac{\lambda}{4\pi R})^{2} \]
where P_r is received power, P_t is transmitted power, G_t and G_r are transmitter and receiver gains, λ is wavelength, and R is the distance between antennas. This calculator accounts for system losses, frequency, and antenna characteristics, helping engineers and students analyze link budgets and system performance. By inputting transmitted power, antenna gains, distance, and frequency, the tool instantly calculates received power in watts (W) or dBm. It’s ideal for RF design, Wi-Fi, satellite, and cellular system planning, ensuring reliable signal coverage, optimized transmission, and minimal interference.
⚡ Work & Installation Input to Output:
Received power represents the fraction of transmitted energy successfully captured by the receiving antenna. Inputs include transmit power, transmitter and receiver gains, frequency, and distance. The calculator outputs received power in W or dBm, considering free-space losses and antenna characteristics. This information is essential for RF link budgeting, system design, and ensuring sufficient signal strength for reliable communication.
Testing and Final Adjustments
After calculating received power, verify actual signal strength using a spectrum analyzer, power meter, or signal level meter. Compare theoretical calculations with measurements to account for environmental losses, interference, or multipath effects. Adjust transmitter power, antenna alignment, or system gains if the received power is below the required threshold. Periodic testing ensures communication reliability, reduces dropped connections, and improves system efficiency. Proper configuration based on the calculator helps in planning wireless networks, satellite links, or RF systems with optimal coverage and minimal power wastage.
Frequently Asked Questions - CT Ratio Calculator:
What does a CT ratio mean?
CT ratio Primary/Secondary shows how primary current is stepped down to a standardized secondary (e.g., 400/5).
How to get CT secondary current?
I_s = I_p × (S_sec / P_ct). Example: CT 400/5, I_p 200A → I_s = 2.5A.
What are common CT secondary ratings?
1 A and 5 A.
How to choose CT primary rating?
Pick CT primary ≥ expected max primary current and standard secondary (1/5A). Round up to next standard.
How to compute primary-equivalent from measured secondary?
I_p = I_s × (P_ct / S_sec).
Why choose 1A vs 5A secondary?
1A reduces burden current and wiring size; 5A is common for protection circuits.
What happens if CT is overloaded?
CT can saturate and give inaccurate readings; never open-circuit secondary under load.
Can CT ratio be fractional?
CT ratios are typically whole numbers; fractional secondary currents arise if primary current isn’t an integer multiple.
How to handle multiple primary turns?
Effective primary = N×current; formula applies using effective primary current.
Where to find CT standard sizes?
Refer to CT manufacturer catalogs; common primaries: 5,10,20,50,100,150,200,400,800 A etc.
