What is CT formula?

What is CT formula?

CT ratio formula: CT ratio = I(P) / I(s) ————-1. Example: 1000:1. Here 1000 means it is a primary current and 1 means secondary current. Also, we can have rewritten as 1000/1.

What is the function of neutral CT in transformer?

Resolution: A Neutral Current Transformer encircles the neutral conductor (or is placed in-line on a bus); required on circuit breakers with Ground Fault Protection when applied on a grounded system.

What is CT ratio in transformer?

Ratio. The CT ratio is the ratio of primary current input to secondary current output at full load. For example, a CT with a ratio of 300:5 is rated for 300 primary amps at full load and will produce 5 amps of secondary current when 300 amps flow through the primary.

How is CT ratio of transformer rating calculated?

Definition: 1) The ratio of primary amps divided by secondary amps. 2) The current ratio provided by the windings of the CT. For example, a CT that is rated to carry 200 Amps in the primary and 5 Amps in the secondary, would have a CT ratio of 200 to 5 or 40:1.

What is ALF in CT?

The accuracy limit factor (ALF) of the CT is defined as the ratio of rated accuracy limit primary current to rated primary current. The protection class CT is marked as 5P10 or 5P20.

How do you calculate neutral current?

If A, B and C are the three phase currents, the formula to find the neutral current is the square root of the following: (A^2 + B^2 + C^2 – AB – AC – BC).

What is VK in CT?

According IEC, Knee Point Voltage of a Current Transformer is defined as the voltage at which 10 % increase in voltage of CT secondary results in 50 % increase in secondary current.

What is CT rating factor?

The basic formula for a 55°C rise CT is: Rating factor (RF) is a term, which applies to a current transformer. Typical rating factors of CT’s are 1.0, 1.25, 1.33, 1.5, 2.0, 3.0, and 4.0. Many times the manufacturer will only list the CT rating factor at 30°C ambient (room temperature).

What is the name of the neutral transformer?

The CT or Current Transformer connected to the neutral of a power transformer is called Neutral Current Transformer or Neutral CT or simply NCT. Whenever there is an unbalancing in between three phases of the power transformer, a resultant unbalance current flow through the closed path connected to the common terminals of the CT secondaries.

How to calculate the CT ratio of a transformer?

Let us take a simple example of a current transformer which is having CT ratio of 2000:1, assume that the CT primary has 1500Amps, calculate the secondary current with respect to the primary. The CT ratio is the inverse of the voltage ratio. If your transformer has a voltage ratio is 1:25 means, the CT ratio would be 25:1.

Which is the correct formula for the CT ratio?

CT ratio formula: CT ratio = I (P) / I (s) ————-1. Example: 1000:1. Here 1000 means it is a primary current and 1 means secondary current. Also, we can have rewritten as 1000/1.

Is there a maximum neutral current on a K-13 transformer?

Even in the widely used K-13 transformer, the associated load profile dictates only a maximum of a 126% neutral current.