Transformers Etc

Question 1

What is a current transformer.

Answer 1

A current transformer is a type of instrument transformer that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary.

Question 2

What is a voltage transformer?

Answer 2

Transformers (sometimes called “voltage transformers”) are devices used in electrical circuits to change the voltage of electricity flowing in the circuit. Transformers can be used either to increase the voltage (called “stepping up”) or decrease the voltage (“step down”).

Question 3

Function of a circuit breaker?

Answer 3

A spring loaded push switch will automatically be released when the circuit is exposed to a voltage which is too high. Circuit breakers can be switched back on unlike fuses which must be replaced.

Question 4

What is the function of an isolator?

Answer 4

Create a visible, permanent point of isolation on primary equipment for maintenance purposes and to route power flow. It is a manually operated mechanical switch that separates part of the electrical power.

Question 5

Function of busbars?

Answer 5

A conductor which allows multiple connections to the same source

Question 6

Function of fuses?

Answer 6

They have a built in weak point that will break when exposed to excess current flow. This will break the circuit. Blown fuses must be replaced. They are over current devices.

Question 7

Turn ratio formula?

Answer 7

Vp/Vs = Np/Ns 
Vp - voltage in the primary.
Vs - voltage in the secondary.
Np - number of turns on primary.
Ns - number of turns on the secondary.

Question 8

What are losses converted into?

Answer 8

Heat

Question 9

What is heat generated and transmitted through during losses?

Answer 9

Conduction
Convection
Radiation

Question 10

What is used to cool transformers?

Answer 10

Oil natural air forced

ONAF

Question 11

Linear loads?

Answer 11

Impedance stays the same with the voltage. Non linear are when impedance changes with the applied voltage.

Question 12

What should be able to carry normal current continuously?

Answer 12

Fuses

Question 13

Function of insulators?

Answer 13

To insulate the equipment from ground and other places.

Question 14

What is grounding?

Answer 14

To operate and maintain equipment safely to ensure that apparatus is dead, and there is no current flowing in the neutral conductor.

Question 15

What is an arrester?

Answer 15

To protect primary equipment of sudden overvoltage (such as a lightening strike)

Question 16

What is switchgear?

Answer 16

Integrated components to switch, protect, meter, and control power flow.

Question 17

What are reactors?

Answer 17

To limit fault current (series) or compensate for charge current.

Question 18

What is selectivity?

Answer 18

Trip the minimal amount to clear the fault or abnormal operating condition. As soon as excessive voltage comes through the system trips so it is efficient.