Transformers Exam Questions And Answers.

Transformers Exam Questions And Answers. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____. - Correct Answer ELECTROMAGNETIC INDUCTION. The energy is always transferred without a change in frequency, but usually with changes in _____ and _____. - Correct Answer VOLTAGE; CURRENT What is a transformer? - Correct Answer A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means. What is an ammeter? - Correct Answer An instrument used to measure electrical current. What are class 200 transformers? - Correct Answer Transformers with 4800 volt primaries and 120/240 volt secondaries, either pole or subway type, with two secondary windings terminating at internal links which provide for parallel operation of the secondary windings at 120 volts or series operation at 120/240 volts. Winding ration in series is 20:1 What are class 400 transformers? - Correct Answer Transformers designed for 4800 volt primary operation, but the secondaries are connected 240/480 volts. Winding ratio is 10:1 What are constant current transfomers? - Correct Answer A transformer which when supplied from a constant potential source automatically maintans a constant current in its secondary circuit under varying conditions of load impedance. Used on series street light circuits. What is a distribution transformer? - Correct Answer A transformer rated at 500KVA and below used for voltage transformation on the distribuition system. What is an Electromagnet? - Correct Answer A magnet made by winding a coil of wire around a soft iron core. Current passed through this winding produces magnetic lines of force in the coil. What is a fault? - Correct Answer A partial or total local failure in the insulation or continuity of a conductor. What is a flux? - Correct Answer The magnetic lines of force that flow from the north pole of a magnet and return to the south pole. What is a fuse? - Correct Answer A part of a circuit made of a low melting point material so that it will melt and break the circuit when a specified current exceeded. Always the weakest point in the circuit. What does grounded mean? - Correct Answer (Earthed) Connected to earth or to some conducting body which serves in place of the earth. What is a grounded system? - Correct Answer A system of conductors in which at least one conductors or point (usually the middle wire or neutral point of a transformer or generator windings) is intentionally grounded either solididly or through a current-limiting device. Anything above 600 volts is _____? - Correct Answer HIGH VOLTAGE What is Hysteresis? - Correct Answer The loss of power required to reverse the core magnatism each time the current reverses. This loss is caused by friction between the molecules of iron as these particles are aligned first in one direction and the in the opposite direct as current direction reverses. What is leg(s)? - Correct Answer Reference to a jumper or conductor, to or from a piece of electrical equipment. What is magnetic flux? - Correct Answer The total numbre of lines or force issuing from a pole. (north or south)