Reference Fig. 2.19, given that fault current = 2,000 A, Relay 1 set on 100%; CT ratio = 200/1; Relay 2 set on 125%. For discrimination the time gradient margin between the relays in 0.5 second. Determine the time of operation of the two relays assuming that both the relays have the characteristic as shows in the following table and the relay number, I has a time multiplier setting = 0.2. 200/1 R₂ 125 % 200/1 XM Plug setting multiplier Time in seconds for A time multiplier of 1 R₁ 100% 2 10 3.6 6 ไ 2000 A F 5 8 3.9 3.15 2.8 2.2 10 15 20 2.1

There is the connection scheme of a residual current device (RCD). The principle of operation: Under normal conditions, the current from L to N flows through the coils of RCD. The net magnetic flux in the circular core is zero, which results no current in the sensing coil. If any fault bypasses the coils, then the net magnetic flux is nonzero and a current is induced in the sensing coil. This makes the relay opens the switch. Let the source be 220V and the current through the load be 1 A. At some time, the test button becomes on and a current of 25 mA flows through the test button. i) Find the resistance through the test button and the load. ii) Does RCD opens the circuit if it operates for a differential current lager than 30 mA? Note: Assume that the coils on the circular core has zero resistance

Q19 Complete the answer : .............. transformer has double magnetic circuit.

List the materials used for construction of following parts (1) commutator (2) Transformer core (3) Yoke of DC machine (4) Armature and field winding

True or False 1. In solid grounding large fault current flows between the fault point and the grounded neutral.2. Solenoid relay works on the idea that an armature is attracted to the poles of an electro-magnet.3. The net force applied to the disc of an induction relay depends on the angle between the fluxes.4. In a watt-hour meter the secondary is connected to the relay. 5. Pickup current is the minimum current in a relay coil at which the relay starts to operate.

PLEASE HELP ME CHOOSE WHAT CORRECT LETTER OR ANSWER 1. The direction of induced voltage in a conductor can be changed by a. increasing the field strength. b. reversing the field direction. c. increasing conductor length. d. decreasing conductor size. e. reversing meter connections. 2. Direct current can be supplied to a load by a loop of wire rotating through a field with the use of a. slip rings. b. c. brushes. electromagnets. d. commutator. e. conductor. 3. Induced voltage can be increased in magnitude by a. increasing the number of lines cut per second. b. using a commutator. c. using slip rings. d. decreasing conductor length. e. properly applying the left-hand generator rule.

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Q7) Identify the following for the DC machine having a terminal voltage of 200V and a generated emf of 190V. a. DC motor b. DC generator c. DC motor and generator d. Not a DC motor or not a DC generator Clear my choice

What type of power losses does windage lods, bearing and brush friction is consid3red? a. stray losses b. armature losses c. core losses d. copper losses