In a short circuit test on circuit breaker, time to reach the peak re-striking voltage is 50 µs with the peak restriking voltage of 100 kV. Determine average RRRV (Rate of rise re-striking voltage)?

RRRV = Peak value of restriking voltage/time to reach the peak re-striking voltage
RRRV = 100*1000/(50 μs)
RRRV = 2*10⁶ kV/sec

The single line diagram of the simple power system is shown in figure the corresponding reactance diagram is

Simple logic of reactance diagram is that simplified equivalent circuit of power system in which the various components of power system are represented by their reactances.
The reactance diagram can be obtained from impedance diagram if all the resistive components are neglected.

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A three-phase 400 V, 6-pole, 50 Hz squirrel-cage induction motor is running at a slip of 5%. The speed of rotor with respect to stator magnetic field and speed of the stator magnetic field with respect to rotor magnetic field are

Slip, s = (Ns - Nr)/Ns
Ns = 120f/P
0.05 = (1000 - Nr)/1000
Nr = 950 rpm
Speed of rotor with respect to stator magnetic field = 950 - 1000 = -50 rpm

Speed of the stator magnetic field with respect to stator core = 0
Speed of the rotor magnetic field with respect to rotor = sNs
Speed of the stator magnetic field with respect to rotor magnetic field = 0
Speed of the rotor magnetic field with respect to stator core = Ns

A power factor less than unity results in which of the following disadvantages?
(i) Large kVA rating of equipment
(ii)Poor voltage regulation
(iii) Greater conductor size

The load current is inversely proportional to the power factor, if power is constant
Lower the power factor, higher is the load current.
kVA rating of the equipment is inversely proportional to power factor.
The smaller the power factor, the larger is the kVA rating.
Therefore, at low power factor, the kVA rating of the equipment has to be made more, making the equipment larger and expensive.
To transmit or distribute a fixed amount of power at constant voltage, the conductor will have to carry more current at low power factor. This necessitates large conductor size.
The large current at low lagging power factor causes greater voltage drops in alternators, transformers, transmission lines and distributors. This results in the decreased voltage available at the supply end.

Transistors were used in ____ of Computers.