Copper loss is proportional to the square of load current. At half load, load current becomes half as voltage remains the same, so the copper loss will become (1/2)2 i.e 1/4 times of full load copper loss. At full load copper Loss = I2R At half load copper Loss = (I/2)2 × R = I2/4 × R 400 = I2/4 × R I2R = 4 × 400 I2R = Full load copper Loss = 1600 W
In Two wattmeter method the current coils of the wattmeter are connected with any two lines, say R and Y and the potential coil of each wattmeter is joined across the same line, the third line i.e. B as shown below in the figure . In the circuit B is the common point for both the wattmeter.
In the above option, the wood has the lowest calorific value. Its value is around 17000 – 20000 kilojoule/kg. The calorific value of LPG is 55000 kilojoule/kg. The calorific value of Kerosene oil is 45000 kilojoule/kg. The calorific value of hydrogen oil is 150000 kilojoule/kg.
Sudden changes of load on synchronous motors may sometimes set up oscillations that are superimposed upon the normal rotation, resulting in periodic variations of a very low frequency in speed. This effect is known as hunting or phase-swinging.
Galvanized steel conductors do not corrode, and possess high resistance. Hence such Wires are used in telecommunications circuits, earth wires, guard wire, stray wire, etc.
EXAMIANS