Monday, April 4, 2011

SEPARATION OF NO LOAD LOSSES IN A SINGLE PHASE TRANSFORMER

SEPARATION OF NO LOAD LOSSES IN A SINGLE PHASE TRANSFORMER
AIM:
To separate the eddy current loss and hysteresis loss from the iron loss of single phase transformer.

APPARATUS REQUIRED:
 S. No. Name of the Apparatus Range Type Quantity 1 Rheostat 1250Ω , 0.8A Wire Wound 2 2 Wattmeter 300 V, 5A LPF 1 3 Ammeter (0-2) A MC 1 4 Voltmeter (0-300) V MI 1 5 Connecting Wires 2.5sq.mm Copper Few

PRECAUTIONS:
1.    The motor field rheostat should be kept at minimum resistance position.
2.    The alternator field rheostat should be kept at maximum resistance position.

PROCEDURE:
1.    Connections are given as per the circuit diagram.
2.    Supply is given by closing the DPST switch.
3.    The DC motor is started by using the 3 point starter and brought to rated speed by adjusting its field rheostat.
4.    By varying the alternator filed rheostat gradually the rated primary voltage is applied to the transformer.
5.    The frequency is varied by varying the motor field rheostat and the readings of frequency are noted and the speed is also measured by using the tachometer.
6.    The above procedure is repeated for different frequencies and the readings are tabulated.
7.    The motor is switched off by opening the DPST switch after bringing all the rheostats to the initial position.

TABULAR COLUMN:

 S.No. SpeedN (rpm) Frequencyf (Hz) VoltageV  (Volts) WattmeterreadingWatts Iron lossWi (Watts) Wi / f Joules

FORMULAE USED:
1.    Frequency, f =(P*NS) / 120  in Hz P = No.of  Poles  &     Ns = Synchronous speed in rpm.
2.    Hysteresis Loss Wh = A * f in Watts        A = Constant (obtained from graph)
3.    Eddy Current Loss We = B * f2  in Watts  B = Constant (slope of the tangent drawn to the curve)
4.    Iron Loss Wi = Wh + We  in Watts            Wi / f  = A + (B * f)
Here the Constant A is distance from the origin to the point where the line cuts the Y- axis in the graph between Wi / f  and frequency f. The Constant B is                 Δ(Wi / f  ) / Δf

MODEL GRAPH:

RESULT:
Thus separation of eddy current and hysteresis loss from the iron loss on a single-phase transformer is conducted.