This document discusses methods for measuring power in three-phase electrical circuits. It describes the three wattmeter method, where a wattmeter is placed in each phase to measure the power individually, and the readings are summed to obtain the total power. The current coils of the three wattmeters are connected to the respective phases, while the pressure coils are all connected to the neutral point. Each wattmeter will display the power of that individual phase as the product of phase current and line voltage. Adding the three readings gives the total power of the three-phase circuit.
2. Power is measured in the electric circuits using a
Wattmeter.A single phase Wattmeter consists of
two coils,namely the curent coil and the pressure
coil.The current coil is connected is series with
line and thus carries the line current.The pressure
coil is connected in parallel with the line.The
wattmeter reading gives the power per phase
3. Power measurement in the 3-phase system
depends upon whether the load connected
across it is balanced or unbalanced and
whether it is in star or delta.Power in the
three-phase circuits is measured using the
various method
4. Various methods are used measurement of
three phase power inthree phase circuits on
the basis of number of wattmeter used. We
have three methods
1. Three wattmeters method
2. Two wattmeters method
3. Single wattmeter method.
6. Here, it is applied to three phase four wire
systems, current coil of all the three wattmeters
marked as one, two and three are connected to
respective phases marked as one, two and
three. Pressure coils of all the three wattmeter
are connected to common point at neutral line.
Clearly each wattmeter will give reading as
product of phase current and line voltage which
is phase power
7. . The resultant sum of all the readings of
wattmeter will give the total power of the circuit.
Mathematically we can write as
8. The power in a three-phase system may be
measured by placing a single-phase wattmeter
in each phase and adding the three readings.
This method is possible in a A system only if
the phase units can be separated and in a Y-
system only if the neutral or wye point can be
reached
