# Will wattmeter indicate power?

Last Update: May 30, 2022

This is a question our experts keep getting from time to time. Now, we have got the complete detailed explanation and answer for everyone, who is interested!

**Asked by: Miss Danielle Konopelski Sr.**

Score: 4.1/5 (31 votes)

The wattmeter is an **instrument for measuring the electric active power** (or the average of the rate of flow of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.

## What does a wattmeter indicate?

In a wattmeter, the **current coil helps in measuring current and the potential coil is used for measuring voltage**... but the real power that the wattmeter measures is V×I×cos(ϕ). How is the power factor involved in the measurement made by a wattmeter?

## How does a wattmeter measure power?

Each wattmeter **measures a line-to-line voltage between two of the three power supply lines**. In this configuration, the total power, watts is accurately measured by the algebraic sum of the two wattmeter values. Pt = P1 + P2. This holds true if the system is balanced or unbalanced.

## Which power does wattmeter reading indicate?

Wattmeter measures **the average power**.

So, wattmeter is a device capable of detecting voltage, current and the angle between the voltage and the current to provide power readings.

## Does wattmeter measure reactive power?

The voltage produces the pressure coil of wattmeter which is equal to the line voltage, but they have a phase shift of an angle of 90º. Similarly, the pressure coil of the Wattmeter 2 has the phase difference of 90º. **The arithmetic readings of both the Wattmeters gives the total reactive power of the circuit**.

## Two Wattmeter Method of Power Measurement - Three Phase Circuits - Basic Electrical Engineering

**21 related questions found**

### Can we measure reactive power?

**A single-phase varmeter (volt-ampere reactive meter)** is used to measure reactive power in single-phase circuits. Basically, it is an electrodynamic instrument, in which the voltage coil is made highly inductive reactance i.e., by replacing voltage coil resistance with an inductor.

### What is wattmeter Power Factor?

Definition: The instrument that **measures the low value of power factor** accurately is known as the Low Power Factor Wattmeter (LPFW). The low power factor meter is used for measuring the power of the highly inductive circuit. It is also used in the resistive circuit which has a power factor range from 0.5 to 1.

### What is apparent power?

Apparent Power is **the Total Power Flowing**

The total power flowing is known as the “apparent power” and is measured as the product of the voltage and current (V * I).. For example, if 208 volts and 5 amps are measured – the apparent power is 1040VA (VA means volt-amps – the measurement unit of apparent power).

### Why is MC short in wattmeter?

In principle the watmeter **must sense the voltage across the load and the current flowing through the load without disturbing them**. Then multiplies them and averages the the instantaneous power to get the effective power in the load. ... That it may be used to measure current only, voltage only or power.

### Which type of wattmeter is widely used?

The electrostatic wattmeter is suitable for high voltage low power factor circuits like dielectric loss measurement in capacitors. They are used in very small power measurements. The **induction type wattmeter** and pivoted coil direct reading wattmeters are very commonly used for power measurement.

### What is the power factor formula?

Power Triangle and Power Factor Summary

The power factor of an AC circuit is defined as the ratio of the real power (W) consumed by a circuit to the apparent power (VA) consumed by the same circuit. This therefore gives us: Power Factor = Real Power/Apparent Power, or **p.f.** **= W/VA.**

### What is the range of power factor?

The power factor can get values in the range from **0 to 1**. When all the power is reactive power with no real power (usually inductive load) - the power factor is 0. When all the power is real power with no reactive power (resistive load) - the power factor is 1.

### What determines how much a wattmeter needle will move?

The series coils measure current flowing through the circuit, the parallel coil measures voltage. A series resistor limits the current through the moving coil. It's situated between the two fixed coils and is attached to an indicator needle. **The magnetic fields in all three coils** influence the needle movement.

### What power factor means?

Power factor is an expression of energy efficiency. It is usually expressed as a percentage—and the lower the percentage, the less efficient power usage is. Power factor (PF) is **the ratio of working power, measured in kilowatts (kW), to apparent power**, measured in kilovolt amperes (kVA).

### What are different types of wattmeter?

**Types of Wattmeters**

- Ammeter. The technique used by an ammeter underlies most wattmeters. ...
- Digital Wattmeters. ...
- Professional Wattmeters.

### What is multiplying factor in wattmeter?

Multiplication factor of wattmeter is that parameter of virtue that helps us in finding a small scale wattmeter to get the power readings up to multiplication factor times that are multiplied to the smallest scale possible. ... It is also used in resistive current where its power factor range is from **0.5- 1**.

### What is the difference between UPF and LPF wattmeter?

Answer: **LPF wattmeter** is used to measure power in inductive circuits. Inductive circuits have the property of lagging power factor and hence these wattmeters are used. ... So UPF(Unit Power Factor) Wattmeter is used in SHORT CIRCUIT TEST of Transformer.

### Why do we use 2 wattmeter method?

Uses. The two wattmeter method is **used in determining total power derived from the three phase load which is always constant**, regardless of variations in phase power as well as angular displacement. Thus, the power output from a three-phase motor is also constant based on the findings using the said measurement.

### What is phantom load test?

Definition: Phantom loading is **the phenomena in which the appliances consume electricity even when they turn off**. The disc of the energy meter rotates which increases the reading of the meter, but the devices do not consume power. This type of loading is also known as the vampire or virtual loading.

### What is real and apparent power?

Ideal coils do not consume any electrical energy, but create a significant electric current. Real power is the power actually consumed due to the resistive load and **apparent power is the power the grid must be able to withstand**. The unit of real power is watt while apparent power unit is VA (Volt Ampere)

### How do you find apparent power?

Apparent power: **S = V x I (kVA)** Active power: P = V x Ia (kW)

### What is output apparent power?

The combination of reactive power and true power is called apparent power, and it is **the product of a circuit's voltage and current**, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S.

### Can we use wattmeter at home?

The wattmeter is used **for measuring the power of an electrical circuit**. It is also used for determining the power rating of the homes and industries appliances. The energy meter is used for measuring the total power consumed by the load in industries and homes.

### What will be the power factor in two wattmeter method when two wattmeter readings are equal?

Similarly, power measured by the wattmeter-2 is, W_{2} = V_{L} I_{L} cos(30 + 90) = -1/2 V_{L} I. Hence, at **zero power factor**, both the wattmeters indicate equal and opposite powers, so that their sum equals zero. Since wattmeter cannot show negative value as scale starts from zero.

### How many coils are in a wattmeter?

Generally, a wattmeter has **two coils** - Current coils and pressure or voltage coil. Using the current coil measures the flow of electric current, and using the pressure or voltage coil it measures the supply voltage. By combining the voltage and current, it measures the electrical power.