What is Meggar? Application and Operation of Meggar.

 Hello engineers, today we are going to discuss about meggar. This instrument has value in electrical maintenance field. Today we will learn basic of meggar. First of all we should know what meggar is? Well, if we define meggar in simple words, so,

Meggar is also known as megohmmeter, The megger insulation tester is an instrument used for measuring high resistances of the order mega ohms and for testing the insulation resistance of an insulated body.

If we talk about Meggar's operation, it uses a DC generator or a battery along with the electronic circuits. It is able to generate an output voltage up to 5000V (depending on the model of the instrument). The results depends upon the insulation resistance, which has an insulated element relating to an active element or a conductor. 

What is the Working Principle of Meggar?

Working principle of a "Megger, insulation tester" is based on the working principle of moving coil instruments, which states that when a current carrying conductor is placed in a magnetic field, a mechanical force is experienced by it. The magnitude and direction of this force depend upon the strength and direction of the current and magnetic field.

Construction of a Meggar Insulation Tester

The parts of Megger Insulation Tester are as listed below with diagram.

1. It consists of a hand driven DC generator and a direct reading ohm meter.
2. There are two coils A and B which are fixed together at some angle and are free to rotate about a common axis between the poles of a permanent magnet.
3. The coils are connected in the circuit by means of flexible leads (or ligaments) which exerts no restoring torque on the moving system.
4. The armature of the generator is rotated by the hand driven crank lever.
5. The clutch mechanism is designed to slip at a predetermined speed.
6. This facilitates the generator to maintain a constant speed and hence the constant voltage while testing.
7. The two coils A and B constitutes a moving coil voltmeter and an ammeter. Both are combined to form one instrument.
8. The hot terminal of the equipment whose insulation resistance has to be measured is connected to the testing terminal X. The terminal Y is connected to the body of the equipment, which is generally grounded.

Read: Ammeter, Working Operation and Constructions.

How does a Meggar Insulation Tester works?

When the crank handle is rotated, a voltage is generated in the generator. This generator voltage is applied across the voltage coil A through a resistance R1. This generator voltage is applied across the voltage coil A through a resistance R1.

Now, When the terminal X & Y are free initially, no current flows through the coil B. The torque produced by the coil A rotates the moving element to show infinity. Now while testing, the terminals X & Y are connected across the terminal and the body of the machine for measurement.

• The deflecting torque produced by the coil B interacts with the torque of coil A and rotates the moving element to indicate the resistance value.
• The volt generated by this instrument is around 500volts.
• Meggars are available to generate 100 volts, 2500 volts, and 5000 volts also. High voltage meggars are either motor-operated or power operated.

Advantages of Meggar

If we talk about the advantages of meggar tester, The advantages of the megger include the following.

• It can produce an accurate result
• It is very handy and easy to operate
• It can be used anywhere
• It can produce very quick results
• It is robust and safe to use

The Applications of Megger are,

• Used for the insulation of windings.
• Used to test electronic devices.
• Used to measure the resistance of insulators.

Now, for you, I have some questions, if you know, write the answers below in the comments section.

What is a bridge Megger?

How many terminals are in Megger?

What is an electrical Megger test?

Is a Megger AC or DC?

What is the use of guard in Megger?