Impulse Generator

Introduction

In the field of high voltage engineering, an impulse generator plays a crucial role in generating impulse voltage waves for various testing purposes. This topic will cover the fundamentals of generating impulse voltage waves, the reasons for adopting a particular shape for these waves, and the analysis and control of impulse generator circuits.

Key Concepts and Principles

Specifications of an Impulse Voltage Wave

An impulse voltage wave is characterized by several specifications:

1. Peak value: The maximum amplitude of the voltage wave.
2. Front time: The time taken for the voltage wave to rise from 10% to 90% of its peak value.
3. Time to half value: The time taken for the voltage wave to decrease from its peak value to half of its peak value.
4. Tail time: The time taken for the voltage wave to decrease from half of its peak value to 10% of its peak value.

Standard Impulse Wave Shapes

There are two commonly used standard impulse wave shapes:

1. 1.2/50 μs wave: This wave has a front time of 1.2 microseconds and a tail time of 50 microseconds.
2. 8/20 μs wave: This wave has a front time of 8 microseconds and a tail time of 20 microseconds.

Analysis and Control of a Simple Circuit of an Impulse Generator

An impulse generator consists of two main circuits: the charging circuit and the discharging circuit.

1. Charging circuit: This circuit is responsible for charging the energy storage element, such as a capacitor, to a high voltage level.
2. Discharging circuit: This circuit is responsible for discharging the energy storage element through the test object, generating the impulse voltage wave.

Multistage Impulse Generator (Marks Circuit) Working

The Marks circuit is a commonly used multistage impulse generator. It consists of multiple stages, each consisting of a charging circuit and a discharging circuit. The operation of each stage is synchronized to generate a high voltage impulse.

Earthing and Tripping in Impulse Generators

Proper earthing is essential for the safe operation of impulse generators. It helps to prevent electrical shocks and ensures the safety of personnel. Tripping mechanisms are also incorporated in impulse generators to automatically disconnect the power supply in case of any fault or abnormal condition.

Techniques to Observe Wave Front on a Cathode Ray Oscilloscope (C.R.O.)

To observe the wave front of an impulse voltage wave on a Cathode Ray Oscilloscope (C.R.O.), the C.R.O. is connected to the impulse generator. Adjustments and settings are made on the C.R.O. to accurately observe the wave front.

Step-by-step Walkthrough of Typical Problems and Solutions

Problem: Inadequate Peak Value of Impulse Voltage Wave

If the peak value of the impulse voltage wave is inadequate, it can be adjusted by modifying the parameters of the charging circuit. This may involve changing the capacitance or the charging resistance.

Problem: Improper Wave Shape of Impulse Voltage Wave

If the wave shape of the impulse voltage wave is not as desired, it can be modified by changing the components in the discharging circuit. This may involve adjusting the resistance or the inductance.

Problem: Unstable Operation of the Impulse Generator

If the impulse generator is not operating stably, it may be due to faulty components. Checking and repairing these faulty components can help restore the stable operation of the impulse generator.

Real-world Applications and Examples

Impulse generators find applications in various areas, including:

Testing Insulation Strength of High Voltage Equipment

Impulse generators are used to test the insulation strength of high voltage equipment, such as transformers and cables. By subjecting the equipment to high voltage impulses, their insulation capabilities can be evaluated.

Lightning Protection System Testing

Impulse generators are used to test the effectiveness of lightning protection systems. By generating lightning-like impulses, the response of the protection system can be analyzed.

High Voltage Laboratory Experiments

Impulse generators are extensively used in high voltage laboratory experiments to study the behavior of electrical systems under high voltage conditions.

Advantages and Disadvantages of Impulse Generator

Advantages

1. Ability to generate high voltage impulses for testing purposes: Impulse generators provide a reliable and controlled method of generating high voltage impulses, which are essential for testing the insulation strength of electrical equipment.

2. Versatility in generating different wave shapes: Impulse generators can be designed to generate different wave shapes, allowing for a wide range of testing scenarios.

Disadvantages

1. Complex circuitry and maintenance requirements: Impulse generators involve complex circuitry, requiring skilled personnel for operation and maintenance.

2. Potential safety hazards if not operated properly: Impulse generators operate at high voltages and can pose safety hazards if not operated with proper precautions.

Summary

An impulse generator is a crucial tool in high voltage engineering for generating impulse voltage waves. It is characterized by specifications such as peak value, front time, time to half value, and tail time. Standard impulse wave shapes include the 1.2/50 μs wave and the 8/20 μs wave. Impulse generator circuits consist of a charging circuit and a discharging circuit. The Marks circuit is a commonly used multistage impulse generator. Proper earthing and tripping mechanisms are important for safety. Techniques to observe the wave front on a C.R.O. are employed. Typical problems with impulse generators include inadequate peak value and improper wave shape, which can be solved by adjusting circuit parameters. Impulse generators find applications in testing insulation strength, lightning protection system testing, and high voltage laboratory experiments. They offer advantages such as the ability to generate high voltage impulses and versatility in generating different wave shapes, but also have disadvantages such as complex circuitry and potential safety hazards if not operated properly.

Analogy

Imagine an impulse generator as a powerful wave generator in a water park. The generator can create different types of waves with specific shapes and sizes. These waves are used to test the strength of various water slides and structures in the park. The generator has complex controls and safety mechanisms to ensure the waves are generated accurately and safely.