How Does an Isolation Transformer Protect From Electric Shock in a Circuit?

Isolation transformers protect from electric shock

Most amplifiers are multistage amplifiers. Each stage is a small amplifier circuit. To get the desired power output, multiple stages are connected in a chain configuration. This means that the output of one stage becomes the input of the next stage. In the early days of multistage amplifiers, electric shocks and voltage surges became an increasing problem. If each stage of a multistage amplifier is connected directly to the next stage, an electric shock or power surge at the input could ripple through all of the stages causing serious damage. One solution to this problem is isolation transformers.

Function

Isolation transformers are designed to isolate or decouple two or more circuits. This allows both circuits to operate independently. This can be seen a lot in amplifier stages. By using isolation transformers, the only irregularities that can pass from stage to stage are signal irregularities.

Electric Shocks

An electric shock can be caused by many different things in today's high tech world. Static electricity is the most common cause of an electric shock. Moving across or coming in contact with various materials such as wool can cause a buildup of positive potential on the body. This buildup is looking for a path to the negatively charged ground. When the body gets close to the ground, a spark of static electricity is generated.

Damage

Electric shocks can damage and destroy electronic devices. Most electronic devices are designed to operate at low voltages. Sparks and shocks due to static electricity, power surges and lightning surges can generate voltages from 1,000 volts to more than 1,000,000 volts. Without insulation, these voltages and currents can ripple through all stages of the circuits.

Primary Coil

When a shock or voltage surge hits an isolation transformer, the current in the primary winding tries to rise very fast. The inductance of the primary coil opposes the change in current. This slows the rise and fall of the current. At the same time, the magnetic field of the primary coil will rise and fall. The rate at which the current in the primary coil changes will determine how much current makes it to the secondary coil. If the rate of change increases, more current will be induced into the secondary coil. If the rate of current change in the primary coil is reduced, less current is induced in to the secondary coil.

Secondary Coil

The magnetic field generated by the change in current in the primary coil now begins to induce a new current in the secondary coil. The inductance of the secondary coil also opposes to change in current which further reduces the rate of change of the current. The current that emerges from the secondary coil is has a reduced voltage and current compared to the initial shock that entered the system.

References

• All About Circuits: Electrical Isolation
• Epanorama: Isolator Transformer for Audio Lines