Transformer
Understanding transformers, their operation, and applications.
What is a Transformer?
A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits. A varying current in any one coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (voltage) across any other coils wound around the same core. This principle is known as mutual induction.
How Transformers Work
Transformers operate on the principle of electromagnetic induction. They consist of two or more coils (windings) that are magnetically coupled, usually by a common iron core. When an alternating voltage is applied to the primary winding, it creates a changing magnetic flux in the core. This changing flux then induces an alternating voltage in the secondary winding.
Types of Transformers
| Type | Description | Application |
|---|---|---|
| Step-Up Transformer | Increases voltage from primary to secondary. | Power generation plants to transmit electricity over long distances. |
| Step-Down Transformer | Decreases voltage from primary to secondary. | Power distribution to homes and businesses, power adapters for electronics. |
| Isolation Transformer | Provides electrical isolation between circuits, often with a 1:1 turns ratio. | Safety in medical equipment, noise reduction in audio systems. |
| Autotransformer | Has a single winding with taps, used for small voltage adjustments. | Motor starting, variable AC power supplies (variacs). |
| Current Transformer (CT) | Used to measure high AC currents by stepping them down to a measurable level. | Electrical metering, protective relays. |
Transformer Equation (Ideal Transformer)
Where:
• Vp = Primary Voltage
• Vs = Secondary Voltage
• Np = Number of turns in primary coil
• Ns = Number of turns in secondary coil
• Ip = Primary Current
• Is = Secondary Current
Frequently Asked Questions
Why do transformers only work with AC?
Transformers rely on a changing magnetic flux to induce voltage in the secondary coil (Faraday's Law of Induction). Direct current (DC) produces a constant magnetic field, so it cannot induce a voltage in the secondary winding.
What is transformer efficiency?
Transformer efficiency is the ratio of output power to input power, typically very high (95-99%) for large power transformers. Losses occur due to resistance in windings (copper losses) and magnetic properties of the core (core losses).