# Basics of Electrical Engineering

Learn the basics of Electrical Engineering.

A transformer is an electrical machine which changes the AC waveform from one voltage level to another.

Our electronic gadgets and power system utilize different types of the transformer for stepping voltages. The chargers of our mobile phone, laptop, and dc power supplies use transformers. In this article, you’ll learn about different types of electrical transformers.

### Step up and Step down transformer

A transformer can increase or decrease the magnitude of AC Voltages.
A step-down decreases the magnitude of output voltage as compared to primary.
For a step-down transformer, the number of windings on the primary side is larger than secondary.

A step up transformer, on the other hand, provides an output voltage that is higher than primary.
For a step up transformer:
Number of windings on primary < Number of windings on secondary

### Power Transformers

The electrical power system in the US is rated at 120 VAC. Electricity at the power station is generated at the voltage level of 11-25 kV. For purpose of transmitting it is then stepped up between 265-1000 kV. The receiving station on the other side then steps it down to 11 kV. Finally, the substation at the consumer end steps 11 kV to 120 VAC.

The stepping of voltage levels in our systems is carried through the Power Transformers. The stepping up of the voltage level at generating station is carried through the unit transformer. A transformer which performs stepping down from transmission levels to distribution levels is called the substation transformer. The other transformer which steps the 11 kV to 120 VAC is named as the distribution transformer.

### Instrumentation Transformers

A power system is rated at several thousand voltages. eg 500 kV, 132 kV, 765 kV, 1000 kV. Whereas, the voltmeters, ammeters, and relays deal with a fraction of these voltages. The higher voltage and current values are first stepped up using CTs (current transformers) and PTs (Potential Transformers). Since CTs and PTs protect our instruments against high values, they are also given the name protection transformers.

### Power Supply Transformers

The electrical voltage at our outlets is rated at 120 VAC. On the other hand, our electronic equipment including laptop, mobile phones, and tablets require dc values at lower levels (5 V, 15V, 11 V). This conversion from 120 VAC to 5VDC/11VDC or 15VDC is carried by using a DC power supply. A power supply transformer plays a vital role in stepping down the 120 VAC to smaller voltage levels. The lower magnitude of voltages is then rectified by using a diode bridge and is then fed to mobiles/laptops/tablets.

### Shell form and Rectangular form Transformers

Transformers are classified on the basis of core design.
A rectangular core transformer is simple in construction since it involves a simple core on which windings are wound on any two opposite directions. On the other hand, a shell form core has three legs. Both primary and secondary windings are wound on the central leg.