# Rectifier Transformer – Working Principle and Application

- Link: https://studyelectrical.com/2015/11/what-rectifier-transformers-operation-and-application.html
- Published: 2015-11-25T08:03:00+00:00
- Author: 

## What is the Rectifier Transformer?

Rectifier transformers are different from normal power and distribution transformers
because they are special transformers made for industrial application. A Rectifier
transformer is a special application transformer which includes diodes and thyristors
in the same tank. 

Power electronic circuits that convert alternating current (ac) to direct current(
dc) is called rectifier circuits. Similarly, the circuits which can convert [direct current to alternating current](https://studyelectrical.com/2019/11/types-of-electric-current-steady-dc-varying-alternating-ac-current.html)
are called inverter circuits. Both of these circuits are considered to be converters.

**A transformer that has one of its windings connected to one of these converter
circuits, as a dedicated transformer, is a rectifier transformer or converter transformer.**

 

![Rectifier Transformers](https://studyelectrical.com/wp-content/uploads/2015/11/
Rectifier-Transformers.jpg "Rectifier Transformers")

Siemens Made Rectifier Transformers

_The figure shown is a Siemens made rectifier transformer used in an aluminium plant._

Some other special industrial purpose transformers are Electric arc furnace transformers(
EAF),  DC electric arc furnace transformers (DC EAF), Converter Transformers, Line
Feeders.

Read: [Substation Equipment and their working](https://studyelectrical.com/2019/04/electrical-substation-equipment-types-components-functions.html)

### Where Rectifier Transformers are Used?

Rectifier transformers are used for industrial processes which require a significant
direct current (dc) supply. Rectifier circuits are used to provide high-current 
dc for electrochemical processes like chlorine production as well as copper and 
aluminum production. 

Today, there are numerous applications that require transformers to supply rectifiers
with ever-increasing levels of power.

The classic example is provided by those industries that use electrolysis processes
for the production of aluminum, and the high secondary currents, together with the
harmonic currents generated by the rectification systems, must be taken into account
fully when designing transformers to power such loads.

Another typical use of rectifiers is in [electric traction](https://studyelectrical.com/2014/05/how-electric-locomotives-work.html)
systems in railways and subways.

They are also used in variable-speed-drive motor controls, transit traction applications,
mining applications, electric furnace applications, higher-voltage laboratory-type
experiments, [high-voltage direct-current power transmission (HVDC)](https://studyelectrical.com/2018/12/what-is-hvdc-transmission-system-components.html),
static precipitators, and others. 

### Operation of Rectifier Transformers

Two types of rectifiers are available: **thyristor rectifiers** and **diode rectifiers**.

In both cases, the transformers that power them must supply a gradually adjustable
secondary voltage, which is normally produced via on-load tap changers (OLTC).

In cases in which the range of secondary voltages is high, the variation is produced
through a regulation transformer, which can be located in a separate tank or in 
the same tank as the main transformer.

Rectifier transformers can be **liquid-immersed, dry-type, or cast-coil technology.**

Dry [type transformers](https://studyelectrical.com/2017/11/core-type-and-shell-type-transformers-comparison-application.html)
were primarily used in distribution-voltage classes.

Dry type and cast coil — are limited by voltage and kVA size. However, liquid-immersed
transformers can be built to all voltage levels and current levels. High-fire-point
fluids can be used for fire-protection considerations.

Voltage regulation is achieved with no-load or on-load tap changers on the high 
voltage side. Fine levels of voltage regulation can be achieved using saturable 
reactors on the secondary side. Regulation units may be built in or separate.

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