Variacs

Variacs, also known as variable autotransformers or variable transformers, are specialised electrical transformers with a single winding that serves as both the primary and secondary. This unique design results in smaller, lighter, and more cost-effective transformers compared to the conventional two-winding transformers. This shared winding provides inherent voltage regulation and isolation, although isolation is limited compared to a two-winding transformer.

Variacs allow for precise, continuous (smooth) control of output voltage, making them valuable tools in various applications, including motor speed control, laboratory testing, and voltage regulation. RS offers a wide range of variac transformers for sale at competitive prices, ensuring you find the perfect solution for your needs.

What Is a Variac Transformer?

A variac transformer, also known as an adjustable autotransformer or variable autotransformer, is an electromechanical device that allows for continuous adjustment of the output voltage from an AC power source. Unlike traditional transformers with isolated primary and secondary windings, a variac uses a single tapped winding. The output voltage is adjusted by moving a brush or carbon contact along the winding, varying the turns ratio. The term "variac" is a brand name that has become a generic term for variable autotransformers, derived from "variable alternating current."

Variac transformers are used to control the voltage of a power supply. They can be used to adjust the voltage supplied to equipment, or they can be used to test the effects of different voltages on equipment. Variacs are also useful for safely controlling voltages applied to sensitive electronic devices during testing.

There are several kinds of variac transformers, from single-phase to 3-phase. A 3-phase variac is a type of variable transformer designed to adjust the voltage of a 3-phase AC power supply. It can be used to control the speed of motors, the output of heaters, and the brightness of lighting systems, among other things.

Variac transformers are typically found in electronics labs and industrial settings where precise control over AC power is required. They can be used in applications such as testing electrical circuits, adjusting heating elements, and adjusting audio amplifiers.

How Does a Variac Work?

A variac is an AC power supply with an adjustable output voltage. Unlike a step-down transformer, it doesn’t reduce high-voltage AC mains (115/230V) to a fixed lower voltage. Instead, it provides a variable output voltage derived from the input AC voltage. The input AC voltage is applied across the entire winding, and the output voltage is taken from a variable tap on the same winding.

You control the output voltage by rotating a knob on the unit's front panel, which moves a carbon brush along the winding. This changes the number of turns in the secondary circuit, thus adjusting the output voltage.

All variacs are variable, offering a range of output voltages depending on the position of the brush. The output voltage range is typically from 0V up to, and sometimes slightly above, the input voltage. The upper limit of the output voltage is defined by its design specifications.

How to Choose a Variac

Choosing the right variac requires careful consideration of several factors to ensure compatibility, safety, and optimal performance:

• Determine Your Power Needs: Calculate the voltage and current requirements of the equipment you plan to power with the variac transformer. Ensure that the variac's voltage, current, and power ratings meet or exceed these requirements. It's always best to have some headroom.
• Single-Phase vs. Three-Phase: Determine whether you need a single-phase or three-phase variac transformer based on the power requirements of your equipment.
• Consider the Load Type: Different types of loads (e.g., resistive, inductive, capacitive) may require different types of variacs. Consult with a qualified electrician or engineer to determine the appropriate type for your application.
• Determine the Required Output Voltage Range: What is the minimum and maximum voltage you will need? Variacs typically offer a range from 0V up to, and sometimes slightly above, the input voltage.
• Multiple Outlets vs. Single Outlet: If you plan on using more than one piece of gear that requires a variac transformer, consider a model with multiple outlets. However, ensure that the total power draw of all connected devices does not exceed the variac's power rating.
• Safety Features: Look for variac transformers with built-in safety features such as overcurrent protection, thermal overload protection, and a robust enclosure.
• Consider the Environment: Choose a variac with an enclosure that is suitable for the intended environment. For example, if you plan to use the variac in a dusty or humid environment, choose a model with an appropriate IP rating.
• Portability: Benchtop models are common, but some portable units are available.
• Budget: Variacs range in price from relatively inexpensive to quite costly.
• Variable Frequency or Variable Voltage?: Variacs are generally for variable voltage only. Variable frequency is usually achieved through other means, such as a variable-frequency drive (VFD).

Industrial Application of Variac Transformers

Variac transformers are frequently used for:

• Motor Speed Control: Variacs are used to control the speed of AC motors by adjusting the voltage supplied to the motor.
• Laboratory Testing and Calibration: In laboratories, variacs provide adjustable voltage sources for testing and calibrating electronic equipment and components.
• Voltage Regulation: Variacs stabilise voltage levels in applications where fluctuations can affect equipment performance or cause damage.
• Power Supply for Equipment Testing: Variacs provide adjustable power sources for testing electronic devices and systems under different voltage conditions.
• Welding Machines: Variacs control the welding current in welding machines, allowing for precise adjustment of the welding parameters.
• Lighting Control Systems: Variacs adjust the brightness of lighting systems, creating different moods or energy-saving settings.
• Industrial Heat Treatment: Variacs control the temperature of heating elements in industrial heat treatment processes.
• HVAC Systems: Variacs regulate the speed of fans and motors in HVAC systems, optimising performance and energy efficiency.
• Electroplating: Variacs control the current and voltage in electroplating processes, ensuring consistent and high-quality plating results.
• Audio Equipment: Variacs are used in audio systems to adjust the volume and impedance of speakers, optimising sound quality.
• Medical Equipment: Variacs provide precise voltage control for sensitive medical equipment, ensuring safe and reliable operation.

Trusted Variac Manufacturer, Supplier & Distributor in Malaysia

RS is your trusted source for variac transformers in Malaysia. As a leading manufacturer, supplier, and distributor, we offer a wide selection of high-quality variac transformers from top brands like Carroll & Meynell and RS PRO. Our variac transformer prices also cater to diverse budgets. Buy your variac transformers from RS and experience quality, reliability, and expert advice.

Buy Variac Transformers Online from RS

Looking for a reliable variac transformer or a 3-phase variac? Buy your variac transformers online, along with current transformers and power supply cables, to ensure efficient and precise voltage control in your applications. We offer competitive prices and a seamless online ordering experience. Enjoy fast, nationwide doorstep delivery. For detailed delivery information and fees, visit our Delivery page.