Variacs

Product Information

Manual Variacs

In the world of electric circuits and electrical engineering projects, transformers are defined as passive electrical devices capable of transferring energy from one circuit to another circuit (or even to multiple other circuits). They typically have two or more wire coils and two circuits—a primary one and a secondary one.

What are Variable Voltage Transformers?

Variable Voltage Transformers (also known as Adjustable Voltage Transformers) are transformers that can produce different levels of output voltage from just one input voltage. These provide users with an efficient, trouble-free way to change the voltage in a short amount of time.

Compensation is one of the main reasons why people would want to change the secondary voltage so quickly. When the incoming line voltage changes, it’s best that the secondary voltage that serves the load remains regulated. This lessens the risk of intense fluctuation or continual voltage hunting conditions. This is why a voltage tolerance limit—from half a volt to a handful of volts—is maintained.

Variable voltage transformers are honestly the best choice for professionals and hobbyists who desire a more versatile option for changing the ratio between primary and secondary coils. They’re widely accessible, easy to operate, and (depending on the model and brand) can be highly intuitive. You can even program variable voltage transformers to automatically adjust to maintain constant or regular voltage output.

What are Variacs?

An “autotransformer” is a transformer that consists of only one coil shared by both the primary and secondary side of the circuit. The term “variable” in a variable autotransformer basically refers to the ratio of the primary windings to the secondary windings—i.e., the ratio of the secondary voltage to the primary voltage.

“Variac” is the generic name for variable autotransformers.

Variacs are arguably the most popular type of variable voltage transformers. They are AC power supplies that are cheaper, smaller, and a lot more portable than dual-winding transformers. They also have a number of useful casual and industrial applications that make them highly sought after.

Variac Structure

Although different types of Variacs will have variations in design, all models follow roughly the same basic structure.

Parts of a Variac/Variable Autotransformer :

How a Variac Works

Variable autotransformers have a single partially exposed winding the primary winding wrapped around a laminated magnetic core. There is a carbon brush (also known as the movable wiper) that is positioned in such a way that it can create an electrical connection with the winding. The transformer’s primary connection is made to both ends of the primary winding.

It is secondary connection called the common connection is made to just one end of the winding and is tapped through a movable carbon brush. This carbon brush can rotate or slide along the exposed section of the primary winding. The transformer’s ratio changes as the wiper moves.

Variable voltage transformers are typically designed with several primary windings enough to produce a secondary adjustable voltage that can be tuned from a few volts to fractions of a volt per turn. As long as the carbon brush is always in contact with the primary windings, the secondary voltage can be adjusted.

Common Applications for Variacs

There are a lot of common uses and practical applications for Variacs. As we mentioned earlier, they’re more portable and more cost-effective than regular AC power supplies, which pretty much makes them a top pick for short-term projects and casual hobbies. Variacs can be used to gradually revive previously dormant electronic equipment. They can also be used to regulate servo motors and control the temperature of ovens and heaters.

Voltage adjustment, when used with thermostatic control, provides more uniform heating.

You can also use Variacs to simulate various voltage and line conditions for experiments, or power electrical equipment designed for voltage that isn’t the typical 220V or 440V supplied domestically.

Advantages of Variacs/Variable Voltage Transformers

Affordable : As mentioned earlier, Variacs are affordable AC power supplies that are capable of fulfilling voltage needs and operating at the same level of transformers or power sources that go for four times its price.

Efficient : A Variac or autotransformer is much more efficient for voltage conversion compared to a two-winding transformer. This has to do with less ohmic loss and core loss thanks to the reduction of transformer material.

Effective : Variable voltage transformers or variable autotransformers are better at regulating voltage than an ordinary two-winding transformer of the same rating. This is due to their significantly lower drop in resistance and reactance.

Portability : Variable autotransformers are about half the size of a standard two-winding transformer. This makes them easier to handle. It also is partly why they’re much cheaper.

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