A variable transformer is a transformer that has the ability to put out a varying load of voltage from a similar input voltage. A variable transformer generally consists of a brush or a wiper which can be used to rotate across the windings in order to generate a variable turns ratio. A variable transformer is generally wired as an autotransformer without any electrical isolation that is between the output and the source. In simple words, in a variable transformer, there is no dual-coil core design. A variable transformer most of the time is controlled with the help of a dial. This dial gives the scope to get utilized like a lightning dimmer as well as in several other applications where accurate control over the quantity of the voltage that a load normally receives is required. A variable transformer is assembled less than 1 V/turn. This allows fine voltage adjustment.
A variable transformer substantially varies from standard transformers. There are some trade-marked versions of a variable transformer, also there are several other versions that are also available in the market as variable transformers, out of which some are built with custom specifications. These variable transformers are used widely for different types of applications. The most commonly used electrical components are mostly found in industrial settings and in residential settings. There are also some other variations of a variable transformer that has the scope of motorized control in order to allow adjustments from a distance.
Applications of a Variable Transformer
The usage of variable transformers is many varied; they are used in
- Generating variable DC voltage from an alternating current (AC) source is commonly done by controlling the input voltage to the rectifier elements.
- Correction of voltage in cases of over-voltage and under-voltage power supply that has 1, 2, or 3-phase circuits.
- Calibration of Control equipment and other electrical equipment.
- The regulation of servo motors.
- Manipulating the output voltage of a step transformer through controlling the input voltage.
- Speed control of electric motors (both AC and DC) such as the Fans that requires a low starting torque.
- Running electrical equipment and motors in a corrected voltage under scenarios where the input voltage is lower or higher than the rated voltage.
- When voltage is adjusted in a thermostatic control, it provides more uniform warming or heating. Hence variable transformers are used in heaters and even in oven temperature controls.
- The life span of a lamp increases significantly when it is operated in a voltage that it is rated for. Variable transformers are used in dimming and controlling the circuits of incandescence lamps, increasing their life span.
Uses of a Variable Transformer
A variable transformer is employed for the below mentioned:
- A variable transformer can be used in order to speed up as well as slow down the electric motors. This helps to make lights brighter and dimmer. It is also used to simulate some specific situations so that several testing activities can be carried out.
- During testing activities, a variable transformer can be used in order to change the voltage load on a circuit. This as result gives the scope to carry forward with testing even the voltage is lower than usual or even a situation when the voltage level is extremely low. Also, it allows increasing the voltage levels at which a certain electrical component being tested is generally designed for operating.
- In a variable transformer, the control knobs have the characteristics of allowing a continuous and smooth variation in voltage. This feature makes a variable transformer significantly different from any other digitally controlled devices that usually go up or down in the terms of output base.
- A variable transformer is not used as an isolating device. Rather a variable transformer is found in various devices where the separation from source voltage is not the point of concern. This is because the quantity of a voltage is provided to a load. All these devices come under the name of Variac which has been the most known electrical component to today’s date.
Three Phase Variable Transformer: An Overview
It is a type of autotransformer and is missing the dual-coil core design. These transformers come in one phase and three phases, with the three phases more prevalent. It works very simply as the knob for the transformer is rotated, the area that is connecting the brush with the coil gradually changes, the more the area of the contact the more is the voltage in the output. One of the significant functionality of a three-phase variable transformer is that the voltages can be changed very smoothly from zero to a voltage that is higher than the input voltage.
And quite obviously it is used in controlling the speed of motors or intensity of light sources. It is also used in scenarios where there is a need for different voltages such as testing devices for electrical and electronic equipment and apparatuses. It is to be noted that cannot be used as isolating devices. However, they can be used in numerous types of devices that keep the inputs independent from the other parts however needing control over the device.
A Variable transformer is best when it is built with the best quality of copper. Using the best quality of materials ensures that the transformers have relatively less amount of loss and drop of voltage. A good transformer ratio meter should be used to calculate the ratio as well as all other errors in various phases of a transformer. The entire procedure is automatic therefore removing all the scope of human error in making calculations and thus making it most desired and convenient.