Variac transformer

It’s no surprise that many hardware hackers avoid working with AC, and frankly, we can’t blame them. The potential consequences of making a mistake when working with mains voltages are far greater than anything that can happen when you’re fiddling with a 3.3 V circuit. But if you do ever find yourself leaning towards the sparky side, you’d be wise to outfit your bench with the appropriate equipment. Take for example this look like a high-end piece of professional test equipment, but as the extensive write-up and build photographs can attest, this is a completely custom job. The downside is that this particular machine will probably never be duplicated, especially given the fact its isolation transformer was built on commission by a local company, but at least we can look at it and dream. This device combines two functions which are particularly useful when repairing or testing AC hardware. As a variable transformer, often referred to as a variac, it lets [Lajt] select how much voltage is passed through to the output side. There’s a school of thought that says slowly ramping up the voltage when testing an older or potentially damaged device is better than simply plugging it into the wall and hoping for the best. Or if you’re like Eddie Van Halen, you can use it to control the volume of your over-sized Marshall amplifiers when playing in bars. Secondly, the unit isolates the output side. That way if you manage to cross the wrong wire, you’re not going to pop a breaker and pl...

• Siglent Test Equipment • • • • • • • Rigol Technologies • • • • • • • • • Hantek Test Equipment • • • • Fluke Test Equipment • • • • ITECH Test Equipment • • • OWON Test Equipment • • • MG Chemicals • • • • • Pro's Kit • Elenco • • • • Snap Circuits® • ChipQuik • BlackJack Solderwerks • OSEPP • • • • • • • • • • • • Test Equipment • Bench Power Supplies • • • • Variacs (Variable Transformers) • Modular Power Supplies • • • • • • • • DC Electronic Loads • Programmable Power Supplies • Linear Power Supplies • Switching Power Supplies • DIN Rail Power Supply • Wall Power Supplies • Solar Cells & Solar Panels • Power Supply Accessories • Makerspace & DIY A variable transformer (also called a variac) is a very simple device to use. Its purpose is to raise or lower the voltage that enters it. Example: If your input voltage is too low - say 105 volts AC, you can just dial it up to the desired voltage, like 120 volts. If your input voltage is too high (130 volts AC) then you can lower it to your desired voltage (120 volts AC). It does not automatically adjust voltages. That would be a line conditioner and much more expensive. One application for a Another use is for cutting styrofoam. When a variacs output voltage passes through a nichrome wire it becomes heated and cuts the styrofoam like a hot knife through warm butter. Almost everyone is familiar with a dimmer switch in their home to adjust the light output of a bulb. A auto transformer variac does the same thing by varying ...

Transformers with Multiple Secondaries Transformer with multiple secondaries provides multiple output voltages. Here, three inductor coils share a common magnetic core, magnetically “coupling” or “linking” them together. The relationship of winding turn ratios and voltage ratios seen with a single pair of mutual inductors still holds true here for multiple pairs of coils. It is entirely possible to assemble a transformer such as the one above (one primary winding, two secondary windings) in which one secondary winding is a step-down and the other is a step-up. In fact, this design of transformer was quite common in vacuum tube power supply circuits, which were required to supply low voltage for the tubes’ filaments (typically 6 or 12 volts) and high voltage for the tubes’ plates (several hundred volts) from a nominal primary voltage of 110 volts AC. Not only are Photograph of a multiple-winding transformer with six windings, a primary and five secondaries. The transformer in the figure above is intended to provide both high and low voltages necessary in an electronic system using One transformer with multiple windings suffices elegantly to provide all the necessary voltage levels from a single 115 V source. The wires for this transformer (15 of them!) are not shown in the photograph, being hidden from view. If electrical isolation between secondary circuits is not of great importance, a similar effect can be obtained by “tapping” a single secondary winding at multiple poin...

• Siglent Test Equipment • • • • • • • Rigol Technologies • • • • • • • • • Hantek Test Equipment • • • • Fluke Test Equipment • • • • ITECH Test Equipment • • • OWON Test Equipment • • • MG Chemicals • • • • • Pro's Kit • Elenco • • • • Snap Circuits® • ChipQuik • BlackJack Solderwerks • OSEPP • • • • • • • • • • • • Test Equipment In the world of electric circuits and electric 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. There are a dozen different types of transformers out there; each one designed to fulfill unique or specific requirements. In this section, we’re covering variable voltage transformers—also known as “variacs.” What are Variable Voltage Transformers? Variable Voltage Transformers (also known as Adjustable Voltage Transformers) are transformers that can produce differing levels of output voltage from just one input voltage. These provide users with an efficient, trouble-free way to change 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. Th...

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