Step down transformer

Learning Objectives By the end of this section, you will be able to: • Explain why power plants transmit electricity at high voltages and low currents and how they do this • Develop relationships among current, voltage, and the number of windings in step-up and step-down transformers Although ac electric power is produced at relatively low voltages, it is sent through transmission lines at very high voltages (as high as 500 kV). The same power can be transmitted at different voltages because power is the product I rms V rms . I rms V rms . (For simplicity, we ignore the phase factor cos Ï• . ) cos Ï• . ) A particular power requirement can therefore be met with a low voltage and a high current or with a high voltage and a low current. The advantage of the high-voltage/low-current choice is that it results in lower I rms 2 R I rms 2 R ohmic losses in the transmission lines, which can be significant in lines that are many kilometers long ( Figure 15.20 The rms voltage from a power plant eventually needs to be stepped down from 12 kV to 240 V so that it can be safely introduced into a home. A high-voltage transmission line allows a low current to be transmitted via a substation over long distances. Typically, the alternating emfs produced at power plants are “stepped up” to very high voltages before being transmitted through power lines; then, they must be “stepped down” to relatively safe values (110 or 220 V rms) before they are introduced into homes. The device that...

\( \newcommand\) • • Learning Objectives By the end of this section, you will be able to: • Explain how a transformer works. • Calculate voltage, current, and/or number of turns given the other quantities. Transformers do what their name implies—they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit (like that in Figure \(\PageIndex\] is the relationship between the output and input currents of a transformer. So if voltage increases, current decreases. Conversely, if voltage decreases, current increases. Example \(\PageIndex\): Transformers do not work for pure DC voltage input, but if it is switched on and off as on the top graph, the output will look something like that on the bottom graph. This is not the sinusoidal AC most AC appliances need. Example \(\PageIndex\))-- reasonable for good transformers. In this case the primary and secondary power is 240 W. (Verify this for yourself as a consistency check.) Note that the Ni-Cd batteries need to be charged from a DC power source (as would a 12 V battery). So the AC output of the secondary coil needs to be converted into DC. This is done using something called a rectifier, which uses devices called diodes that allow only a one-way flow of current. Transformers have many applications in electrical safet...

It means that a current gets induced in a coil when it comes in proximity to a current-carrying coil having varying magnetic flux. This induced current is directly proportional to the rate of change in current. Learn more about Faraday’s Law According to Faraday’s Law, any change in the magnetic field near the coil or conductor leads to the production of an electromotive force (EMF) that is induced inside the coil due to a change in magnetic flux. Transformer Construction A transformer consists of the following main parts: Core The coils that are winded up on a certain material collectively form a transformer core. These cores are made of very high permeable material that is able to carry the flux. The core of a transformer acts as a path or channel for the easy flow of magnetic flux. These cores are constructed using ferromagnetic materials that have high permeability such as iron. In transformers, we use thin metallic iron sheets instead of a single solid core because the single solid core causes a greater generation of eddy currents and this decreases the efficiency of a transformer. Winding The voltage transformers are winded with wires called coils. Here, we use wires with less resistance and good conductivity, which is required to get good efficiency from the transformer. Generally, copper is used in transformer winding as it has good electrical conductivity and very low resistance in comparison to others. It is also not expensive like gold, silver, and platinum. Tra...

• • by Last updated: August 23, 2021. The mighty power lines that criss-cross our countryside or wiggle unseen beneath city streets carry transformer. Let's take a closer look at how it works! Photo: A typical small electricity transformer supplying houses from the main power grid. Note the cooling fins (those vertical metal plates) on the four sides. Contents • • • • • • • • Why do we use high voltages? Your first question is probably this: if our homes and offices are using As Photo: Coming down: This old substation (step-down electricity transformer) supplies power in the small English village where I live. It's about 1.5m (5ft) high and its job is to convert several thousand volts of incoming electricity to the hundreds of volts we use in our homes. But there's another reason too. Industrial plants have huge factory machines that are much bigger and more energy-hungry than anything you have at home. The energy an appliance uses is directly related (proportional) to the voltage it uses. So, instead of running on 110–250 volts, power-hungry machines might use 10,000–30,000 volts. Smaller factories and machine shops may need supplies of 400 volts or so. In other words, different electricity users need different voltages. It makes sense to ship high-voltage electricity from the power station and then transform it to lower voltages when it reaches its various destinations. (Even so, centralized power stations are still very inefficient. About two thirds of the energy that a...

A transformer is an electrical device for safely "stepping up" or "stepping down" voltages to meet the incoming power requirements of connected equipment. Used in nearly every power distribution system application, they can range in size from several tons to tiny devices found in compact electronic equipment. Available are: • Ventilated general purpose transformers (NEMA Rated) • Encapsulated core general purpose transformers (NEMA Rated) • Encapsulated core buck-boost transformers (NEMA Rated) • Ventilated drive isolation transformers (NEMA Rated) • Open core industrial control transformers • Encapsulated core industrial control transformers HPS (Hammond Power Solutions) Sentinel series general-purpose ventilated transformers, available in various primary and secondary voltage configurations, feature an advanced core and coil construction that provides higher efficiency, resulting in low operating costs and more cooling savings due to lower heat emissions. • Dry-type 3-phase distribution transformer • Open coil/core ventilated • Meets DOE and NRCan requirements (federally mandated) • VA range from 15 to 75 kVA HPS drive isolation transformers are designed to meet the rugged demands of both AC and DC variable speed drives to provide required voltage changes and electrical protection. The separate primary and secondary windings provide electrical isolation between the incoming line and the VFD input. • Open core • 3-phase • 7.5 kVA to 220 kVA ratings Encapsulated distributi...