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How Does a Rectifier Work? - d8ou30 - 2021-08-30
How Does a Rectifier Work?
Rectifier, device that converts alternating electric current into direct current. It may be an electron tube (either a vacuum or a gaseous type), vibrator, solid-state device, or mechanical device. Direct current is necessary for the operation of many devices such as laptop computers, televisions, and certain power tools.
If only one polarity of an alternating current is used to produce a pulsating direct current, the process is called half-wave rectification. When both polarities are used, producing a continuous train of pulses, the process is called full-wave rectification.
You may wonder how power lines send electric currents across long distances for different purposes. And there are different "types" of electricity. The electricity that powers electric railway systems may not be appropriate for household appliances like phones and television sets. Rectifiers help by converting between these different types of electricity.
Bridge Rectifier and Rectifier Diode
AC DC rectifier lets you convert from alternating current (AC) to direct current (DC). AC is current that switches between flowing backwards and forwards at regular intervals while DC flows in a single direction. They generally rely on a bridge rectifier or a rectifier diode.
All rectifiers use P-N junctions, semiconductor devices that let electric current flow in only a single direction from the formation of p-type semiconductors with n-type semiconductors. The "p" side has an excess of holes (locations where there are no electrons) so it is positively charged. The "n" side is negatively charged with electrons in their outer shells.
Many circuits with this technology are built with a bridge rectifier. Bridge rectifiers convert AC to DC using its system of diodes made of a semiconductor material in either a half wave method that rectifiers one direction of the AC signal or a full wave method that rectifies both directions of the input AC.
Semiconductors are materials that let current flow because they're made of metals like gallium or metalloids like silicon that are contaminated with materials like phosphorous as a means of controlling current. You can use a bridge rectifier for different applications for a wide range of currents.
Bridge rectifiers also have the advantage of outputting more voltage and power than other rectifiers. Despite these benefits, bridge rectifiers suffer from having to use four diodes with the extra diodes compared to other rectifiers, causing a voltage drop that decreases the output voltage.
Silicon and Germanium Diodes
Scientists and engineers generally use silicon more frequently than germanium in creating diodes. Silicon p-n junctions work more effectively at higher temperatures than germanium ones. Silicon semiconductors let electric current flow more easily and can be created with lower costs.
These diodes take advantage of the p-n junction to convert AC to DC as a sort of electric "switch" that lets current flow in either the forward or reverse direction based on the p-n junction direction. Forward biased diodes let current continue to flow while reverse biased diodes block it. This is what causes silicon diodes to have a forward voltage of about 0.7 volts so that they only lets current flow if it's more than volts. For germanium diodes, the forward voltage is 0.3 volts.
The anode terminal of a battery, electrode or other voltage source where oxidization occurs in a circuit, supplies the the holes to the cathode of a diode in forming the p-n junction. In contrast, the cathode of a voltage source, where reduction occurs, provides the electrons that are sent to the anode of the diode.
Half Wave Rectifier Circuit
You can study how half wave rectifiers are connected in circuits to understand how they work. Half wave rectifiers switch between being forward biased and reverse biased based on the positive or negative half cycle of the input AC wave. It sends this signal to a load resistor such that the current flowing through the resistor is proportional to voltage.
You can measure the voltage across the load resistor as the supply voltage Vs, which is equal to the output DC voltage Vout. The resistance associated with this voltage also depends on the diode of the circuit itself. Then, the rectifier circuit switches to being reverse biased in which it takes the negative half cycle of the input AC signal. In this case, no current flows through the diode or the circuit and the output voltage drops to 0. The output current is, then, unidirectional.
Full wave rectifiers, in contrast, use the entire cycle (with positive and negative half cycles) of the input AC signal. The four diodes in a full wave rectifier circuit are arranged such that, when the AC signal input is positive, the current flows across the diode from D1 to the load resistance and back to the AC source through D2. When the AC signal is negative, the current takes the D3-load-D4 path instead. The load resistance also outputs the DC voltage from the full wave rectifier.
The average voltage value of a full wave rectifier is twice that of a half wave rectifier, and the root mean squared voltage, a method of measuring AC voltage, of a full wave rectifier is √2 times that of a half wave rectifier.
Rectifier Components and Applications
Most of the electronic appliances in your household use AC, but some devices like laptops convert this current to DC before using it. Most laptops use a type of Switched Mode Power Supply (SMPS) that lets the output DC voltage more power for the size, cost and weight of the adapter.
SMPS work using a rectifier, oscillator and filter that control pulse width modulation (a method of reducing the power of an electric signal), voltage and current. The oscillator is an AC signal source from which you can determine amplitude of current and the direction it flows. The laptop's AC adapter then uses this to connect to the AC power source and converts the high AC voltage to low DC voltage, a form it can use to power itself, during charging.
Some rectifier systems also use a smoothing circuit or capacitor that lets them output a constant voltage, instead of one that varies over time. The electrolytic capacitor of smoothing capacitors can achieve capacitances between 10 to thousands of microfarads (μF). More capacitance is necessary for greater input voltage.
Other rectifiers make use of transformers which alter voltage using four-layered semiconductors known as thyristors alongside diodes. A silicon-controlled rectifier, another name for a thyristor, uses a cathode and an anode separated by a gate and its four layers to create two p-n junctions arranged one on top of the other.
Uses of Rectifier Systems
The types of rectifier systems vary across applications in which you need to alter voltage or current. In addition to the applications already discussed, rectifiers find use in soldering equipment, electric welding, AM radio signals, pulse generators, voltage multipliers and power supply circuits.
Soldering irons that are used to connect parts of electric circuits together use half wave rectifiers for a single direction of the input AC. Electric welding techniques that use bridge rectifier circuits are ideal candidates for providing supply steady, polarized DC voltage.
AM radio, which modulates amplitude, can use half wave rectifiers to detect changes in electric signal input. Pulse generating circuits, which generate rectangular pulses for digital circuits use half wave rectifiers for changing the input signal.
Rectifiers in power supply circuits convert AC to DC from different power supplies. This is useful as DC is generally sent across long distances before it is converted to AC for household electricity and electronic devices. These technologies make great use of the bridge rectifier that can handle the change in voltage.
Electric vehicles have lots in common with gasoline-powered cars—room for four-plus passengers, range of several hundred miles, good safety—plus that one big difference: recharging with a plug at versus refueling from a pump. We’ve all pumped gas and know it’s a five- to 10-minute process; we suspect recharging takes longer and we know there are far fewer charging stations than the 125,000 U.S. public gas stations.
Here’s what you need to know about buying, installing and using the right EV charger. The more you know, the clearer it becomes that the unique aspects of EVs aren’t automatic disqualifiers.
Clearing Up the Range-Anxiety Misconception
With a gas-engine car, most owners drive until it’s low on fuel because gas stations are everywhere and gassing up is a quick stop. But empty-to-full charging is not what EV owners do most of the time. They top off every night or two, and as long as the car is charged in the morning, charging time doesn’t matter and range anxiety isn’t an issue for daily driving. Some use public charging, which means you do have to wait on the car. But 80% of charging is done at home, according to the JD Power U.S. Electric Vehicle Experience (EVX) Home Charging Study
Range and charging time may be less of an issue if an EV is the second car. If an EV is the only car, for long summer or holiday trip, owners can do what owners of compact gasoline-powered sedans may do: Rent a midsize or larger SUV for that two-week vacation. Or find a hotel with on-site charging.
For those who charge at home, you need to have the right charging equipment, and the proper electrical supply.
With EV charging, there isn’t a one-size-fits-all solution. Electric vehicles have different charging capabilities and requirements and every owner also has their own driving needs.
Here’s a look at key aspects of choosing the right charging equipment, installing it properly and best practices for using EV charging accessories at home.
Do You Need to Buy an EV Charger When One Comes Free?
Every electric car comes standard with a portable charger. (This thick cable that plugs into a wall outlet and the car counts as a charger.) However, every manufacturer provides a different unit, with varying levels of charging capabilities. In some cases, the same manufacturer provides different standard charging equipment depending on which of its EV offerings you purchase or lease.
EV charging connector types: what they are and how they compare
Moving to an EV from a petrol car is fairly straightforward. All the controls are in the same place, and the steering wheel hasn't changed into a large carrot or anything like that.
The thing that is different, however, is the fuel - and that means a new type of fueling connector. EV charging connector is broadly similar to a petrol hose - they're a pipe the electricity comes down - but there are three distinct types of charger, and they might need an adapter depending on what's fitted on your new electric car.
Those types are Rapid, which is the fastest. Fast, which is not the fastest. And Slow, which you probably get the idea about.
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Charging comes in either AC (for home chargers) or DC, and the amount of energy is measured in kilowatts.
Rapid chargers always have captive cables, so no need to bring your own, but the other kinds may require you to bridge the gap between charger and car yourself - your EV will come with a set of cables and adapters to do just this.
The market has yet to coalesce around one type of plug, and it can be quite complicated working out what goes where. We're here to help, and these are the most common connectors used on electric cars.
GB/T Charging Connectors
China, which has the world's largest electric car fleet, has its own charging connection. GB/T charging connectors again comes in AC and DC variants, the former with seven pins, and the latter with nine. Its plugs are circular, with a flattened edge, and larger than other types.
Type1 / CCS1 Conenctors
CCS, or combined charging system, is a beautifully elegant solution for fast DC charging. These are the original plugs, either Type 1 or Type 2, to which two more pins are added at the bottom. In the case of DC charging, these two lower pins participate in the charging itself and from the upper part only the communication pin and the earth conductor, which provides the reference point for the protection systems, are used. These connectors can withstand power of up to 350 kW.
It is currently the most popular type of DC connector. Type1 / CCS1 conenctors are common in the United States, while Type 2 CCS is used in Europe. The European Parliament's efforts to allow only CCS 2 and other plugs to be phased out of Europe have not been successful, but this standard is still winning, mainly because the car has only one socket. When using the CHAdeMO connector, the car must always have two sockets.
CCS are not compatible with CHAdeMO and GB / T charging stations because they use different communication protocolsa, so special adapters are needed and they are not easy to obtain.