09-04-2012, 04:29 PM
VOLTAGE REGULATORS
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INTRODUCTION
It a voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. Ideally, the output of most power supplies should be a constant voltage. Unfortunately, this is difficult to achieve. There are two factors that can cause the output voltage to change. First, the ac line voltage is not constant. The so-called 115 volts ac can vary from about 105 volts ac to 125 volts ac. The ac line voltage alone can be responsible for nearly a 20 percent change in the dc output voltage. The second factor that can change the dc output voltage is a change in the load resistance. In complex electronic equipment, the load can change as circuits are switched in and out. In a television receiver, the load on a particular power supply may depend on the brightness of the screen, the control settings, or even the channel selected.
NEED OF VOLTAGE REGULATION
1. Utility Voltage Level: Anyone receiving power from an electric utility will see the nominal incoming voltage level (230V) change over the course of a day to a small or large degree. There are many factors contributing to the amount of voltage level fluctuation observed including: 1) location on the local distribution line, 2) proximity to large electricity consumers, 3) proximity to utility voltage regulating equipment, 4) seasonal variations in overall system voltage levels, 5) load factor on local transmission and distribution system, etc. Most electric utilities in the U.S. try to maintain the voltage level within plus or minus 5% of the nominal voltage level ( 230V +/-5%), however for short periods the voltage level may be as much as 6% high or 13% low .
IMPORTANT METHODS OF VOLTAGE REGULATION
1. CONTROL GENERATOR VOLTAGE: There are several types of voltage regulators (Vibrating –contact type regulator, Rheostatic type regulators). All of them works on the principle of short circuiting a part of the generator field resistance thereby raising the excitation of the generator , to compensate for the voltage drop in voltage due to increase in load. The rise and fall in voltage itself is utilized to do this automatically, so as to maintain the voltage nearly constant whatever may be the variation in load.
ELECTONIC VOLTAGE REGULATORS
The electronic voltage regulator (EVR) has evolved with the advancements in power semiconductors over the past 20 years. Unlike the mechanical voltage regulator, the electronic voltage regulator is only used in power quality applications since it is designed
USE OF TAP CHANGING TRANSFORMER : The voltage can be varied by having a number of tapping on secondary winding so that turn ratio can be changed at will The tapings may be changed on load but where quick change without break in circuit is required on load tap changing transformer either alone or in conjunction with auto transformer are employed.
3. USE OF BOOSTER TRANSFORMERS : The advantage of booster transformer is that these are cheaper when there is no main transformer at the point where voltage regulation is required.
4. PHASE ANGLE CONTROL : In interconnected system it is necessary to control both the magnitude and phase angle of various line voltage for load dispatching. Various methods such as induction regulators , power factor control , in phase/or quadrature voltage boosters transformers are employed.
AUTOMATIC VOLTAGE REGULATOR
The automatic voltage regulator or AVR is a class of devices that provide constant voltage levels to prevent malfunctions or damage to downstream electrical equipment. The automatic voltage regulator or AVR, as the name implies, is a device intended to regulate voltage automatically: that is to take a varying voltage level and turn it into a constant voltage level. AVRs range in size from small ones that can be mounted on printed circuit boards to those the size of a small house.
ADVANTAGES OF VOLTAGE REGULATORS
1 . This technology deliver increased reliability in a quiet ,compact package and is lower in
cost.
2 . Clean conditioned power improves equipment performance .
3 . Protects equipments from potentially harmfull daily electrical events.
4 . Automatically shuts down in event of voltage exceeding certain value.
CONCLUSION
The output of most power supplies should be a constant voltage but power system consist of various voltage fluctuation due varying load . These voltage fluctuations may causes serious damage to the electrical equipments and which may add extra cost to utility. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. It can be used for both ac or dc voltage regulator depeding upon needs. By using different types of voltage regulators we can save many electrical equipments from damaging. Voltage regulators provide safer operation and reliable operation of equipments at low cost .