电气工程

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Electric machines and power electronics experiments involve electrical currents, voltages, power, and energy quantities that should be handled with extreme diligence and care. These may include three-phase AC voltage (208 V, 230 V, or 480 V), up to 250 V DC voltages, and currents that can reach 10 A. Electrocution occurs when an electrical path is established through the body with very low currents...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. The objective of this experiment is to achieve hands-on experience with different magnetic components from design and material perspectives. This experiment covers B-H curves of magnetic material and inductor design through identifying unknown design factors. The B-H curve of a magnetic element, such as an inductor or transformer, is a characteristic of the magnetic material forming the core around...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. DC/DC converters are power electronic converters that convert DC voltages and currents from a certain level to another level. Typically, voltage conversion is the main purpose of DC/DC converters and three main types of conversion exist in a single converter: stepping up, stepping down, and stepping up or down. Among the most common step-up converters are boost converters (Refer to this collections...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Boost converters provide a versatile solution to stepping up DC voltages in many applications where a DC voltage needs to be increased without the need to convert it to AC, using a transformer, and then rectifying the transformer output. Boost converters are step-up converters that use an inductor as an energy storage device that supports the output with additional energy in addition to the DC input...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. While it is simple to step up or down AC voltages and currents using transformers, stepping up or down DC voltages and currents in an efficient and regulated manner requires switching power converters. The DC/DC buck converter chops the input DC voltage using a series input switch, and the chopped voltage is filtered through the L-C low-pass filter to extract the average output voltage. The diode...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. A flyback converter is a buck-boost converter, which can both buck and boost. It has electrical isolation between the input and the output using a coupled inductor or a "flyback transformer." This coupled inductor enables a turns ratio that provides both voltage step-up and step-down capability, like in a regular transformer but with energy storage using the air-gap of the coupled inductor. The...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Transformers are stationary electric machines that step up or down AC voltage. They are typically formed of primary and secondary coils or windings, where the voltage on the primary is stepped up or down at the secondary, or the other way around. When a voltage is applied to one of the windings and current flows in that winding, flux is induced in the magnetic core, coupling both windings. With an AC...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. A DC power supply is generally considered to be a device that supplies DC, or unidirectional, voltage and current. Batteries are one such power supply, however, they are limited in terms of lifetime and expense. An alternative method to providing unidirectional power is to transform AC line power to DC power using a rectifier. A rectifier is a device that passes current in one direction, and blocks...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Similar to diodes, thyristors, also called silicon controlled rectifiers (SCRs), pass current in one direction from the anode to cathode, and block current flow in the other direction. However, current passage can be controlled through a "gate" terminal, which requires a small current pulse to turn on the thyristor so it can start conducting. Thyristors are four-layer devices, composed of alternating...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. DC power is unidirectional and flows in one direction, whereas, AC current alternates directions at a frequency of 50-60 Hz. Most common electronic devices are designed to run off of AC power; therefore an input DC source must be inverted to AC. Inverters convert DC voltage to AC through switching action that repeatedly flips the polarity of the input DC source at the output or load side for part of...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. The DC machine operates with DC currents and voltages as opposed to an AC machine, which requires AC currents and voltages. DC machines were the first to be invented and utilize two magnetic fields that are controlled by DC currents. The same machine can be easily reconfigured to be a motor or generator if appropriate field excitation is available, since the DC machine has two fields termed field...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. The objectives of this experiment are to find the equivalent circuit parameters of a three-phase induction motor using the per-phase equivalent circuit and tests similar to those used in transformer characterization. In electrical engineering, an equivalent circuit (or theoretical circuit) can be determined for a given system. The equivalent circuit retains all characteristics of the original system,...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Variable frequency drives (VFDs) are a type of adjustable speed drive, which are becoming standard equipment to power most AC induction motors. VFDs are common in industrial and automation applications and typically provide robust control of the motor in speed, torque, or position modes. The VFDs tested and simulated in this experiment focus on speed and open-loop control with constant voltage to...

Source: Ali Bazzi, Department of Electrical Engineering, University of Connecticut, Storrs, CT. Three-phase wound-rotor synchronous generators are the main source of electrical power worldwide. They require a prime mover and an exciter in order to generate power. The prime mover can be a turbine spun by fluid (gas or liquid), thus the sources of the fluid can be water running off a dam through a long nozzle, steam from water evaporated using burned coal, etc. Most power plants including coal,...

来源：Ali Bazzi，康涅狄格大学电气工程系，斯托尔斯，康涅狄格州。 三相绕线转子同步电动机由于转子磁场需要电刷，因此不如永磁转子同步电动机普及。同步发电机则更为常见，大多数现有的发电厂都采用此类发电机，因为它们具有优异的频率和电压调节性能。同步电动机的优点在于其转速调节几乎为0%，这是因为转子转速与定子磁场转速完全相同，使得转子转速保持恒定，不受电机轴负载大小的影响。因此，它们非常适用于恒速运行的应用场合。