Chapter 3 Control of Induction Motors and DTC 3.1 Introduction Induction motors are the mostly used types of motors nowadays in different industries. The spread of such types of motors is due to their simple construction and high performance. In contrary to the DC motors that need more service and extra costs, the induction motors are less costly and need less maintenance during their function life. The main advantage of DC machines over AC machines is the ease of control of these machines. With the development of semiconductor industries and power electronic switching devices, the control of induction machines is becoming more and more simple and feasible. Different control methods of induction machines have been proposed like voltage …show more content…
The relation between the frequency and the speed is proportional as seen from the last equation. Decreasing the frequency under constant voltage will lead to the saturation of the air gap, the torque will be increased and the speed will fall. If the frequency is increased, the speed will increase and the developed torque will be decreased. This method is rarely used in the control of induction motors due to the magnetic saturation which causes high currents and losses. Figure 3.2 shows the curve of speed torque control by frequency variation. The developed torque decreased under higher frequencies while it increases with low speeds. Figure 3.2: Torque speed characteristics with variable frequency control. 3.2.3 Voltage/frequency Control of induction …show more content…
3.2.7.5 Torque and flux reference generation The control of induction motor speed implies the measurement of the speed. The measured speed is compared with the desired speed. The error between desired speed and actual speed is fed to a speed controller whose output determines the torque reference of the induction motor. Figure 3.12 shows the speed control of induction motor and torque reference generation. Figure 3.12: General structure of DTC control including the use of a controller. 3.3 Voltage source Inverter The voltage source inverter produces voltage vectors controlled by the lookup table block. The idea of the VSI is to switch positive and negative voltages on and off in high frequency to produce the required AC voltage. It is used in generating AC voltage from DC source or apacitor bank. The VSI is composed mainly of six power switchs controller in openning and closing; these switches are connected in anti parallel with recovery diodes. Figure 3.13 presents the general structure of a simple voltage source inverter (Rashid,
3. As engine speed increases above engagement, the primary clutch squeezes together some more and pushes the belt so that it moves to a larger radius on the primary. Because the two clutches rotate about fixed points, the belt gets pulled into the secondary, spreading it farther apart and moving the belt to a smaller radius.
The experiment test-bed is composed of a DC motor, an engine, a chain drive, a shaft and other accessorial components. The DC motor is used to drive the engine shaft and its speed can be up to 1450 r/min.
Rockis, Gary, and Glen Mazur. Electrical Motor Controls for Integrated Systems. 4th ed. Homewood, IL: American Technical, 2009. Print
Just about 80% of the mechanical power utilized by businesses is given by three stage enlistment engines in view of its basic and tough development, ease, great working attributes, nonappearance of commutator and great speed direction. In three stage enlistment engine the power is exchanged from stator to rotor twisting through acceptance. The Enlistment engine is likewise called offbeat engine as it keeps running at a speed other than the synchronous speed. Like some other electrical engine enlistment engine additionally have two primary parts to be specific rotor and stator. A 3-stage enlistment engine has two principle parts (I) stator and (ii) rotor. The rotor is isolated from the stator by a little air-crevice which ranges from 0.4 mm to 4 mm, contingent upon the force of the engine. The primary body of the Enlistment Engine involves two noteworthy parts as shows in Figure
When one hears the name Nikola Tesla, the idea of a great inventor usually does not pop into one’s head instantaneously. In fact, in most cases the person doesn’t know who that is. Nikola Tesla, the protégé of Thomas Edison, was a remarkable scientist who improved the science of mechanical and electrical engineering diligently up until his death, where he began to be forgotten by those who study electrical and mechanical engineering. He invented many things, including the induction motor and the AC current. Tesla was known by many journalists and media as the stereotypical “mad scientist” up until his death in 1946.
This involves relating the current supplied to the motor, motor shaft rotational speed, motor efficiency, and the power factor as a function of the load of the motor, similar to the figure on page 21 of the Lab Manual.
The force that that turns the armature comes from the magnetic field of the armature trying to line up with the external magnetic field of the stator. This force is called torque. This torque will cause the armature to turn until its magnetic field is aligned with the external field, but no further. How does the armature continue to spin? One of the magnetic fields must be changed so that the armature has to turn again. The armature will spin so long as there is always a torque acting on it. How this is accomplished is what sets each type of electric motor apart.
Energy efficient motors use more copper and iron than regular motors. They also consume less energy than regular motors.
v+Vmaxsin(angular position of coil)”(cookeadamsdellmoore pg 509). This hopefully adds some insight into the use of electric motors, and the principles that make these motors work. Such as electromagnetism, binary switches for DC motors, and the selection of a running frequency of a motor through the use of an oscillator.
In this paper, I will talk about how AC circuits can be described by considering voltage and current using complex numbers. An AC circuit requires two separate numbers to be able to completely describe it. This is because it takes into account the amplitude and the phase of the current. The fact that complex numbers can be easily added, subtracted, multiplied or divided with each other makes them ideal for this operation where both amplitude and phase have to work together.
Not at all like an induction engine, the synchronous engine is energized by an outer DC source and, consequently, requires slip rings and brushes to give current to the rotor.
All useful generators of electricity come in two basic forms, alternating current and direct current. Direct current (dc) comes from generators that do not change in polarity, always producing a positive charge. In alternating current (ac) the polarity of the terminals is always changing from positive to negative. Thus you are left with alternating current flow. There are different ways of measuring and generating alternating and direct current.
Father of Alternating Current and AC induction motors, Nikola Tesla is known best for the high voltage generator that bears his name- the Tesla Coil. But this limited recognition hardly does justice to his legacy as an inventor. His name should be placed besides Thomas Edison, perhaps his biggest rival, for his contributions to electronics. But while electromagnetism was Tesla's primary focus during his life, the scope of his work and ideas were not so limited. He had many strange inventions and discoveries, many of which where not realized because of his opponents or for personal reasons. Others, as we will see, were simply too far-fetched or ambitious.
The stator is the stationary component while the rotor is the rotational component of the motor. Usually magnetic fields are created when an electric current is applied to a set of conductive wires wound together (Dixon, 2001). Magnetic fields can also be created using Permanent Magnets (PM). Electrical motors can also work as electrical generators (Correla, 1986). Electrical generators are devices capable of converting mechanical energy into electrical energy. An example would be a wind turbine which works as an electrical generator. It converts the mechanical energy of the rotating shaft caused by wind into electrical energy (Correla, 1986). The focus of this research will ...
As I uttered these inspiring words the idea came like a flash of lightning and in an instant the truth was revealed. I drew with a stick on the sand the diagram shown six years later in my address before the American Institute of Electrical Engineers”-Nikola Tesla . In 1882 Tesla went to work at Continental Edison Company in Paris. While there he made his first induction motor (or A.C. power) ,which made his boss, Charles Bachelor notice him as an inventor. After Charles started to noticed Tesla as an inventor, he sent him to the United States to work at another one of Edison's companies.