Control electric generator machine motor system thesis

Control electric generator machine motor system thesis

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Home control electric generator machine motor system thesis

Motor controller

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A servo may be controlled using pulse-width modulation PWM.

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Switched reluctance motor

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Current control is particularly important for induction motors to protect the motor from excessive start up currents. Brushless DC motors are powered by a pulsed DC supply to create a rotating field and the speed is synchronous with the frequency of the rotating field.

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Battery and Energy Technologies

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The electronic circuits in the motor controller must be able to handle the full motor slectric and this may be a limiting factor in the design of a drive train.

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A much more stable system can be found by using the following "quadrature" sequence.

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In electrical circuits the delay may be associated with the inductive elements in the circuit which reduce the possible rate sysyem current build up in the circuit when a voltage is applied. Pulses may be magnetic or optical.

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The waveforms for traction applications are often stepped waves rather than pure sinusoids since they are easier to generate and the motor itself smoothes out the wave. The simplest case is a switch to connect a motor to a power source, such as in small appliances or power tools.

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If the supply voltage is reduced at light load levels, the air gap flux will be reduced accordingly and the current and slip will have to increase to produce the same torque. It is used in so called "Predictive Controllers".

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Controlling the dynamics of the machine and its response to applied loads.

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Time - Microprocessor clock. An adjustable-speed drive ASD or variable-speed drive VSD is an interconnected combination of equipment that provides a means of driving and adjusting the operating speed of a systm load.

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This is the same principle as used in light dimmer switches. These are therefore often called "sensorless" control methods.

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This method of power factor control is only practical for lightly loaded machines. The control systems outlined above are also designed to ensure that the electrical machine does not exceed its design voltage and current limits.

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Alternator Electric generator Inchworm motor.

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The position error deviation from 90 degrees is a measure of the required torque producing component of the stator current. The effect is to increase the load current with respect to the magnetising current, reducing the current lag and increasing the power factor.

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In many motor applications the generstor current may lag the supply voltage due to the inductance in the circuit and it is often desirable to control the current directly, rather than the voltage, to obtain more precise or faster control of the current and hence the torque. See AC motor speed control.

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This is commonly implemented with encoders, resolvers, and Hall effect sensors to directly measure the rotor 's position. Their purpose is to provide a current bypass path around the transistor to protect it from the dissipation of the stored energy in the inductive load the motor when the transistor is switched off.

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This page was last edited on 6 Februaryat Note - This is essentially a theis control system since the tachogenerator usually provides a DC voltage output which is compared with a reference input voltage.

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Systemm motors are usually employed when accurate position control is required. Voltage Choppers Modern controllers use switching regulators or chopper circuits to provide a variable DC voltage from a fixed DC supply.

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In practical terms, a system with high electrical or mechanical inertia will have a slow response long delay. The Ward Leonard speed controller provides a variable speed drive from the fixed voltage and frequency AC mains electric supply.

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Centrifugal switch Limit switch.

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Current control is particularly important for induction motors to protect the motor from excessive start up currents.

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Rather than using a troublesome high-maintenance mechanical commutator machinne switch the winding current as in traditional motors, the switched-reluctance motor uses an electronic position sensor to determine the angle of the rotor shaft and solid state electronics to switch the stator windings, which also offers the opportunity for dynamic control of pulse timing and shaping.

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The transition between reduced and full voltage may be based on elapsed time, or triggered when a current sensor shows the motor current has begun to reduce.

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Ward Leonard controllers can still be seen in passenger lifts elevators throughout the world as well as on electric cranes, winding gear in coal mines and industrial process machinery though they have now largely been superceded by thyristor speed controllers.

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This is an example of "Power Conditioning" whose purpose is to provide pure DC or sinewave power free from harmonics or interference. They can also include metering and communication functions.

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Current control systems outlined above are used to overcome this problem.

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Doubly-fed Linear Servomotor Stepper Traction. Many of the techniques involved in vector control are applicable to servo systems and consequently vector controlled system are replacing electruc of the traditional servo systems.

Similarly the voltage regulation of the on board generator and the regenerative braking charge pulses can also affect the battery adversely if not properly controlled.

Overload and over current protection may be omitted in very small motor controllers, which rely on the supplying circuit to have over current protection. Vector Control Summary Objectives Maximum current-to-torque power conversion, fast transient response, precise control of torque, speed and position. This requires a position sensor to feedback the angular position of the rotor shaft to the motor controller to enable it to switch the direction of the current when the rotor poles are in the correct position with respect to the stator poles.

This method of power factor control is only practical for lightly loaded machines. Closed Loop Systems Automatic Control Once the initial operating parameters have been set, an open loop system is not responsive to subsequent changes or disturbances in the system operating environment such as temperature and pressure, or to varying demands on the system such as power delivery or load conditions.

By varying the pulse width, the amplitude of the sine wave can be changed. Phase - Derived from time differences between measured and reference sources. To change the torque we need to change the in phase , torque producing, current but because we want the air gap flux to remain constant at its optimum level, the magnetising current should also remain unchanged when the torque changes. A microcontroller is also ideal for this kind of application since it enables a very precise control of the phase activation timings.

When power is applied to the stator windings, the rotor's magnetic reluctance creates a force that attempts to align the rotor pole with the nearest stator pole.

A larger motor requires a specialized switching unit called a motor starter or motor contactor. This is an example of "Power Conditioning" whose purpose is to provide pure DC or sinewave power free from harmonics or interference. Control systems for four quadrant applications will obviously be more complex than single quadrant controls. When too much current passes through the heating element for too long a time, the alloy melts and the spring releases the contact, opening the control circuit and shutting down the motor.

In practical terms, a system with high electrical or mechanical inertia will have a slow response long delay. The three phase sinusoidal input is fed to a simple diode full wave bridge rectifier block delivering a fixed voltage to the inverter.

Indirect - Sensorless Control Sensorless control only refers to the elimination of the position sensor used in the scheme above. Loop Gain The error signal is usually very small so the controlling circuit or mechanism must contain a high gain "error amplifier" to provide the controlling signal with the power to affect the change. For more precise control, vector controllers are used.

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