Showing papers on "Induction motor published in 1982"

Steady-state analysis of 3-phase cage motors with rotor-bar and end-ring faults

Abstract: An analysis is developed for 3-phase induction motors with any distribution and number of rotorbar and end-ring failures. The method is verified, using an inverted-geometry cage motor on which careful measurements of rotor-bar currents are made. The analysis is then used to investigate a rotor-bar fault on a 250 hp, 8-pole, 60 Hz motor.

Current Control of Voltage-Source Inverters for Fast Four-Quadrant Drive Performance

Abstract: A rotating reference frame controller for ac machines which enables smooth four-quadrant drive operation with good torgue control bandwidth is described. The advantages which result from the control of stator magnetomotive force (MMF) in a rotor reference frame are illustrated with regard to synchronous and induction motors. The application of this method to a cycloconverter synchronous motor drive is outlined.

Toroidally wound brushless DC motor

Abstract: A high speed DC brushless motor in which the stator is toroidal and the stator core does not include winding slots. In the preferred embodiment the core material for the stator is an amorphous metal alloy which provides high speed motor efficiency. For some applications core materials like ferrite or low silicon-alloys can be used. According to one embodiment of the invention a ferrite shielding ring can be added surrounding the motor to further improve high speed efficiency.

Motor control for a brushless DC motor

Abstract: This invention relates to a motor control system for a brushless DC motor having an inverter responsively coupled to the motor control system and in power transmitting relationship to the motor. The motor control system includes a motor rotor speed detecting unit that provides a pulsed waveform signal proportional to rotor speed. This pulsed waveform signal is delivered to the inverter to thereby cause an inverter fundamental current waveform output to the motor to be switched at a rate proportional to said rotor speed. In addition, the fundamental current waveform is also pulse width modulated at a rate proportional to the rotor speed. A fundamental current waveform phase advance circuit is controllingly coupled to the inverter. The phase advance circuit is coupled to receive the pulsed waveform signal from the motor rotor speed detecting unit and phase advance the pulsed waveform signal as a predetermined function of motor speed to thereby cause the fundamental current waveform to be advanced and thereby compensate for fundamental current waveform lag due to motor winding reactance which allows the motor to operate at higher speeds than the motor is rated while providing optimal torque and therefore increased efficiency.

Aircraft engine starting with synchronous ac generator

Abstract: The invention relates to a starter-generator machine (10) for starting turbine type aircraft engines. The machine combines an induction motor with a synchronous samarium cobalt generator. In the machine, a rotor-shaped stator (22) is fixed and positioned inside a squirrel-cage induction rotor (18) which has an array of samarium-cobalt magnets (24) attached on the outer diameter thereof. The compound dual machine operates as a starter by using the induction rotor to accelerate the permanent magnet rotor, and thus the aircraft engine via a drive pinion (34), up to some low synchronous speed, when ac power is applied to the outside stator (16) to lock in the permanent-magnet rotor (24) synchronously with the rotating field created in the stator (16) of the synchronous generator. As the speed of the rotor (24) is then increased, the engine speed is also increased via the drive pinion (34). In a second embodiment, a cartridge type induction-motor (70) is utilized to initially start an aircraft engine. The motor (70) includes a gear reduction (74) and a disconnect clutch (76) and drives the engine through a splined pinion (78) which in turn drives an engine connected spline (98). When the speed of the machine is such that the synchronous operation of an outside permanent magnet rotor (96) commences, the clutch (76) is utilized to disconnect the induction motor cartridge (70), leaving the rotor (96) to drive the drive spline (98) via internal splines (94).

Energy-Efficient Electric Motors: Selection and Application

Abstract: Induction motor characteristics energy-efficient motors electric power costs the power factor application of electric motors induction motors and adjustable-speed drive systems economics of energy-efficient motors and systems.

AC Motor-starting for aircraft engines using APU free turbine driven generators

Abstract: The invention is an electric starting system for starting aircraft jet engines (32), (34) and (36) using an APU (10) free turbine driven generator (12) The operating power factor of the starter-generator (12) is controlled during start mode operation of the APU (10) by monitoring the line current via a current transformer (58) Contactors (14) and (16) connect the generator (12) into the aircraft's ac power system and ac starting system, respectively A master start relay (22) is provided, and is closed in the `start` mode such that a power electronics inverter (24) may be powered from external power via contactors (18) The variable-voltage/variable-frequency output of inverter (24) is controlled via a logic controller (26) and can be applied sequentially to the three engine driven generators (32), (34) and (36) via start relays (42), (44) and (46) to start the engines (32), (34) and (36) respectively An alternative embodiment of the APU generator/power electronics/starter-generator start system is the utilization of a separate induction motor starter than can operate with or without the use of power electronics

Energy efficient ECS powered by a variable voltage/variable frequency power system

Abstract: The invention is an ECS system designed to utilize an induction motor (12) and a cabin compressor (14) for providing pressurized air that serves as a source of energy for heating, cooling, pressurizing and other air needs of modern aircraft. An aircraft engine driven generator, preferably a permanent-magnet generator (of the samarium-cobalt, SmCo, type), furnishes variable-voltage/variable frequency, VV/VF, power to the motor (12). The electric motor itself in the preferred embodiment is a highly reliable squirrel-cage induction motor (12) powered directly from the VV/VF supply, with the result that its speed is proportional to the generator frequency, which in turn is dependent on the aircraft engine speed. The main cabin compressor (14) and a secondary (auxiliary) supercharging compressor (18) are both mounted on the motor shaft. The motor-compressor configuration is further characterized in that the ac motor has pole-changing winding (typically two), which permits two speed operation, while the cabin compressor is provided with inlet guide vanes (16). The interactive combination of these two features makes it possible to furnish the requisite air mass flow and pressurization levels over the conditions of variable air density and variable atmospheric pressure, as the airplane operates throughout its flight envelope.

Analysis of Transient Electrical Torques and Shaft Torques in Induction Motors as a Result of Power Supply Disturbances

Abstract: A dynamic model for studying induction motor and power supply electromechanical interaction is presented. The electrical system is represented by conventional three-phase models. The motor-driven equipment shaft dynamics are determined by a lumped mass-torsional spring model. The electrical and torsional models are interconnected thru the motor electrical air gap torque and the speed and position of the motor rotor.

Inertial energy interchange system with energy makeup by combustion engine on demand

Abstract: Vehicle propulsion system or the like characterized by energy interchange between a plurality of flywheel assemblies each including a driving/driven induction motor/generator, and a plurality of vehicle drive wheel assemblies including drive wheels each directly driving/driven by an induction motor/generator, with energy makeup provided by a heat engine driven generator means, operated on demand, such energy interchange being by means of a multi-directional bus to which the flywheel and drive wheel motor/generators are selectively connected by variable frequency switch means and to which the engine driven generator is connected when operating, the switching being under control of a digital computer type controller, the controller receiving as inputs various vehicle operating conditions including flywheel, drive wheel, brake, steering angle and speed control positions, and bus voltage and heat engine driven generator operating condition, and the controller generating switch means controlling outputs causing energy transfer from or to the bus and to or from the drive wheel motor/generators to accelerate or decelerate the vehicle responsive to operator inputs, and causing energy transfer from or to the bus and to or from the flywheel motor/generators when the bus voltage is greater than or less than a predetermined value and to maintain the flywheels at substantially equal rotational speeds, and operating the heat engine and cause electrical energy transfer from the engine driven generator means to the bus whenever the total energy available from the motion of the vehicle and the kinetic energy of the flywheels is less than a predetermined value.

Induction motor control system

Abstract: Speed control of an induction motor is effected in digital fashion through use of a computer but without complex processing, and with a computer that need not be large in scale. This is accomplished by processing at least a speed command signal, actual speed signal and torque signal in analog fashion, enabling simplification of an induction motor speed control digital processing section which performs all other control operations in a digital manner. In a speed control network having a closed loop, a frequency-to-voltage converter, adder-subtractor, proportional integrator, polarity determining circuit absolute value circuit and voltage-to-frequency converter are constructed of circuitry operable on the basis of analog values, with all other circuits being constructed of circuitry operable on the basis of digital values.

Comparative Study of the Losses in Voltage and Current Source Inverter Fed Induction Motors

Abstract: The losses in an induction motor fed from six-step voltage and current source inverters are calculated and a comparison of efficiencies when supplied from these sources is given. The equivalent circuit that includes the effect of space harmonics and corrected for the skin effect in rotor bars is used for the calculation of main and stray copper losses. Stray iron losses due to magnetomotive force (MMF) and permeance harmonics, end leakage and skew leakage are also considered. Losses in the motor when supplied from these sources are also calculated using the modified equivalent circuit having stray and core loss resistors and their efficiencies are compared.

Brushless three phase direct current motor control circuit

Abstract: A driver circuit is coupled to the stator windings of a brushless three phase DC motor which is responsive to the open circuit back EMF voltage induced in the next stator winding to be energized as a permanent magnet rotor of the motor is caused to be rotated for producing phase current drive to the stator winding in synchronous with the operation of the motor. The driver circuit includes an increment drive circuit for supplying periodic switching command signals in succession to a switching circuit to produce phase current drive in each stator. The increment drive circuit increments a switch command signal to cause phase current through the next phase stator winding in reference to the magnitude of the EMF voltage induced across said phase stator winding falling below a reference level. A feature of the invention is that the frequency of the periodic switch command signals is varied during starting of the motor dependent on the magnitude of starting potential supplied to the driver circuit to prevent the motor from "locking" which would otherwise inhibit start thereof.

Phase advance waveform generator for brushless DC actuator system controller

Abstract: This invention relates to a motor control circuit for a permanent magnet motor having a rotor and motor windings. A motor winding transformer circuit is coupled to motor windings and provides an output signal representative of the magnitude and direction of the real current present in the motor windings. A rotor speed/position sensing circuit provides an output signal representative of the motor speed and direction.

A quantitative analysis of induction motor performance improvement by SCR voltage control

Abstract: Minimum input power and maximum efficiency operation occur at characteristic slip values which can be realized for any induction motor operating at part load by properly adjusting the amplitude of the applied stator terminal voltages. It is shown that these two criterion yield perceptibly different results when the motor is driven from an SCR voltage controller. In addition, it is demonstrated that a constant power factor controller results in an operating regime which is substantially poorer than operation at either minimum input power or maximum efficiency. It is further shown that minimum stator current and minimum power factor angle criterion yield results which are closer to the ideal than the constant power factor controller.

Third-order theory and bang-bang control of voice coil actuators

Abstract: A theory of voice coil motor actuators involving third-order differential terms in displacement that includes the inductance of the motor coil has been developed for bang-bang control time-optimal performance. Universal curves have been obtained using the theory that exhibits relationships between dimensionless quantities. The curves enable designers to choose appropriate actuator performance parameters to meet design objectives. Experimental methods have been described to determine some of the important parameters involved in the theory.

Microprocessor-based efficiency optimization control for an induction motor drive system

Abstract: A microcomputer for use with an induction motor drive system processes machine drive system currents, voltages and speed to compute real time machine efficiency. From real time machine efficiency determinations, the microcomputer determines the optimum combination of machine slip frequency and machine air gap flux. The magnitude and frequency of machine stator current are regulated, responsive to the difference in magnitude between optimum machine air gap flux and actual machine air gap flux, and the difference in magnitude between optimum slip frequency and actual slip frequency, respectively, to assure machine steady state operation at maximum efficiency irrespective of machine load conditions.

Method and apparatus for controlling AC motor

Abstract: A method and apparatus for controlling an induction motor, in which an AC power source is connected to the induction motor through a switch and a frequency converter, and the motor speed is controlled by controlling the output frequency and output voltage of the frequency converter. In the starting operation, the induction motor in a free-running state is supplied with an initial voltage in a given frequency which is expected to make the absolute value of the motor current minimum or near minimum, and then the supply voltage is increased gradually from the initial voltage with its frequency being retained at the given voltage. When the output frequency of the frequency converter reaches a predetermined value, the output frequency and voltage thereof are increased gradually with the ratio therebetween being maintained at a given value.

Multi-quadrant brushless DC motor drive

Abstract: A control circuit for a brushless DC motor providing positive control in all four quadrants of motor operation. The circuit provides control of motor current, thereby controlling motor torque, in response to an applied current command signal, relying solely on feedback signals of motor current and rotor angle. The heart of the system is a level dependent logic stage which selectively controls the states of the switches applying power to the motor windings in accordance with a current error signal developed by reference to the feedback current signal. The control circuit causes the motor current to correspond to any applied current command and works at any motor speed and torque for rotation in either direction. In a preferred embodiment, the basic control system is combined with additional feedback loops developing servo information regarding rate and actuator position to provide a overall position control system, such as is particularly useful in place of the hydraulic actuator systems now employed in aircraft.

Apparatus and method for determining the operation of an induction motor

Abstract: From the sensed input voltages and currents fed into a standard induction motor the stator resistance is known instantaneously through a direct and quadrature treatment of the sensed quantities from which are derived at least four of the following five quantities: the motor overall reactance, the motor overall real impedance, the air gap reactance, the parallel combination of stator and rotor leakage reactances and the stator leakage reactance. This derivation uses the motor intrinsic characteristics at rest, while those four quantities are used in ascertaining the stator resistance instantaneously and recurrently during motor operation, thus, without any sensing means on the motor itself. The load reactance is also determined with the above-stated five quantities. From the knowledge of the stator resistance and the load resistance, a simulated two-phase network is provided and used to ascertain any of the key process variables typically used in an induction motor drive, such as shaft speed, slip, flux, torque. The temperature and load of a standard induction motor are known without sensing and the motor can be remotely controlled for protection against overheating, or overload.

Calculating Short-Circuit Currents with Contributions from Induction Motors

Abstract: Chapter 7 of a forthcoming book, Recommended Methods for Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems (IEEE Violet Book) is discussed. The book will be one of the IEEE Standards Board ``Color Book'' series of Recommended Practices prepared by the Industrial Power Systems Department of the IEEE Industry Applications Society. (It is being developed under IEEE Project Authorization P551.) The chapter describes the nature of induction motor short-circuit current contributions, discusses calculating techniques, and examines the simplified methods of accounting for induction motor contributions described in ANSI C37 Circuit Breaker Standard Application Guides. An extension of these simplified methods is recommended to eliminate the possible need for duplication of calculations. Examples of calculations are included. For this chapter, it is assumed that other chapters in the ``IEEE Violet Book'' cover the purpose of short-circuit calculations, calculating methods available, and details of calculations involving passive power system components and synchronous machines.

Control system for AC induction motor

Abstract: A control system is disclosed for connecting the primary windings of a three-phase AC inducton motor in a delta-connection at heavy loads and for automatically reconnecting the windings in a wye-connection at light loads to effect energy savings. Power sensing means produces a control signal which is directly proportional to the power applied to the induction motor. Differential comparator means respond to the control signal and to an adjustable reference signal, representing a preselected power input level, for generating an actuating signal for switching a wye-delta starter between two conditions, one of which effects the wye connection and the other the delta connection. When the power input is below the preselected level the wye-connection is established, whereas the delta-connection is made when the power input is above the preselected level.

A New Approach to Dynamic Modeling and Transisent Analysis of SCR-Controlled Induction Motors

Abstract: A dynamic model based on instantaneous symmetrical components theory is presented for purposes of transient analysis of thyristor-controlled three-phase induction motors. The distinct advantages of this model over the phase-variable model have been highlighted. In-line switching constraints are incorporated and the simulation of all operating modes is accomplished without reference to rotor position. Typical transient response patterns are presented using the new model and comparisons are made with similar results obtained by earlier methods.

Apparatus for controlling high voltage by absorption of capacitive vars

Abstract: Apparatus for controlling high voltage by absorption of capacitive vars, comprising a stator (10) having a core and a three phase winding (14) connected to the high voltage, and a rotor (12) having magnetic material (20) exhibiting a sharp magnetic saturation. The rotor (12) includes longitudinally extending damper bars (22) imbedded in grooves or slots (24) in a manner similar to the bars used in a squirrel cage rotor. The magnetic structure of the rotor can be of two types--a symmetrical structure for asynchronous operation, and a salient pole structure for synchronous operation. In the case of the symmetrical rotor construction, the stator (10) and rotor (12) constitute a rotating induction reactor (8) which operates in the same manner as a free running, unloaded induction motor. The induction reactor (8) exhibits characteristics similar to a saturable reactor with respect to var versus voltage absorption, but does not have the undesirable harmonics normally present in the saturable reactor. In the case of the salient pole rotor construction the stator (10) and rotor (12) constitute a rotating synchronous reactor which operates in the same manner as a free running unloaded reluctance motor. A series compensation arrangement can be provided by connecting capacitance means (24,26,28) in series with the stator winding (14) to reduce the droop characteristic of the incremental saturated inductance of the reactor (8) to almost zero. The transformer connecting the rotating reactor to the high voltage system can be provided with amps for steady state adjustment of the voltage level to be controlled.

Current source inverter bed induction motor drive

Abstract: A drive system for a polyphase induction motor for extending the range of high frequency operation has two current source inverters connected to the polyphase motor to supply power to the motor. Motor speed and motor load are sensed and a circuit responsive to increasing motor speed and decreasing motor loads advances the firing pulses of one inverter while delaying the firing pulses of the other inverter. The advance in firing of one inverter and the delay in firing the other, reduces the effective current supplied to the motor while not decreasing the current available in each inverter for commutation.

General Rotating mmf Theory of Squirrel Cage Induction Machines with Non Uniform Air Gap and Several Non Sinusoidally Distributed Windings

Abstract: A new method is given to study the performances of squirrel cage motors of complex design (non uniform air gap, windings with high space harmonic content). It is based on the analysis of electric circuits with time varying coefficients, rather than on consideration of air gap fluxes. It is shown that this method provides good results. It is the basis of a companion paper devoted to the motor which has been the object of the 1975-1976 IEEE single phase motor calculation and test project.

Electric motor controls for mechanical actuators

Abstract: Methods and apparatus for controlling an electric motor effect operation of such motor by electric energization thereof, and derive from a motor winding or from the back electromotive force of the motor an electric signal indicative of motor speed. The motor is thereupon mechanically stalled, and such stalling is detected from a comparison of the derived speed signal and the electric energization. Deenergization of the motor is effected in response to the stalling detected from the latter comparison. Limit switching of electric motors and actuators without limit switches may be provided in this manner.

Self generative PWM voltage source inverter induction motor drive

Abstract: A PWM, controlled current, voltage source inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexer are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.

Control system for an induction motor with energy recovery

Abstract: A control circuit for an induction motor powered system wherein a power factor controlled servo loop is used to control, via the phase angle of firing of a triac (16), the power input to the motor (14) as a function of load placed on the motor (14) by machinery of the powered system. Then, upon application of torque by this machinery to the motor (14), which tends to overspeed the motor, the firing angle of the triac (16) is automatically set to a fixed, and relatively short, firing angle.

Prevention of harmonic torques in squirrel cage induction motors by means of soft ferrite magnetic wedges

Abstract: It is well known that the harmonic torques in squirrel cage induction motors are caused by the space harmonic waves in air-gap flux distribution. The soft ferrite magnetic wedges inserted into the stator slot openings reduce the ripple of air-gap permeance. Therefore, this wedges reduce the magnitude of harmonic torques. A trial was performed on prevention of harmonic torques in squirrel cage induction motors, by inserting a soft ferrite magnetic wedges into its stator slot openings. Results obtained were as follows; (1) The soft ferrite magnetic wedges made it possible to decrease by about 40% the 17th and 19th asynchronous torques. (2) The magnitude of 17th and 19th asynchronous torque on the induction motor with the soft ferrite magnetic wedges and the unskewed rotor is approximately equivalent to that on the induction motor with the rotor skewed through 0.4 stator slot pitch. (3) The soft ferrite magnetic wedges were incapable of decreasing the 5th asynchronous and synchronous torque. The authors suggest that the utilization of soft ferrite magnetic wedges will become important to prevent the harmonic torques in induction motors.