Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 6 Articles
DC brushless motors are widely adopted for their simplicity of control, even in sensorless configuration, and their high torque\r\ndensity. On the other hand, induction motors are very economical due to the absence of permanent magnets; for the same reason\r\nthey can easily be driven in the flux-weakening region to attain a wide speed range. Nevertheless, high dynamic induction motors\r\ndrives, based on field-oriented (FOC) or predictive control, require large amounts of computing power and are rather sensitive to\r\nmotor parameter variations. This paper presents a simple DTC induction motor control algorithm based on a well-known BLDC\r\ncontrol technique, which allows to realize a high dynamic induction motor speed control with wide speed range. The firmware\r\nimplementation is very compact and occupies a low amount of program memory, comparable to volt-per-Hertz- (V/f-) based\r\ncontrol algorithms. The novel control algorithm presents also good performance and low current ripple and can be implemented\r\non a low-cost motion control DSP without resorting to high-frequency PWM....
The paper presents and discusses an algorithm for average modeling of the PWM modulator in switch-mode power systems by\r\ngeneral purpose electronic circuit simulators such as PSPICE. A comparison with previous theoretical models is conducted. To test\r\nthe accuracy of the average PWM models comparison to cycle-by-cycle simulation was conducted. The proposed algorithm shows\r\nbetter accuracy than earlier counterparts...
An all-electric driveline based on a double wound flywheel, connected in series between main energy storage and a wheel motor, is\r\npresented. The flywheel works as a power buffer, allowing the battery to deliver optimized power. It also separates electrically the\r\nsystem in two sides, with the battery connected to the low voltage side and the wheel motor connected to the high voltage side. This\r\npaper presents the implementation and control of the AC/DC/AC converter, used to connect the flywheel high voltage windings\r\nto the wheel motor. The converter general operation and the adopted control strategy are discussed. The implementation of the\r\nAC/DC/AC converter has been described from a practical perspective. Results from experimental tests performed in the full-system\r\nprototype are presented. The prototype system is running with satisfactory stability during acceleration mode. Good efficiency and\r\nunity power factor could be achieved, based on vector control and space vector modulation...
Most of the failures of induction motors become insulation faults, causing a permanent damage. Using differential current\r\ntransformers, a system capable of insulation fault detection was developed, based on the differential relay protection scheme. Both\r\nsignal injection and fault detection circuitry were integrated in a single chip. The proposed scheme is faster than other existing\r\nprotection and not restricted to protect induction motors, but several other devices (such as IGBTs) and systems. This paper\r\nexplains the principle of operation of fault protection scheme and analyzes an integrated implementation through simulations\r\nand experimental results. A power-integrated circuit (PIC) implementation is presented....
In this brief paper, the dependency of short-circuit power on threshold voltage is\r\nanalyzed and utilized for short circuit (SC) power reduction in multi-threshold (MTCMOS)\r\nprocesses. Analytical expressions are developed for estimation of the change of ratio\r\nbetween short-circuit power and dynamic power (PSC/Pdyn) while changing the design\r\nprocess. The analysis shows that the PSC/Pdyn ratio can increase significantly if the VT/Vdd\r\nratio in new process decreases. An analytical expression is also derived for estimation of\r\npotential SC power reduction in MTCMOS processes by replacing low-VT transistors by\r\nhigh-VT devices in the same process. The proposed technique allows significant reduction\r\nof SC power without the need for process shift. The simulation results show good\r\ncorrelation with the analytical estimation at cell level, while demonstrating an average SC\r\npower saving of 36%. The performance impact is also validated, showing that timing\r\ndegradation is minor and controllable. The proposed optimization technique is applicable\r\nto any multi-threshold process. The technique is simple for implementation, and can be\r\neasily integrated in the existing optimization tools....
The unique properties of SiC devices enable substantial improvement of existing power conversion systems. SiC devices offer lower\r\nconduction and switching losses which increases converter efficiency.With high switching speed ability, employing SiC is expected\r\nto reduce weight and cost of conversion systems. This paper investigates the potential impact of SiC devices on renewable energy\r\napplications....
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