Kenzo Kamiyama

A Microprocessor-Controlled High-Accuracy Wide-Range Speed Regulator for Motor Drives

A new speed measurement system, which is suitable for microprocessor-based motor drive, and its application to speed regulator are explained.

A Microprocessor-Controlled Fast-Response Speed Regulator with Dual Mode Current Loop for DCM Drives

A new control method is described in which a microprocessor is used to regulate the speed of a dc motor driven by antiparallel-connected three-phase dual thyristor converters. A distinct feature of this speed regulating system is that speed response is improved by using a fast-response current controller for the internal loop. A fast-response current controller is obtained by employing a nonlinear compensation subloop and a proportional plus integral compensation subloop. The nonlinear compensation subloop is used to linearize the nonlinear load characteristics of the thyristor converter, which are encountered under discontinuous conduction states of current. The proportional plus integral compensation subloop reduces the deviation of detected current from the current reference. With these two current-control subloops a fast motor speed response is achieved under discontinuous as well as continuous conduction states; hence the steady-state accuracy of speed is improved. A speed regulator using a microprocessor was trial manufactured and tested with a 20-kW dc motor. It was found that an extremely fast controlled current response can be obtained even with a relatively long sampling period. Further, normal action was confirmed in four-quadrant operation.

A microprocessor-controlled speed regulator with instantaneous speed estimation for motor drives

A method for estimating instantaneous speed, suited for a microprocessor-based speed regulator for motor drives, and the characteristics of the speed control system are described. Features of the proposed method include the estimation of instantaneous speed at a real-time point using values of average speed detected by counting for a certain time the output pulses of an encoder as well as the estimated value as the speed feedback signal for the speed regulator. Since this method allows compensation to be made for the lag time of the feedback signal caused by detection of the mean value, it contributes to improved stability of the speed regulator. In particular, this provides a significant suppression of the vibrations that are generated in motor-driven machinery. >

A multiple PWM GTO line-side converter for unity power factor and reduced harmonics

A multiple PWM GTO line-side converter with low switched frequency has been developed for industrial uses needing both higher capacity and performance. The multiple converter is composed of two GTO converter units parallel connected through an interphase reactor. The switching frequency of the GTO thyristors in the multiple converter can be reduced to a quarter of that in the single converter. It is verified by simulations and experiments with a 2750 kVA GTO converter and inverter system with 500 Hz switching frequency that the system has: (1) a unity power factor, (2) reduced harmonics, (3) bidirectional power flow, and (4) speed regulatory performance equal to that of an advanced cycloconverter drive system.<<ETX>>

Quick response and low-distortion current control for multiple inverter-fed induction motor drives

This paper describes a PWM control method to balance two unit inverter currents and to reduce the distortion of motor currents in a multiple GTO inverter for large capacity AC variable-speed drive systems. For an 11 kW induction motor driven by a 15 kVA multiple inverter, the imbalance current can be reduced to less than 5% of the rated motor current, and the motor current waveform can be made very close to sinusoidal. The GTO switching frequency in the multiple inverter can be lowered to one-quarter of that in the single inverter. In a 2750 kVA GTO inverter drive system which was developed based on the 15 kVA multiple inverter, excellent performance is obtained including unity power factor operation at an AC power source, smooth 4-quadrant operation, and quick speed response of 85 rad/s. The quick response is realized by field-oriented control with decoupling control between torque and exciting currents, and direct control of three-phase AC currents. In the future, the multiple GTO inverter is expected to be applied to rolling mill drives instead of cycloconverters. >

A Fully Digitalized Speed Regulator using Multimicroprocessor System for Induction Motor Drives

A fully digitalized speed regulator is proposed which executes all regulatory processing by using a multimicroprocessor. The hardware configuration of the regulator is standardized. A vector control algorithm is used to perform fast response speed control of an induction motor. Microprocessors execute a PWM gate pulse generation and current component detection in addition to speed control processing. In applications of the regulator to a 1.5-kW induction motor drive system, Its effectiveness is confirmed.

A high accuracy current component detection method for fully digital, vector-controlled PWM VSI-fed AC drives

A high-accuracy differential-type current component detection method and test results are described. The method is suited for vector-controlled pulse width-modulated (PWM) VSI-fed adjustable-speed AC drives. Its features include elimination of high-frequency current harmonics and correction of the detection error caused by the lag time of time-sharing processing. Since this method allows current-loop calculations at a slower sampling rate with a conventional microprocessor, it realizes a fully digital speed regulator with a minor current component loop. Simulation results and experimental results are presented.<<ETX>>

A Multimicroprocessor-Based Fully Digital AC Drive System for Rolling Mills

Theoretical considerations are given for a control scheme to decrease voltage disturbances in a cycloconverter-fed ac drive system, using a form of the vector control concept. The theory has been applied to a multimicroprocessor-based fully digital 72-arm cycloconverter-fed 5000-kW squirrel-cage induction motor drive control system. For speed and position sensors, a high-resolution sine encoder which generates a 15 000-sine wave/r has been developed to achieve high-performance speed regulation, particularly at ultra-low speeds. The factory test results compare far more favorably than those attainable using dc drives. They reveal that the ac drive system is suited to practical applications in main drives for rolling mills, including tandem cold mills.

Application of Fully Digital Speed Regulators to Tandem Cold Mills

A fully digital speed regulator has been developed for industrial applications mainly in the steel industry. The benefits obtained when the digital speed regulator was used in two different tandem cold rolling mill control systems are described. As compared with conventional analog control, fully digital speed control permitted more stable rolling mill operation, reducing both threading and accelerating times by 50 and 27 percent, respectively, and leading to increased productivity. With the off-gauge length reduced by about 40 percent, the yield was improved accordingly. In addition, with the fully digital speed regulator which employs LSI devices having reduced failure rates, the tandem cold rolling mill control system was entirely computerized from supervisory process computers to motor drive regulators. With easier trouble-shooting capability, the system failure rate was decreased to 50 percent.

Analysis of Transient Firing Angle in Reversible Thyristor Drive Speed Regulator for Mill Motor

When designing a high-response thyristor-drive speed regulator with internal multicontrol loops for a rolling mill motor, the behavior of the transient firing angle must be taken into consideration to ensure consistent thyristor switching, which is often neglected, and to achieve the required dynamic performance. The critical conversion modes in which the minimum transient firing angles in rectification and inversion may appear in a dual thyristor converter for four-quadrant motor drives are clarified. Two methods of analyzing the transient firing angles in the critical conversion modes and the results of calculations of the minimum transient firing angles under specified operating conditions are also presented. The calculated results are verified in laboratory tests.