EPE Association: EPE 1985 - 20 - Lecture Session 3.06: DOUBLE-FED INDUCTION MOTOR DRIVES

EPE 1985 - 20 - Lecture Session 3.06: DOUBLE-FED INDUCTION MOTOR DRIVES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 20 - Lecture Session 3.06: DOUBLE-FED INDUCTION MOTOR DRIVES

   [return to parent folder]

   ACCURATE PREDICTION OF STEADY STATE PERFORMANCE OF SLIP-POWER RECOVERY VARIABLE SPEED DRIVE
By S. R. Alwash; R. Sh. Al-Ani; N. A. H. Issa [View]
[Download]

Abstract: An accurate method for predicting the steady state performance of slip power recovery system is presented. The method is based on modifying the already known d.c. and a.c. equivalent circuits of the system to take into consideration the effect of commutation overlap of the diode bridge. A simple iterative procedure is then used to solve the system equations because of the interdependence of the system parameters. A prototype has been assembled with the necessary hardware to operate the system at different inverter firing angles. Comparison of the experimental results and those calculated from the existing and the modified d.c. and a.c.equivalent circuits proved that accurate prediction of the system performance necessitate considering the commutation overlap. Furthermore, the effect of the motor resistance on the commutation process and thus on the system performance has proved to be of an important value particularly at low slips.

   DIGITAL SIMULATION OF DOUBLE-FED ASYNCHRONOUS MACHINE WITH CURRENT SOURCE INVERTER FOR MICROPROCESSOR CONTROL
By I. F. El-Sayed; P. K. Sattler [View]
[Download]

Abstract: Improvement in microprocessor technology will make possible further reduction of the hardware required and create additional options such as self-adaptive control. From the various possibilities to realize a variable-speed drive by combining a static converter and a polyphase ac machine, the double-fed asynchronous machine together with the current-source inverter offers a new and interesting drive system. An overall digital simulation of the complete converter-fed machine including the control system and the coupled machinery is proyided. This presents a treatment of the physical phenomena within the converter and the machine-converter interactions. This paper realizes such a simulation tool which will facilitate the study of a wide variety of transient as well as steady-state closed loop systems. The present system equations are derived on the basis of space phasors. The work has concentrated mainly on the prediction of system behavior and the development of control strategies for use in controlling ac machines with microprocessor. Several computer runs are shown to illustrate the simulation of typical inverter operation with the double-fed machine. Hence a simple observer model is developed to obtain the position of the rotor current space phasor and the rotor mechanical speed only by means of the electrical quantities. The control of the electromagnetic torque and the minimization of the pulsating torque are studied.

   ANALYSIS OF AN INDUCTION MOTOR WITH CONVERTER CASCADE IN THE ROTOR CIRCUIT
By V. Subrahmanyam; K. Surendran [View]
[Download]

Abstract: A mathematical model of an induction motor in the rotor frame of two of the three phases is used to simulate the behaviour of the motor having a converter cascade in the rotor circuit. Following an analysis of the commutation process of the machine side converter an expression is developed for the variation of current during commutation. A digital computer simulation is developed for the solution of these equations to obtain the performance of the motor. The rotor current waveform has been found to depend on slip frequency. The stator current is essentially sinusoidal superimposed by slip dependent harmonics. The torque developed has pulsations predominantly of six times rotor frequency.

   A RESEARCH OF NEW SCHERBIUS SYSTEM WITH HIGH POWER FACTOR
By T. Jinxian [View]
[Download]

Abstract: In this paper a theoretical analysis of commercial use of the Scherbius (cascade) system and a new idea to improve the power factor are given. It is shown that the speed-torque characteristics of the Scherbius system in various speed slip states can be represented by a simple formula. The maximum torque of that system is less than them maximum torque in proper operation, but it remains constant while the speed is regulated. The power factor of the common Scherbius system is very low (about 0.5 to 0.6). In order to increase it the author and co-workers have developed a new system which is based on the use of a forced commutation converter. The vector diagram and calculating formula are given. The power factor of this new system may reach 0.9 and even exceed it. Three industrial devices of this type have been operating in three factories. The largest device is a 245 KW motor which has a speed regulating domain of 40%. The experimental results are also shown in the paper. In one year an amount of 110 KWH electro-energy is saved by increasing the power factor. Compared to the use of the slip-difference machine, the use of the new system saves 440 KWH electro-energy in one year. The control of this new system is as simple as that of the common Scherbius system.

EPE 1985 - 20 - Lecture Session 3.06: DOUBLE-FED INDUCTION MOTOR DRIVES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 20 - Lecture Session 3.06: DOUBLE-FED INDUCTION MOTOR DRIVES
	[return to parent folder]

	ACCURATE PREDICTION OF STEADY STATE PERFORMANCE OF SLIP-POWER RECOVERY VARIABLE SPEED DRIVE By S. R. Alwash; R. Sh. Al-Ani; N. A. H. Issa	[View] [Download]
Abstract: An accurate method for predicting the steady state performance of slip power recovery system is presented. The method is based on modifying the already known d.c. and a.c. equivalent circuits of the system to take into consideration the effect of commutation overlap of the diode bridge. A simple iterative procedure is then used to solve the system equations because of the interdependence of the system parameters. A prototype has been assembled with the necessary hardware to operate the system at different inverter firing angles. Comparison of the experimental results and those calculated from the existing and the modified d.c. and a.c.equivalent circuits proved that accurate prediction of the system performance necessitate considering the commutation overlap. Furthermore, the effect of the motor resistance on the commutation process and thus on the system performance has proved to be of an important value particularly at low slips.

	DIGITAL SIMULATION OF DOUBLE-FED ASYNCHRONOUS MACHINE WITH CURRENT SOURCE INVERTER FOR MICROPROCESSOR CONTROL By I. F. El-Sayed; P. K. Sattler	[View] [Download]
Abstract: Improvement in microprocessor technology will make possible further reduction of the hardware required and create additional options such as self-adaptive control. From the various possibilities to realize a variable-speed drive by combining a static converter and a polyphase ac machine, the double-fed asynchronous machine together with the current-source inverter offers a new and interesting drive system. An overall digital simulation of the complete converter-fed machine including the control system and the coupled machinery is proyided. This presents a treatment of the physical phenomena within the converter and the machine-converter interactions. This paper realizes such a simulation tool which will facilitate the study of a wide variety of transient as well as steady-state closed loop systems. The present system equations are derived on the basis of space phasors. The work has concentrated mainly on the prediction of system behavior and the development of control strategies for use in controlling ac machines with microprocessor. Several computer runs are shown to illustrate the simulation of typical inverter operation with the double-fed machine. Hence a simple observer model is developed to obtain the position of the rotor current space phasor and the rotor mechanical speed only by means of the electrical quantities. The control of the electromagnetic torque and the minimization of the pulsating torque are studied.

	ANALYSIS OF AN INDUCTION MOTOR WITH CONVERTER CASCADE IN THE ROTOR CIRCUIT By V. Subrahmanyam; K. Surendran	[View] [Download]
Abstract: A mathematical model of an induction motor in the rotor frame of two of the three phases is used to simulate the behaviour of the motor having a converter cascade in the rotor circuit. Following an analysis of the commutation process of the machine side converter an expression is developed for the variation of current during commutation. A digital computer simulation is developed for the solution of these equations to obtain the performance of the motor. The rotor current waveform has been found to depend on slip frequency. The stator current is essentially sinusoidal superimposed by slip dependent harmonics. The torque developed has pulsations predominantly of six times rotor frequency.

	A RESEARCH OF NEW SCHERBIUS SYSTEM WITH HIGH POWER FACTOR By T. Jinxian	[View] [Download]
Abstract: In this paper a theoretical analysis of commercial use of the Scherbius (cascade) system and a new idea to improve the power factor are given. It is shown that the speed-torque characteristics of the Scherbius system in various speed slip states can be represented by a simple formula. The maximum torque of that system is less than them maximum torque in proper operation, but it remains constant while the speed is regulated. The power factor of the common Scherbius system is very low (about 0.5 to 0.6). In order to increase it the author and co-workers have developed a new system which is based on the use of a forced commutation converter. The vector diagram and calculating formula are given. The power factor of this new system may reach 0.9 and even exceed it. Three industrial devices of this type have been operating in three factories. The largest device is a 245 KW motor which has a speed regulating domain of 40%. The experimental results are also shown in the paper. In one year an amount of 110 KWH electro-energy is saved by increasing the power factor. Compared to the use of the slip-difference machine, the use of the new system saves 440 KWH electro-energy in one year. The control of this new system is as simple as that of the common Scherbius system.