Tadayuki Kitahara

Improved Performance of Induction Motor Using Magnetic Energy Recovery Switch

This paper discusses applications of a magnetic energy recovery switch (MERS) to induction motor drive. The MERS is a series compensation device, which can control voltage and input power factor. Characteristics and operation principles of voltage control and power factor correction by MERS are described. Some applications of the MERS to induction motor drive are investigated. Series capacitor compensation may cause some unstable situation. Electrical oscillations caused by the self-excitation with series capacitor are discussed. Experimental results show the MERS also can cause the same problems since the MERS works as a series capacitor. A 5.5 kW experimental system was developed. Damping control by terminal voltage feedback is investigated. Experimental results show that damping control is effective for improving stability of the induction motor drive with MERS. Starting and steady state characteristics are evaluated experimentally.

Series Connected Power Flow Control using Magnetic Energy Recovery Switch (MERS)

A new series connected power flow controller, called the magnetic energy recovery switch, has been investigated. It is characterized by four active switches and a dc-capacitor in each phase. The device is capable of injecting up to rated voltage within the current rating. It behaves similar to a controllable voltage source and a variable capacitor connected in series. A control algorithm has been developed in order to facilitate power flow control with these combined characteristics. Experimental results suggest the MERS to be a promising new power flow controller.

Control of series compensated induction motor using magnetic energy recovery switch

This paper proposes a induction motor drive using magnetic energy recovery switch (MERS). The MERS is a series compensation device and it can control the load voltage and input power factor. Stability problem because of self-excitation was found. However, this could be solved with voltage feedback control. Small scale experiments and field test results are reported.

Variable frequency induction heating using magnetic energy recovery switch (MERS)

This paper proposes a power converter for induction heating which can control the output frequency. This power converter is using a configuration named MERS (magnetic energy recovery switch). A 90 kVA 150-1000 Hz controllable frequency power supply for steel strip induction heating was developed. The power supply used optimally designed IGBTs for the MERS configuration. Loss reduction due to soft-switching and use of the IGBTs makes induction heating possible to operate with variable frequency. Demonstration using the proposed power supply confirms advantages of variable frequency operation.

Improvement of Synchronous Generator Charateristics Using Bi-directional Current Phase Control Switch

This paper has suggested a new configuration for reducing the excitation need of synchronous generators. The configuration consists of a synchronous generator connected in series with a bi-directional current switch. The switch injects a series voltage which cancels the synchronous reactance of the generator. The series voltage is automatically generated by absorbing the magnetic energy stored in the synchronous reactance. The excitation level reduction has been verified with experimental results for an island grid. The low change in excitation for various loads also indicates that this concept can be used with constant excited generators, also permanent magnet generators