Kichiro Yamamoto

Characteristics of permanent-magnet synchronous motor driven by PWM inverter with voltage booster

The steady-state characteristics of an interior permanent-magnet (IPM) motor driven by a pulse-width-modulation (PWM) inverter with voltage booster are analyzed and the transient behavior is investigated. The PWM inverter with voltage booster consists of a conventional PWM inverter and a voltage booster to control the DC-link voltage. The current trajectory on the i/sub d/-i/sub q/ plane is illustrated and the torque, voltage, and current versus speed characteristics are represented. Furthermore, the analytical and simulated results are compared to the experimental results for a 1.5 kW IPM motor and the validity of the analysis and simulation is confirmed by their agreement.

A study of dead-time of PWM rectifier of voltage- source inverter without DC link components and its operating characteristics of induction motor

A voltage-source inverter without dc-link components is an ac-to-ac converter having dual bridges of a pulsewidth-modulated (PWM) rectifier and a PWM inverter that can be controlled independently. While conventional matrix converters have disadvantages, such as a complicated commutation scheme and necessity of a large-sized clamp circuit, commutation, and protection of our inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of a snubber circuit are described when a 0.75-kW induction motor is driven by our inverter.

Characteristics of permanent magnet synchronous motor driven by PWM inverter with voltage booster

The steady state characteristics of the interior permanent magnet (IPM) motor driven by the PWM inverter with voltage booster are analyzed and the transient behavior is investigated. The PWM inverter with voltage booster consists of a conventional PWM inverter and a voltage booster to control the DC link voltage. The current trajectory on the i/sub d/-i/sub q/ plane is illustrated and the torque, voltage and current versus speed characteristics are represented. Furthermore, the analytical and simulated results are compared to the experimental results for 1.5 kW IPM motor and the validity or the analysis and simulation is confirmed by their agreement.

Comparison between flux weakening and PWM inverter with voltage booster for permanent magnet synchronous motor drive

The operation by the PWM inverter with voltage booster is compared with the flux weakening operation for 1.5 kW interior permanent magnet synchronous motor drives. Equations are derived and performances are analyzed for both operations. Current trajectories in the i/sub d/-i/sub q/ plane are shown. In addition, torque, voltage, current and efficiency versus speed characteristics, which are obtained from analysis for both operations, are compared. The results show some advantages of the operation by the PWM inverter with voltage booster.

Effect of parasitic capacitance of power device on output voltage deviation during switching dead-time in voltage-fed PWM inverter

The PWM inverter, which is operated at a high carrier frequency, is influenced by the switching dead-time. In this paper, the effect of the parasitic capacitance of the power device on the voltage deviation during switching dead-time is investigated and a numerical method to analyze the output voltage deviation in consideration of the parasitic capacitance of the power device is proposed. Furthermore, this method is applied to a permanent-magnet AC servo motor drive system and the voltage deviation and the phase current waveforms are calculated. Finally, the calculated results are compared with the experimental results in order to confirm the validity of the analysis.

Influence of motor rotating speed on shaft voltage of brushless DC motor with insulated rotor driven by PWM inverters

The brushless DC motors are also becoming popular in air conditioning fan motors, and protection of bearing from electro-erosion is becoming a major challenge in the North Europe market in particular. The bearing electro-erosion is caused when the bearing lubricant is dielectrically broken down, making current run on the inner race and outer race of the bearing. As a countermeasure, we verified that shaft voltage was suppressed by the insulated rotor. Air conditioning fan motors are known to generate the necessary wind for cooling the heat exchanger and its motor rotating speed. It was also confirmed that the shaft voltage increased as the motor rotating speed increased. This paper describes the shaft voltage falls below the dielectric breakdown voltage of the bearing grease in the actual operating speed range and is also verified that insulated rotors are effective for suppressing electro-erosion with respect to changes in rotating speed.

Comparing Brushless DC Motors: A Method of Suppressing the Shaft Voltage Even in a Grounded Motor Frame

The voltage-source pulsewidth modulation (PWM) inverter generally used to drive air-conditioning fans has posed a major problem, i.e., the high probability of electrical erosion of the bearing. Through inverter switching, a potential difference called the shaft voltage is generated between the inner and outer races, causing an electrical breakdown of the bearing lubricant. This results in a current, sometimes called the electric discharge machining current, passing through the bearing, which causes bearing erosion. The shaft voltage is reduced by the use of an insulator inserted between the outer and inner cores of the rotor in an air-conditioning fan motor where the frame is not grounded. This article describes the calculated and measured waveforms of the shaft voltage for the insulated rotor brushless dc (BLdc) motor driven by a PWM inverter. The insulated rotor also has the effect of suppressing the shaft voltage even when the motor frame is grounded.

Investigation of calculation method of losses in PWM inverter with voltage booster using both DC link voltage Control and flux weakening control

In this paper, authors investigate calculation method of losses in system which consists of interior permanent magnet (IPM) motor and PWM inverter with voltage booster. This system has two driving methods for motor in high speed region. One is DC link voltage Control. The other is flux weakening control. However, it is not cleared how combination of these two control methods is suitable for this system. It is necessary to quantitatively estimate parts of system losses in voltage booster, inverter and IPM motor, because total efficiency of system is decided by parts of system losses. So, the simulation model, which is capable of calculating parts of system losses to find suitable driving method for IPM motor using combination of the two control methods, is introduced and simulation results are discussed.

Study of the Further Reduction of Shaft Voltage of Brushless DC Motor With Insulated Rotor Driven by PWM Inverter

Authors succeeded in reduction of the shaft voltage of a motor with an insulated rotor driven by PWM inverter previously. This paper proposes a new method of further reduction of the shaft voltage of the motor with the insulated rotor. A non-grounding common-mode equivalent circuit of the motor is examined, and the effect of the further reduction by a new method is verified by calculation of the shaft voltage from the equivalent circuit and measurement of the shaft voltage of the motor.

Steady State Characteristics of PWM Inverter with Voltage Boosters for Permanent Magnet Synchronous Motor Drives

Steady state characteristics of an interior permanent magnet (IPM) motor drive system, which has regenerating circuit of double-layer capacitors, are investigated by simulation. In the system, two voltage boosters are equipped and the double-layer capacitors are arranged in series with battery to reduce the number of capacitors. A strategy to control the power flow of the system and also a strategy of battery current indirect control are indicated. Furthermore, proposed system is investigated for 1.5kW IPM motor drive by simulation and the validity of the strategies is demonstrated. Finally, the relation between the currents of voltage boosters and the ratio of battery voltage to voltage of double-layer capacitors is discussed.