Shaft Voltage Reduction Research Articles

Analysis, Calculation and Reduction of Shaft Voltage in Induction Generators

This paper presents analysis of shaft voltage in different configurations of a Doubly Fed Induction Generator (DFIG) and an Induction Generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems are investigated on shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied with mathematical analysis and simulations.

Reduction of Shaft Voltage of IPMSM According to the Shape of the Novel Shield Ring

Reduction of Shaft Voltage of IPMSM According to the Shape of the Novel Shield Ring

Verification of Shaft Voltage Reduction Effect Using Layered-Shield in EV Traction Motors

Verification of Shaft Voltage Reduction Effect Using Layered-Shield in EV Traction Motors

Proposing the New Layered-Shield Structure for Shaft Voltage Reduction in IPMSM

Proposing the New Layered-Shield Structure for Shaft Voltage Reduction in IPMSM

Application of Perovskite Layer to Rotor for Enhanced Stator-Rotor Capacitance for PMSM Shaft Voltage Reduction

Adjustable speed drives use Pulse Width Modulation (PWM) to switch DC-bus voltage for the synthesis of three-phase voltages to provide power to the permanent magnet synchronous motor (PMSM). This switching action produces very short rise and fall times and Common Mode Voltage (CMV) in the motor winding, exciting the parasitic capacitances inherent to the motor geometry. These parasitic capacitances give rise to shaft voltage due to a voltage divider action. Therefore, in this paper, first, motor parasitic capacitances and voltage divider action is explained. Second, the Barium Titanate (BTO) layer is coated onto the rotor to enhance stator-to-rotor compound capacitance and a simulation is performed showing the dependence of the shaft voltage on the permittivity of the perovskite (BTO) layer. The rotor BTO layer reduces the bearing voltage ratio as well. Third, experimental results are presented showing effectiveness of the application of the BTO layer to rotor and reduction of shaft voltage of the motor in anticipation to mitigate the damaging electric discharge machining (EDM) bearing currents. Likewise, the experiment shows that the magnetic design of the motor is not affected by the BTO layer to rotor.

축 전압 저감 구조 모터의 축 전압 주파수 응답 특성 분석

In PWM based inverter driven motor, shaft voltages usually cause bearing fault. Many methods to mitigate the shaft voltages have been proposed. Since the high frequency components are hazardous to bearing, it is necessary to analyze the frequency responses for each shaft voltage mitigation method. In this paper, frequency responses of three shaft voltage mitigation methods are analyzed and compared. First, equivalent circuit models regarding geometric shape of motor are presented. Second, modified models of each equivalent circuit containing shaft voltage reduction methods are proposed. Finally, the comparison of the frequency responses for each shaft voltage mitigation method is presented.

Mitigation Method of the Shaft Voltage According to Parasitic Capacitance of the PMSM

This study proposes the shaft voltage mitigation method according to change in parasitic capacitances of a permanent magnet synchronous motor. To consider the shaft voltage reduction in the initial motor design process without any filter, the parasitic capacitances affecting the shaft voltage are calculated using the motor geometry parameters. Then, the shaft voltage is analyzed according to change in parasitic capacitances using the equivalent circuit model and the torque characteristic is also analyzed to effectively mitigate the shaft voltage. As a result, the rotor-to-winding is determined as an appropriate parameter to mitigate the shaft voltage among the parasitic capacitances, because it affects the shaft voltage and does not affect the output torque. Finally, the shaft voltage mitigation method according to variation of rotor-to-winding capacitance is verified by experiment.

Turboset shaft voltage

The paper presents an analyses of shaft voltage and bearing current phenomena in electrical machines. An overview of the causes of these voltages and currents and their possible consequences is also given. The influence of the thyristor excitation system on the level of shaft voltages is examined, followed by the proposal of a measuring method and the preventive measures for shaft voltage reduction. Finally the paper reports the experimental measurements of shaft voltages on a turbo set that is a part of the Electric Power Industry of Serbia.

Bearing Currents and Shaft Voltage Reduction in Dual-Inverter-Fed Open-End Winding Induction Motor With Reduced CMV PWM Methods

Exploiting the rich switching redundancies of the dual inverter, new hybrid pulsewidth-modulation (PWM) switching methods are proposed in this paper using the degree of freedom of operating the individual inverters independently, in addition to exercising the degree of freedom of controlling the switching action of the individual legs independently. Two voltage entities, namely, common-mode voltage (CMV) and differential-mode voltage are identified in the dual inverter, and all hybrid PWMs are envisaged aimed at reducing and also eliminating the CMV in it. The effects of such attempts on motor shaft voltage and also the motor bearing currents are presented in detail. Furthermore, bearing current profiles of an open-end winding induction motor are also presented with both conventional and hybrid PWMs proposed in this paper. Electric discharge machining discharge currents are completely eliminated with the use of all hybrid PWM methods proposed in this paper. In addition, implications of completely eliminating the CMV are also presented in this paper. All hybrid PWMs proposed in this paper are first simulated using MATLAB and are experimentally verified on a dual two-level inverter feeding a 1.1-kW 415-V 3-φ open-end winding induction motor drive.

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

The authors previously succeeded in reducing the shaft voltage of a PWM driven motor with a rotor which had an outer core and an inner core (and the shaft), electrically insulated each other by a resin (hereafter, the insulated rotor). This paper proposes a new method for further reduction of the shaft voltage of a motor with an insulated rotor by adding a capacitor between brackets and N line of the dc link of the inverter. A common-mode equivalent circuit of the system with an ungrounded motor is examined, and the effect of further reduction by the new method is verified by calculation of the shaft voltage from the equivalent circuit and measurement of the shaft voltage of the motor.

Optimization of Magnetic Flux-path Design for Reduction of Shaft Voltage in IPM-Type BLDC Motor

In this paper, we propose a method for suppressing shaft voltage by modifying the rotor shape and the permanent magnets in interior permanent magnet type high voltage motors. The shaft voltage, which adversely affects the bearing by occurring bearing current, is induced by parasitic components and the leakage flux in motor-driven systems as well as inherent linkage flux between main magnetic flux and shaft according to rotor configuration. Thus, shaft voltage should be analyzed and considered under inverter-driven and non-inverter-driven conditions because inherent linkage flux can analyze under non-inverter-driven condition. In this study, we designed re-arrangement magnet and re-structuring rotor to minimize the shaft voltage. In addition, we optimized the proposed models. The shaft voltage suppression effect of the designed model was validated experimentally and by comparative finite element analysis.

A survey of shaft voltage reduction strategies for induction generators in wind energy applications

Common mode voltage generated by PWM inverters and the parasitic couplings of the machine structure in high frequencies create a model for the system which leads to an induced voltage on the shaft. Shaft voltage became a dominant side effect of power electronic converters since they are widely used in wind turbine applications to prepare desirable frequency and suitable control on active and reactive power. This voltage is known as the main cause of many unwanted problems such as leakage current, ball-bearings damages and reduction of generator's life time. In this paper, pulse width modulation strategies have been presented for two-level and three-level back-to-back AC–DC–AC converters in order to reduce or eliminate common mode voltage of these converters for reduction or elimination of shaft voltage in squirrel cage and doubly fed induction generators. Applying these techniques lead to complete elimination of shaft voltage for squirrel cage Induction generator with back to back AC/DC/AC converter and a 66 percent reduction of the shaft voltage generation in the Doubly Fed Induction Generator. Simulation results and mathematical analysis have been presented to investigate proposed techniques.

Common-mode voltage reduction in a motor drive system with a power factor correction

Common-mode voltage generated by a power converter in combination with parasitic capacitive couplings is a potential source of shaft voltage in an AC motor drive system. In this study, a three-phase motor drive system supplied with a single-phase AC-DC diode rectifier is investigated in order to reduce shaft voltage in a three-phase AC motor drive system. In this topology, the AC-DC diode rectifier influences the common-mode voltage generated by the inverter because the placement of the neutral point is changing in different rectifier circuit states. A pulse width modulation technique is presented by a proper placement of the zero vectors to reduce the common-mode voltage level, which leads to a cost-effective shaft voltage reduction technique without load current distortion, while keeping the switching frequency constant. Analysis, simulations and experimental implementation have been presented to investigate the proposed method.