Ozgenel, Mehmet Cihat

In this article, this study aims to reduce torque ripple in a brushless direct current motor by employing a three-phase active mode voltage source inverter, and the torque ripple caused by commutation has been studied in detail. In this study, brushless direct current motors with two different pole numbers and central phase windings, which are frequently used in printing machines, were used. Nowadays, six-step two-phase winding active drives are used as brushless direct current motor (BLDC) drives. In conventional two-phase active mode drives, two phases are connected in series at any time, and the voltage at the ends of the phase windings is half that of the direct current source. In this proposed drive, the phase windings are connected in three different ways, creating a stepped-sinusoidal voltage across the phase windings. This voltage across the phase windings ensures that the current flowing through the phase windings is very close to a sinusoidal current. The closer the current flowing through the phase windings is to a sinusoidal current, the lower the torque ripple. Although the phase windings of the BLDC motors used in the study were centered type phase windings, phase currents were close to sinusoidal. The results from this experimental study showed that the torque ripple of the three-phase active mode drive was significantly reduced. In this work, the torque ripple was found to be 12% in two-phase conduction mode, while it was found to be 7% in three-phase conduction mode.

Ozgenel, Mehmet Cihat; Ting, Naim Suleyman; Sahin, Yakup

This paper presents an enhanced soft-switched T-type neutral-point clamped inverter featuring a compact active snubber cell that delivers zero-voltage transition turn-on and zero-voltage switching (ZVS) turn-off for the main switches, while auxiliary switches operate with zero-current switching turn-on and ZVS turn-off. Unlike prior designs, four auxiliary-path diodes are eliminated, reducing component count, conduction path length, and reverse-recovery losses, which in turn lowers cost, eases thermal management, and boosts power density. The proposed topology maintains full soft switching (SS) for all active devices without introducing additional voltage or current stress. The theoretical analysis of the inverter is clarified, and the operating modes for steady-state analysis are presented in detail. Experimental validation on a 400 V, 1 kW, and 100 kHz prototype demonstrates consistent SS across load conditions and a peak efficiency of 97.2%. The combination of higher efficiency, structural simplicity, and cost-effectiveness makes the proposed inverter a strong candidate for high-performance, compact T-type applications in renewable energy, and electric drive systems.

Ozgenel, Mehmet Cihat

With the reduction of magnet costs and the production of high-energy magnets in small sizes, permanent magnet brushless motors are used widely in various applications from household to medical, industrial, and automation applications. Furthermore, permanent magnet brushless motors have some significant advantages over the other conventional motors such as induction and brushed motors. Due to the popularity of brushless motors, they have become the focus of interest of researchers. From the past 30 years to today, the researchers have carried out numerous studies in relation to brushless motors. These studies are generally sensorless control, adaptive control, different Proportional Integral and Derivate (PID) applications, fuzzy control, PI-fuzzy and PID-fuzzy control and different Pulse Width Modulation applications and to eliminate torque ripple and other control algorithms. Permanent magnet brushless motors can be divided into two main groups. One is the permanent magnet synchronous motor and the other one is the permanent magnet brushless direct current motor (BLDCM). BLDC motors are the most preferred in applications due to their low cost and relatively simple drivers. BLDC motors are run with the classical 120-degree conduction mode voltage source inverter (VSI). Because BLDC motors run with 120-degree conduction mode inverters, power and torque produced by BLDC motors are less than their capacity, whereas BLDC motors can provide a better dynamic response, higher power, and torque by employing 150-degree conduction mode controlled VSI. In this experimental study, it is aimed to design and manufacture a versatile VSI which can control the BLDC motor in both 120 and 150-degree conduction modes. Then, BLDC motor is run in two conduction modes employing the purposed inverter under various loads, and the torque, power, and speed performance of the motor were analyzed to demonstrate the effect of the two commutation methods on BLDC motor performance. The results of this comparative experimental study have shown that the 150-degree conduction mode-controlled inverter provides with the BLDC motor generating higher power, torque, and speed than the inverter with 120-degree conduction mode.

Sahin, Yakup; Ting, Naim Suleyman; Acar, Fatih

This paper introduces a novel active snubber cell for soft switching pulse width modulation DC-DC converters. In the proposed converter, the main switch is turned on under zero voltage transition and turned off under zero voltage switching (ZVS). The auxiliary switch is turned on under zero current switching (ZCS) and turned off under zero current transition. The main diode is turned on under ZVS and turned off under ZCS. All of the other semiconductors in the converter are turned on and off with soft switching. There is no extra voltage stress on the semiconductor devices. Besides, the proposed converter has simple structure and ease of control due to common ground. The detailed theoretical analysis of the proposed converter is presented and also verified with both simulation and experimental study at 100 kHz switching frequency and 600 W output power. Furthermore, the efficiency of the proposed converter is 95.7% at nominal power.

Ozgenel, Mehmet Cihat; Bal, Gungor; Uygun, Durmus

This study presents a precise speed control method for Brushless Direct Current (BLDC) Motors using an electronic tachogenerator (ETg) instead of an electro-mechanical tachogenerator. Most commonly used three-phase BLDC motors have three position sensors for rotor position data to provide commutation among stator windings. Aforementioned position sensors are usually Hall-effect sensors delivering binary-high and binary-low data as long as the motor rotates. These binary sets from three Hall-effect sensors can be used as an analogue rotor speed signal for closed loop applications. Each position sensor signal is apart from 120 electrical degrees. By using an electronic circuitry, a combination of position sensor signals is converted to the analogue signal providing an input to a PI speed controller. To implement this, a frequency to voltage converter has been used in this study. Then, the analogue speed signal has been evaluated as rotor speed data in comparison with the reference speed. So, an ETg system has been successfully achieved in place of an electro-mechanical tachogenerator for BLDC motor speed control. The proposed ETg has been tested under various speed conditions on an experimental setup. Employed tests and obtained results show that the proposed low-cost speed feedback sub-system can be effectively used in BLDC motor drive systems. Through the proved method and designed sub-system, a new motor controller chip with a speed feedback capability has been aimed.

Ozgenel, Mehmet Cihat

Permanent magnet brushless dc (BLDC) motors are very convenient for many applications such as industrial, medical, robotic, aerospace, small electric vehicles, and home applications because of their inherent satisfying dynamic characteristics. There are numerous studies about these motors and their control schemes such as sensorless control and different speed and torque control schemes. All electric motors need commutation in order to produce speed and torque. Commutation in brushed DC motors is performed by means of a brush and collector. In BLDC motors, commutation is provided electronically in contrast to the brushed dc motors. In BLDC motors, motor phase windings are energized according to the information of the rotor position by inverter transistors. Rotor position information is used for commutation. Therefore, rotor position information is required to produce speed and torque for BLDC motors. The easiest and cheapest way to obtain rotor position information is to use Hall-effect or optical sensors. BLDC motor manufacturers generally produce BLDC motors equipped with three Hall-effect position sensors. Having three position sensors on BLDC motors provides six-step commutation which ensures two phase windings are energized in each moment. The third phase is empty. In this study, all phase windings are energized in the same time. This commutation method is twelve-step or 150 degrees commutation. So that more speed can be achieved from the same BLDC motor by comparison with six-step commutation. In this paper, both six-step and twelve-step commutation methods applied to the same BLDC motor and obtained experimental results from this study were presented, examined, and discussed.