International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
www.irjet.net
Brushless DC Motor Drive Using an Isolated-Luo Converter for Power factor correction Ajin Sebastian1, Eldhose K A2, Thomas P Rajan3 1
PG Scholar, Department of Electrical and Electronics Engineering, Mar Athanasius College of Engineering,
Kothamangalam, Kerala, India 2,3Assistant
Professor, Department of Electrical and Electronics Engineering, Mar Athanasius College of Engineering, Kothamangalam, Kerala, India
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Abstract - A brushless DC (BLDC) motor has several application in medical, industrial, aeronautical field. A configuration of Luo converter with high frequency isolation for feeding brushless DC (BLDC) motor drive with power quality improvements at AC mains is presented. A low frequency switching of the voltage source inverter (VSI) is used for reducing the switching losses associated with the six solid-state switches of VSI (Voltage Source Inverter). This is obtained by electronic commutation of BLDC motor and adjusting the DC bus voltage of the VSI for speed control. The isolated- Luo converter is designed in discontinuous inductor current mode (DICM) for voltage control and power factor correction is achieved inherently at the AC mains using a single voltage sensor. Performance of drive is evaluated for improved power quality at AC mains for varying speeds and supply voltages. The simulation of the circuit is done in PSIM and results are obtained. Key Words: BLDC (Brushless DC), Discontinuous Inductor Current Mode (DICM), Voltage Source Inverter (VSI),
1. INTRODUCTION Using of Permanent Magnet in electrical machines have so many benefits and advantages than Electromagnetic excitation machines these are zero excitation losses result in high efficiency, simple construction, low cost maintenance and high torque or high output power. In early 19th century permanent magnet excitation system was used for first time in electrical machines [1]. The performance of this machine was very poor due to low quality of hard magnetic material make this less usable. After the invention of alnico invigorated the use of permanent magnet excitation system increases. Rare earth permanent magnets increases the power density and dynamic performance of the machine [1]. The high power to weight ratio, high torque, good dynamic control for variable speed applications, absence of brushes and commutator make Brushless dc (BLDC) motor, good choice for high performance applications. Due to the absence of brushes and commutator the mechanical wear of the moving parts can be avoided. Moreover, better heat dissipation property and ability to operate at high speeds make them superior to the conventional dc machine [2]. Conventionally, a combination of diode bridge rectifier (DBR) and DC bus capacitor is used for feeding the BLDC motor. However, such combination draws highly distorted current from the supply system, which is rich in harmonics and results in very high total harmonic distortion (THD) of supply current at very low power factor [1]. Hence power factor correction (PFC) converters are used for meeting these recommended guidelines of IEC61000-3-2. A PFC converters are generally designed for their operation in continuous or discontinuous conduction mode. The current in inductors or the voltage across capacitors remains continuous or becomes discontinuous in these modes of operation, respectively. A continuous inductor current mode (CICM) requires sensing of supply voltage (vs),DC link voltage (Vdc) and input current (iin) for the voltage control with PFC operation [6]. This offers reduced stress on the solid-state switch of PFC converter but at the cost of high number of sensors. However, a PFC converter operating in discontinuous inductor current mode (DICM) requires only single voltage sensor for voltage control and inherent PFC is achieved at AC mains. But, the stress on PFC converter increases in this mode of operation and, therefore suitable for low and medium power applications [18]. The Luo converter is widely used in DC-DC conversion as it exhibits good voltage regulation over a wide range of voltage fluctuations and possess high light load efficiency. This paper explores a new configuration of an isolated-Luo converter for feeding BLDC motor drive with sensor reduction and power factor correction
2. BLDC MOTOR DRIVE FED BY AN ISOLATED-LUO CONVERTER Fig. 1 shows proposed PFC based isolated-Luo converter fed BLDC motor drive. A single-phase DBR followed by an isolatedLuo converter is used for control of DC bus voltage with power quality improvements at AC mains. The proposed isolatedLuo converter is designed to operate in DICM, i.e. the magnetizing inductance (Lm) of the high frequency transformer operates in discontinuous current conduction.
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