AC7 matrix converter

AC7 matrix converter

Doc#: AN.AC7.01 Copyright Yaskawa Electric America, Inc. ©2008 www.yaskawa.com April 14, 2008 1/4 Application Note AC7 Matrix Converter The combination of an adjustable frequency drive (AFD) and motor has enjoyed widespread use because of its excellent energy-saving capabilities. Despite these advancements, there are still issues to be conquered such as the suppression of input power harmonics and the effective use of electric energy regenerated during deceleration. In order to fully solve these technical issues, Yaskawa is the first in the world to commercialize the AC7 Matrix Converter: a new technology that converts the AC power source directly into a variable AC output. This paper shows the data and outlines the AC7 Matrix Converter principle, PWM method, and input current control. It also explains the specifications and features of the AC7 Matrix Converter. 1. Introduction With the depletion of energy resources and the increase in energy consumption, energy conservation is becoming a high priority in many sectors. Energy conservation has become a key issue in the field of motor drives, and the use of PWM drives is increasing as one effective means of reducing energy consumption. Major applications include industrial uses such as converting, transport, and fabrication, as well as commercial applications such as fans and pumps for indoor comfort. In recent years, the growing use of PWM drives has led to increased focus on the various problems inherent in drives, such as insulation failure due to surge voltage at the motor terminals, bearing fluting electro-corrosion due to shaft potential, and other output-side problems. Other difficulties include input-side issues such as the effects on power supply equipment and other systems connected in parallel running off the same power supply. To resolve these problems, Yaskawa has commercialized drives such as the G7 with 3-level PWM control technology to control surge voltage and leakage current and the DC5 sine- wave PWM converter permitting input power supply regeneration and control of input power supply harmonics. The latest technology in this area is the AC7 Matrix Converter, the first of its type in the world, offering improvements in motor drive environmental characteristics including motor surge voltage, power supply harmonics, and shaft potential. 2. Basic Principles of the Matrix Converter Unlike conventional voltage-type PWM drives, the AC7 uses matrix conversion technology for direct conversion of AC to AC [1]. Features such as power supply regeneration and suppression of power supply harmonics make it an ideal choice as a drive for applications where regenerative operation is highly beneficial, such as elevators, escalators, centrifuges, and test stands. The main circuit for a matrix converter consists of a compact input filter and nine bidirectional switches (Figure 1). The bi- directional switches are made up of IGBTs and diodes. The basic characteristics of this type of matrix converter are discussed below. Figure 1: Diagram of Main AC7 Matrix Converter Circuit 2.1 PWM method The AC7 uses PWM switching to output power from the three-phase AC power supply at a specified voltage and frequency. Figure 2 below shows an example of a PWM- switched waveform. In Region 1, switching of the R phase (maximum voltage) is handled referenced to phase T voltage with intermediate voltage phase S. Compared to a 2-level drive, there is less voltage change per switch operation, consequently reducing motor terminal surge voltage and leakage current. Figure 2: Sample AC7 Matrix Converter PWM Waveform Doc#: AN.AC7.01 Copyright Yaskawa Electric America, Inc. ©2008 www.yaskawa.com April 14, 2008 2/4 Application Note Figures 3a and 3b below show the surge voltage created by a conventional 2-level drive (Figure 3a) and the AC7 Matrix Converter (Figure 3b). The distance between the motor and drive is 328 ft. (100 m). The AC7 Matrix Converter suppresses surge voltage by 20 to 50%. Figures 3a and 3b: Surge Voltage Waveforms at the Motor Terminals (328 ft. (100 m) of Motor Cable) 2.2 Input current control The AC7 Matrix Converter can use all three input phases in PWM switching to control output voltage and input current [3]. This is also possible during regenerative operation, combining the merits of being able to suppress power supply harmonics through current control as well as saving energy through regeneration. The power factor is about 1 while motoring and about -1 during regenerative operation. Figures 4a and 4b show the input line voltage and current waveforms during motoring and regenerative operation. Figure 5 shows the input current harmonic wave ratio and distortion, indicating that total harmonic distortion (THD) during both motoring and regenerative operation is kept to no more than 7%, thus providing excellent input current control. Figures 4a and 4b: Input Voltage and Current Waveforms Figure 5: Harmonic Wave Ratio and Input Current Distortion (3a) Conventional 2-level Drive (3b) AC7 Matrix Converter (4a) During Motor Operation (4b) During Regenerative Operation Doc#: AN.AC7.01 Copyright Yaskawa Electric America, Inc. ©2008 www.yaskawa.com April 14, 2008 3/4 Application Note 3. Product Outline 3.1 Product Specifications Major specifications for the AC7 Matrix Converter are given in Table 1 with product photos shown in Figure 6. Table 1: AC7 Matrix Converter Product Specifications Figure 6: AC7 Appearance 3.2 Major Features This section introduces the key differences between the AC7 Matrix Converter and conventional drives. (1) Power Supply Harmonics Without any special devices, the AC7 input current THD is 7% maximum, and has a minimum input power factor of 98%. (2) Line Regeneration The AC7 is fully regenerative which greatly improves system efficiency and reduces the need for additional components. (3) Prolonged Life There are no electrolytic capacitors or other short-lived components in the main circuit, providing a long high- performance life. (4) Reduced Motor Shaft Potential The switching waveform is equivalent to 3-levels, making it possible to reduce motor potential, a major cause of bearing fluting electro-corrosion. (5) No Low-Speed De-rating Current is not concentrated in specific devices, eliminating the need for current de-rating during low-speed operation. 4. Conclusion The range of applications for motor drive technology has spread to almost all industries, leading to increased demand for energy conservation, power supply harmonic reduction, and motor friendliness. The AC7 Matrix Converter is the latest Yaskawa innovation in these areas. Item Specifications Applicable Motor Output (HP) 7.5 HP 15 HP 30/40 HP 200/208/220 Vac, 50/60 Hz, 3-phase 380/400/415/440/460/480 Vac, 50/60 Hz, 3-phase 230V 27 A 49 A 96 A Rated Output Current 480V 15 A 27 A 52 A Output Frequency 120 Hz maximum Allowable Frequency Fluctuation Allowable Voltage Fluctuation +10% to -15% Output Voltage Input Voltage x 0.93 (Maximum average output voltage) Control Method Sine-wave PWM Control Modes V/f, Open-loop Vector, Closed-loop Flux Vector Carrier Frequency 4, 8, or 12 kHz Power Rating 100% continuous operation across entire range Overload Capacity 150% rated output for 1 minute Allowable Power Supply Frequency Fluctuation ±3% or less, Frequency Fluctuation Ratio: 1 Hz / 100 ms or less Input Current Control Sine-wave supply; regenerative Input Harmonics Input current THD 7% or less, input power factor 98% or more (at rated load) Momentary Power Loss Compensation Stops at 15 ms outage or more (factory setting). Up to 2 second ride-through possible with parameter setting. Conversion Efficiency 97% or more Height (H) 20.87" 22.05" Width (W) 11.81" 14.17" Dimensions Depth (D) 11.42" 11.89" Weight (lbs.) 64 110 Input Power Ratings ±3% (Frequency Fluctuation Rate: 1 Hz / 100 ms or less) (a) 15 HP (b) 30/40 HP Doc#: AN.AC7.01 Copyright Yaskawa Electric America, Inc. ©2008 www.yaskawa.com April 14, 2008 4/4 Application Note References: [1] Venturini, M., "A new sine wave in sine wave out conversion technique which eliminates reactive elements," in Proc. Powercon 7, 1980, pp. E3-1-E3-15. [2] Watanabe, Ishii and Yamamoto, "Motor Drives Using Matrix Converter Technology" (in Japanese), Yaskawa Technical Review, Vol. 64, No. 247, P. 111 (2000, No. 2). [3] J-K.Kang, H.Hara, et al., "The Matrix Converter drive performance under abnormal input voltage conditions," IEEE Trans. Power Electronics, Vol. 17, No. 5, pp. 721-730 (Sept., 2002). [4] Hara, Yamamoto, Sonoda, "Matrix Converter Drive Varispeed AC", Yaskawa Technical Review, Vol. 69, No. 2, Serial No. 267 (2005). . specifications for the AC7 Matrix Converter are given in Table 1 with product photos shown in Figure 6. Table 1: AC7 Matrix Converter Product Specifications Figure 6: AC7 Appearance 3.2 Major. The basic characteristics of this type of matrix converter are discussed below. Figure 1: Diagram of Main AC7 Matrix Converter Circuit 2.1 PWM method The AC7 uses PWM switching to output power from. a conventional 2-level drive (Figure 3a) and the AC7 Matrix Converter (Figure 3b). The distance between the motor and drive is 328 ft. (100 m). The AC7 Matrix Converter suppresses surge voltage by 20