10 kw axial flux motor12/8/2023 While suitable in wide-ranging applications, V/Hz control is sub-optimal in high-performance applications involving low speed or demanding, dynamic speed regulation, positioning, and reversing load requirements. For example, for 460 V, 60 Hz motors, this linear V/Hz relationship is 460/60 = 7.67 V/Hz. In variable- torque applications suited for Volts-per-Hertz (V/Hz) drive control, AC motor characteristics require that the voltage magnitude of the inverter's output to the motor be adjusted to match the required load torque in a linear V/Hz relationship. Introduced in 1983, the insulated-gate bipolar transistor (IGBT) has in the past two decades come to dominate VFDs as an inverter switching device. Ĭontroller advances have exploited dramatic increases in the voltage and current ratings and switching frequency of solid-state power devices over the past six decades. The drive controller can also be configured as a phase converter having single-phase converter input and three-phase inverter output. VSI drives provide higher power factor and lower harmonic distortion than phase-controlled current-source inverter (CSI) and load-commutated inverter (LCI) drives (see 'Generic topologies' sub-section below). This filtered DC voltage is converted to quasi- sinusoidal AC voltage output using the inverter's active switching elements. In a VSI drive, the DC link consists of a capacitor which smooths out the converter's DC output ripple and provides a stiff input to the inverter. The most basic rectifier converter for the VSI drive is configured as a three-phase, six-pulse, full-wave diode bridge. However, in some applications such as common DC bus or solar applications, drives are configured as DC-AC drives. Most drives are AC-AC drives in that they convert AC line input to AC inverter output. Voltage-source inverter (VSI) drives (see 'Generic topologies' sub-section below) are by far the most common type of drives. The VFD controller is a solid-state power electronics conversion system consisting of three distinct sub-systems: a rectifier bridge converter, a direct current (DC) link, and an inverter. Controller įurther information: FAM control of induction motor Elevated-voltage stresses imposed on induction motors that are supplied by VFDs require that such motors be designed for definite-purpose inverter-fed duty in accordance with such requirements as Part 31 of NEMA Standard MG-1. Motors that are designed for fixed-speed operation are often used. Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical. The AC electric motor used in a VFD system is usually a three-phase induction motor. System description and operation VFD systemĪ variable-frequency drive is a device used in a drive system consisting of the following three main sub-systems: AC motor, main drive controller assembly, and drive/operator interface. Strömberg managed to sell the idea of PWM drive to Helsinki metro in 1973 and in 1982 first PWM drive SAMI10 were operational. Martti Harmoinen is regarded the inventor of this technology. Pulse Width Modulating (PWM) variable frequency drive project started in the 1960s at Strömberg in Finland. VFDs include low- and medium-voltage AC-AC and DC-AC topologies. Since the 1980s, power electronics technology has reduced VFD cost and size and has improved performance through advances in semiconductor switching devices, drive topologies, simulation and control techniques, and control hardware and software. Systems using VFDs can be more efficient than hydraulic systems, such as in systems with pumps and damper control for fans. VFDs are used in applications ranging from small appliances to large compressors. Depending on its topology, it controls the associated voltage or current variation. Small variable-frequency drive Chassis of above VFD (cover removed)Ī variable-frequency drive (VFD, or adjustable-frequency drives, adjustable-speed drives, variable-speed drives, AC drives, micro drives, inverter drives, or drives) is a type of AC motor drive (system incorporating a motor) that controls speed and torque by varying the frequency of the input electricity.
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