About: Variable-frequency drive is a(n) research topic. Over the lifetime, 837 publication(s) have been published within this topic receiving 5691 citation(s). The topic is also known as: VFD.
Papers published on a yearly basis
••06 Oct 1996
TL;DR: Novel modifications to the PWM modulator as well as external hardware apparatus are proposed solutions to the >2 pu overvoltage problem, both are simulated and experimentally confirmed.
Abstract: This paper investigates overvoltage transients on AC induction motors when connected through a cable of arbitrary length to a variable frequency drive (VFD) consisting of a pulsewidth modulation (PWM) inverter with insulated gate bipolar transistor (IGBT) power devices. Factors contributing to a motor overvoltage transient equal to a theoretical twice DC bus voltage are first described using existing transmission line analysis. A critical cable distance I/sub c/ is defined where this 2-pu overvoltage occurs. However, literature is lacking on flow motor voltage transients >2-pu bus voltage and up to 3-4 pu are generated. This phenomenon is observed on all PWM inverters with output cable lengths greater than l/sub c/ distance. Contributing factors to the >2-pu overvoltage phenomenon are investigated by exploring the complex interaction between drive modulation techniques, carrier frequency selected, cable natural frequency of oscillation, cable high-frequency damping losses, and, to a lesser extent, inverter output rise time. Theoretical calculations of cable frequency and damping are correlated with simulation and experimental results. Novel modifications to the PWM modulator, as well as external hardware apparatus, are proposed solutions to the >2-pu overvoltage problem; both are simulated and experimentally confirmed.
14 May 2007
TL;DR: In this paper, the benefits of variable frequency drive (VFD) technology more accessible to pump users are discussed, including protection, reliability, and ease of use not possible with other variable frequency drives.
Abstract: The present invention is a controller specifically for pumps, making the benefits of variable frequency drive (VFD) technology more accessible to pump users. The present invention incorporates pump-specific system optimization software, an industrial grade drive, and a menu-driven user interface, offering protection, reliability, and ease of use not possible with other variable frequency drives.
•28 Feb 2000
TL;DR: In this article, the power electronics components of a variable frequency drive for the motor of a refrigerant system compressor are mounted upon a heat sink and refrigerant from the system condenser is passed through the heat sink by means of a flow line.
Abstract: Apparatus for cooling the power electronics components (27) of a variable frequency drive for the motor of a refrigerant system compressor. The components are mounted upon a heat sink (30) and refrigerant from the system condenser (13) is passed through the heat sink (30) by means of a flow line (32) and returned to the low pressure side of the system. A control valve (40) is mounted in the flow line (32) which throttles refrigerant passing through the line to produce cooling of the heat sink (30) to maintain the temperature of the components within a desired range.
13 Mar 2009
TL;DR: In this paper, a variable frequency drive (VFD) was used to drive a permanent magnet motor and match compressor speed with compressor load, a direct drive impeller that eliminated gearing losses, and magnetic bearings that reduce frictional losses.
Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. The assembly is highly efficient by virtue of a variable frequency drive (VFD) that drives a permanent magnet motor and matches compressor speed with compressor load, a direct drive impeller that eliminates gearing losses, and magnetic bearings that reduce frictional losses. The back-emf produced by the motor provides an intermediate power source for the magnetic bearings in the event of a loss of electrical power. A cooling system provides direct cooling of the rotor with gas refrigerant, and cooling of the stator with liquid refrigerant. Modular construction allows the compressor to be retrofit with upgrades. An inlet guide vane system operates without need for oil lubrication. The use of light metal castings and elimination of gearing reduces the weight to one-third or less of comparably powered conventional units.
12 Jan 1987
TL;DR: In this paper, a pair of switching networks and blocking networks are provided to drive the load for half a cycle in a resonant manner to a high energy state, and then maintained in that high energy states for a predetermined period.
Abstract: An AC power system for a resonant load. A pair of switching networks and blocking networks are provided to drive the load for half a cycle in a resonant manner to a high energy state, and then maintained in that high energy state for a predetermined period. Then the load is driven for half a cycle in a resonant manner to the opposite polarity high energy state, and maintained in that high energy state for the predetermined period. A controller adjustably controls the frequency of switching between the two high energy states and the length of the predetermined period, so that a desired frequency is obtained.
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