Variable-frequency drive

About: Variable-frequency drive is a research topic. Over the lifetime, 837 publications have been published within this topic receiving 5691 citations. The topic is also known as: VFD.

Parameters identification of a 3-phase lc filter used for variable frequency drive based on practical induction motor testing

Abstract: A lot of harmonics exist inherently in the front end of 3-phase rectifier feeding Variable Frequency Drive (VFD) of 3-phase induction motor due to the nonlinearities behavior in such loads. The harmonics cause energy losses and deficiency to the overall system. The goal of this paper is to reduce the harmonics for a variable frequency drive by calculating the equivalent circuit of the 3-phase induction motor and identifying the parameters of a passive filter, which is connected to the input side for the rectifier from the VFD converter. The equivalent circuit for the 3-phase squirrel cage induction motor is achieved according to the results of laboratory tests. The concept of point of common coupling (PCC) is implied into the calculations of harmonics and power factor. The performance of the VFD described is simulated using Matlab /Simulink (2008).

A Low cost modelling of the variable frequency drive optimum in industrial applications

Abstract: A single or three phase asynchronous motors, or known a squirrel cage motors (SCMs) are represent one of generally using in many industrial applications. They are consuming further than half-percent of the total generated electrical energy. This motor is working at its full speed when it is attached to the main AC- supply. Therefore, speed control of asynchronous motor is necessary to industrial applications that require changeable flow control of fluid (air, water and chemical liquid streaming). There are many methods to control the speed of motors, such as changing the stator number of poles, controlling supply voltage, addition series reactor or resistances. The modern method is Volt per Hertz, or scalar control this method applied by changing voltage and frequency of three-phase supply, or by making a V/f equal to a constant value in this method a large amount of energy can be saved. In this study, analysis and practical implemented to variable voltage Variable Frequency Drive or called a VFD. The model enables an exception of a large amount of energy, when connected to control speed of Induction motor. A new simplified method for implemented of an AC Drive system with a moderate price for components was proposed. This method totally based on assembling overall components of AC-Drive. The advantage of this design is simplicity, robustness and ease of tuning as well as manufacturing due to these advantages. This design is very suitable for real time applications as motor speed controller. The experimental results obtained show that design helps to preserve a large amount of energy to the power grid, by a limited starting current of the motor as well, eliminating a voltage flicker at starting and reducing dissipating power during running in long period. Results verified experimentally.

New motor design with conductive micro fiber shaft grounding ring prevents bearing failure in PWE inverter driven motors

Abstract: Variable frequency drives induce shaft voltages onto the shaft of the driven motor because of the extremely high speed switching of the insulated gate bipolar transistors which produce the pulse width modulation used to control AC motors in commercial industrial and even consumer applications. This voltage induced on the shaft becomes great enough to overcome the dielectric of the oil film in the bearing causing bearing discharges known as electrical discharge machining effect. Unless mitigation for these shaft voltages is employed in the motor, the motor's bearings may become damaged from the electrical bearing currents which cause pitting and excessive bearing noise, fluting and finally motor failure. The cause of this problem and commonly applied mitigation methods are discussed as well as a new and highly effective conductive micro fiber shaft grounding ring technology which resolves these problems.

Impulse Voltage-based Test Method for Identifying the Stator Insulation Component with PD Activity for Low Voltage AC Motors

Abstract: IEC 60034-18-41 has been developed as a standard acceptance test to ensure partial discharge (PD)-free operation for improving the reliability of low voltage (LV) variable frequency drive (VFD) motors. Although the test can verify whether PD exists in the stator for a voltage surge with predetermined magnitude and risetime, the information on where PD activity is occurring in the stator insulation is not clearly given. In this paper, a method based on variable risetime surge voltage testing is proposed for identifying the component of the stator insulation system where PD occurs in LV random wound motor stators (turn, phase, or ground insulation). This information can be used for increasing the PD inception voltage for improving the reliability of the motor through insulation system design/manufacturing. The test is implemented with a 4.5 kV variable risetime surge generator prototype. 4 LV ac motors are tested to show where PD is likely to occur in commercial LV motors.

Variable Frequency Drive Importance in an LPG Plant: Case Study

Abstract: The success of any plant is generally fostered by many factors that affect directly the production. The relevant ones are, low capital investment, low operating cost, and high production efficiency. Energy consumption is a key element that influences the operating cost factor. Indeed, the electrical power consumed by electrical motors in an LPG plant constitutes one of the major sources of energy consumption. Motorized systems’ optimization can generate important energy saving, improving and energy efficiency for the following systems: compressed air system, ventilation system and pumping system. Variable frequency drive offers many advantages in centrifugal pumps’ operation. It can improve process control, equipment reliability and cost savings. In this paper, a study of energy saving opportunity in pumping systems using low affinity equations is presented. For this purpose, three factors have been measured: the flow rate, pressure and the electrical power drawn by the electric motor. Energy efficiency of the existing system consisting of the pump driven by the electrical motor has been calculated using on site measured data.