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.

Cloth microwave heating drying apparatus

Abstract: The utility model discloses a cloth microwave heating drying apparatus. It includes the microwave oven, the feeding roller, the discharge roller, the variable frequency drive motor, exhaust wet fan, the heat extraction fan, a weighing sensor and a temperature sensor, the temperature controller, PLC controller and humidity transducer, the feed inlet and the discharge gate punishment of microwave oven do not are provided with the feeding roller, the discharge roller, the feeding roller, the discharge roller all links to each other with the variable frequency drive motor, be provided with temperature sensor in the microwave oven, temperature sensor passes through the temperature controller and links to each other with the PLC controller, the PLC controller still with the microwave oven on exhaust wet fan, the heat extraction fan links to each other, the discharge gate department of advancing of microwave oven still is provided with humidity transducer, humidity transducer passes through the PLC controller and links to each other with the variable frequency drive motor. The utility model discloses simple structure can conveniently control heating temperature and input speed, guarantees that the cloth heating is even, and its stoving is effectual.

A new normal mode dv/dt filter with resistor failure detection circuit

Abstract: Insulated Gate Bipolar Transistors (IGBTs) will soon be replaced by wide band gap devices (SiC and GaN) as the choice for power semi-conductor switch in Voltage Source Inverters. These devices have extremely fast rise time and fall time compared to IGBT devices. The high dv/dt of PWM outputs create excessive voltage stress in the insulation system of AC motors due to voltage reflection issues associated with motors at large distances from the drive. In many oil field applications, the distance between the motor and the Variable Frequency Drive (VFD) approaches 300m. In walking rig applications, it is common to use multiple smaller sized conductors per phase, bunched together, to achieve the desired ampacity. This practice results in higher than usual value of the cable parasitic capacitance. Traditional dv/dt filters used for mitigating over-voltage at motor terminals, have been found to be inadequate in reducing the over voltage at the motor terminals in such oil field installations. The damping resistor often experiences high voltage and gets damaged. A new dv/dt filter suitable for use with high power AC motors at distances nearing 300m with a built-in resistor failure detection circuit is proposed here. Test results are given to demonstrate its efficacy.

Reducing electromagnetic noise detected in surface measurements

Abstract: A method for reducing noise at a wellsite includes transmitting a plurality of first signals from a variable frequency drive (VFD) to an alternating current (AC) induction motor. A timing of a plurality of second signals is varied to control transistors in an inverter of the VFD, thereby reducing harmonic distortion of the first signals output from the VFD. The timing is varied based at least partially upon an estimation of the harmonic distortion.

Variable Frequency Control of Induction Motors for Emergency Demand Response

Abstract: The frequency variable drivers of induction motors are typically used to control mechanical load. In the paper a frequency control method is proposed to affect regime of the grid that feeds these motors. The method provides successful self-starting or restarting after significant power disturbance of group induction motors. The proposed strategies are applicable for smart grid, for example, demand response technology works well for industrial loads. It is can be useful not only for normal regimes but in case of emergency, for instance, dynamic demand provides accurate control of the load. Both technologies (demand response or dynamic demand) are well integrated in smart grid concept.

Well pump motor driver control apparatus and method

Abstract: The present invention relates to a circuit for providing conditioned alternating current to a motor for running a well pump reciprocating motor which experiences uneven torque. A system is provided for conditioning the primary electrical supply 310, bussing the conditioned primary service 318 to a variable frequency drive apparatus VFD 336 which alters the line frequency of the alternating current to a controlled frequency to change the speed of the motor in response to a signal received from a well controller 330, and, if the system begins to inductively regenerate current when the speed of the rotor exceeds the line frequency from the drive, to condition and shunt the excess direct current R to the primary supply side 318 of the variable frequency driver where it may be reused.