Showing papers on "Variable-frequency drive published in 2001"

Machine tool with servo drive mechanism

Abstract: A machine tool has a cam shaft and indexing drive mechanism which is driven by a servomotor and is therefore adapted for operation within a wide range of operational parameters. An encoder mechanism provides feedback to the servo drive mechanism to effect operational control. The machine tool further comprises a variable frequency drive motor which operates the spindles of the machine tool independently of the cam shaft and indexing drive. A servo-operated threading mechanism is operable at one or more workstations of the machine tool to provide threading of parts manufactured thereby. A computer control system controls and monitors the entire operation of the machine tool.

Synchronous generator having auxiliary power windings and variable frequency power source and method for use

Abstract: A synchronous generator is disclosed having main power windings and auxiliary power windings, where the auxiliary power winding is coupled to a variable frequency drive system The variable frequency drive causes the generator to function as a motor and turn a drive shaft to start a gas turbine Switching circuits are used to connect and disconnect the auxiliary windings of the generator with the variable frequency power supply

Power supply for electrically heated subsea pipeline

Abstract: A power supply system for electrically heated pipelines is provided. A variable frequency drive supplies power to the pipeline from an external source of electrical power. An isolation transformer and a contactor or isolating switch may be used between the variable frequency drive and the pipeline. A controller may be used in the system to control special sequences of power level and other needs for heating a pipeline.

Method for boosting the output voltage of a variable frequency drive

Abstract: A sine wave filter including an inductor for each phase (three inductors) and three delta- or Y-connected capacitors is employed within a borehole power system, coupled within a three phase power system at the surface between the output of a variable frequency drive and a three phase power cable transmitting power to a borehole location, and boosts the output voltage of the drive The sine wave filter is designed to have a resonant frequency higher than the maximum operational frequency of the drive, and a Q such that, at the maximum operational frequency of the drive, the filter provides a voltage gain equal to the ratio of the desired voltage to the drive's maximum output power at the maximum operational frequency The sine wave filter also smooths the voltage waveform of a pulse width modulated variable frequency drive

System specific fluid flow control with induction motor drive

Abstract: An apparatus and method for controlling a motor/blower system to provide a constant fluid flow by iteratively loading revised stator frequency values and stator voltage values to a variable frequency drive. Target DC bus current values corresponding to constant fluid flow rates are predetermined and stored as a function of the desired fluid flow rate, the operating frequency, and system specific constants or calculated by the controller as a function thereof during system operation. Actual DC bus current is measured with a current sensor and compared with the target DC bus current. Operating frequency is estimated using a PI controller based on the difference between measured and target DC bus current values. Operating voltage values corresponding to operating frequencies and system specific constants are predetermined and stored in memory or calculated by the controller during system operation. An updated target DC bus current, operating frequency and operating voltage are determined upon each iteration. The updated operating frequency and operating voltage are loaded as control variables to the variable frequency drive upon each iteration.

Induction motor-controlling device

Abstract: PROBLEM TO BE SOLVED: To save power, and to miniaturize inverter power supply capacity. SOLUTION: In a control means 7, a frequency detection means 8 for detecting an operating frequency (f) of an inverter 2 while the variable frequency of an induction motor 3 is being driven, and a target value setting means 10 for setting the various target values are connected, and a clocking means 70 for clocking commercial power supply operation time (t) is incorporated. When the operation frequency (f) of the inverter 2 becomes lower than a frequency (f0) of the commercial power supply and reaches a setting frequency (f1) being preset by the target value setting means 10 or more, a switching means 5 for connecting the inverter 2 to the induction motor 3 is opened, and a switching means 4 for connecting the commercial power supply 1 is closed for changing to commercial power supply operation. When the commercial power supply operation time (t) being clocked by the clocking means 70 becomes setting time (t1), the switching means 5 for connecting the inverter 2 to the induction motor 3 is closed, and the switching means 4 for connecting the commercial power supply 1 is opened for changing to variable frequency drive by the inverter 2.

Synchronous generator having auxiliary power winding and variable frequency power source and its using method

Abstract: PROBLEM TO BE SOLVED: To provide a method and system for starting a gas turbine by using a generator. SOLUTION: The auxiliary power winding 54 of a synchronous generator 50 having a main power winding 52 and the auxiliary power winding 54 is coupled to a variable frequency drive system 60. A variable frequency driving section causes the generator 50 to function as a motor and to turn a drive shaft to start the gas turbine 63. The auxiliary winding of the generator 50 is connected to and disconnected from a variable frequency power unit by using a switching circuit 64. COPYRIGHT: (C)2002,JPO

Axial magnetic couplings for large machine drives

Abstract: A range of magnetic eddy current couplings has been launched in the USA. They claim to offer the principal benefits of efficient operation, vibration isolation, no maintenance and seizure protection and have found wide application in blowers, compressors, conveyors and pumps. More recently, a new range of variable speed couplings for pumps, fans and blowers have been developed. These effectively vary the slip speed in the coupling by using a simple mechanical system for controlling the airgap. The load speed can thus be varied mechanically from a fixed speed motor source. The variable-speed units offer significant cost savings compared to the cost of a variable frequency drive system (VFD). This paper discusses the benefits of the couplings, their design, analysis and performance. (4 pages)