Method for contactless excitation of a synchronous generator

Abstract

The invention relates to the field of electrical engineering, and more particularly to the control of electric machines. The technical result consists in the efficient controllable operation of an electric machine across all ranges of revolution, from ultra-low to full speed. This technical result is obtained as follows: prior to the start-up of a synchronous generator, a primary winding of a pilot exciter of a rotor that is configured in the form of a multipole primary excitation electromagnet is fed with alternating current in order to create a current in inductors of the main poles of the synchronous generator until the generator reaches its working speed, whereupon the synchronous generator switches to a control mode in which direct current is fed to the primary winding of the pilot exciter.

Description

[0001]IPC: H02K23 / 04 Method for contactless excitation of a synchronous electric generator with a contactless subexciter without the use of permanent magnets. The invention relates to electrical engineering in terms of controlling the operating mode of electrical machines. A known axial contactless alternating current generator (patent RU2643196C1) excites the main poles using permanent magnets rotating with the main poles of the generator. A disadvantage of this design is the uncontrolled excitation current, which depends on the rotor speed and has a low value at low speeds, and the heating of the axial magnetic core of the subexciter by the inductor magnets, resulting in overexcitation at high speeds.A method for starting a gas turbine engine using a brushless salient-pole synchronous generator with a rotating rectifier is known (patent RU2524776C1). The generator is started in motor mode and excitation is supplied with direct current to the salient-pole winding of the brushless exciter, followed by rectification of the induced current on the rotor side and its supply to the main pole coils. A disadvantage of this type of starting is low starting torque due to insufficient current induction in the rotor winding of the exciter at low speeds and, consequently, low current in the generator's main pole windings. A high-speed brushless electric machine is known (patent RU2534756C1) with armature excitation via a rotating transformer with a rotating rectifier. A disadvantage of this excitation method is the presence of torque pulsations on the armature shaft with a frequency double that of the rotating transformer voltage.The objective of the present invention is to improve the performance of synchronous electric motors and generators with a contactless exciter without the use of permanent magnets. The technical result consists of efficient, controlled operation of the electric machine at all speed ranges—from ultra-low to maximum. This technical result is achieved as follows: before starting the synchronous electric generator, alternating current is supplied to the primary winding of the rotor exciter, which is a multi-pole main excitation electromagnet. This current creates a current in the coils of the main poles of the synchronous electric generator until it reaches operating speed. The synchronous electric generator then switches to control mode, supplying direct current to the primary winding of the exciter.This excitation method is applicable to increasing the dynamic range of synchronous electric machines in electric transport, wind and hydroelectric power generation, and other applications requiring improved machine performance and controllability. To implement the claimed method, the electric machine rotor is designed as a multi-pole main excitation electromagnet powered by a subexciter with a fixed primary and movable secondary windings and a rectifier diode bridge at the output, all located on a common shaft. Excitation control is achieved by applying direct current to the fixed primary winding of the subexciter.The advantage of such electric machines is their controlled contactless excitation, which allows for the main pole strength to be adjusted depending on the machine's speed and for their disconnection in emergency situations. The claimed method involves applying alternating current to the primary winding of the rotor's exciter, which is a multi-pole main excitation electromagnet, before starting the electric machine. This current creates a current in the coils of the main machine's poles until the machine reaches operating speed. The machine then switches to normal control mode, supplying direct current to the primary winding of the exciter. A practical example of this contactless excitation method was tested on a synchronous gasoline generator with a multi-pole exciter. In a normal circuit, direct current is applied to the primary winding of the exciter.When the rotor is stationary, there is no voltage on the secondary winding of the exciter and no poles on the generator rotor. Under test conditions, single-phase AC voltage was applied to the primary winding of the exciter, resulting in normal magnetic poles forming on the surface of the generator rotor with the rotor stationary. When the rotor began to rotate, voltage immediately appeared at the generator output, which was not observed with the standard excitation circuit. In the standard design, generation began at 160–200 rpm. Thus, by using this method, the generator gained the ability to efficiently generate electricity from the very beginning of rotor rotation. Using this method in an electric vehicle motor will also allow for high torque at startup, as soon as the motor shaft begins to rotate.

Claims

Claim of the invention A method for contactless excitation of a synchronous electric generator with a contactless sub-exciter without the use of permanent magnets, which consists in the fact that before starting the synchronous electric generator, alternating current is supplied to the primary winding of the rotor sub-exciter, made in the form of a multi-pole electromagnet of the main excitation, to create a current in the coils of the main poles of the synchronous electric generator until it reaches operating speed, then the synchronous electric generator switches to control mode with the supply of direct current to the primary winding of the sub-exciter. 1