RU2095934C1 - Device for excitation of synchronous electric motors - Google Patents

Abstract

FIELD: electric engineering. SUBSTANCE: excitation winding is partitioned into two independent parallel circuits each of which is connected to m-phase power supply through bridge rectifying circuit. Cathode group of one bridge rectifier is connected to anode group of another bridge rectifier through two gates which are connected in opposing. Connection point of anode and cathode of gates which are connected in opposing is connected to zero terminal of power supply. EFFECT: increased stability of electric motors due to forced excitation current, decreased power consumption, decreased losses in power supply. 1 dwg

Description

 The invention relates to electrical engineering, in particular to excitation systems, and can be used to ensure the stability of synchronous electric machines by forcing an excitation current.

A device for exciting synchronous machines is known in which the field winding through a bridge rectifier is connected to an m-phase power source (transformer) [1] This device is the basis of thyristor controlled exciters (TVU) of the type TE-8 and BTE, widely used in gas compressor stations with electric drives. In operating mode, the control system provides a control angle of the thyristor bridge valves close to α + 60 ^o and the output voltage of the TVU is equal to half the maximum. In the boost mode, a = 0 ^o voltage, and the field current doubles. The disadvantage of this device is the low power factor COSФ 0.42-0.505, low quality of the output voltage in the operating mode (distortion factor has a value of K _IS 1.24), increased losses in the power source, increased weight and size indicators, because the power supply is calculated at full power boost mode.

Closest to the invention is a synchronous machine excitation device containing an m-phase power supply, the secondary windings of which are connected to the field winding through a thyristor bridge rectification circuit, an on-off valve, the anode of which is connected to the anode group of the rectification circuit, and the cathode with zero point m -phase power supply made, for example, in the form of a transformer [2]
In normal operating mode, the cathode group and the "zero" thyristor (on-off valve) are on. In the forced mode, the cathode and anode groups work, and the "zero" thyristor is turned off. Thus, in the operating mode, the excitation winding of the synchronous machine is powered from the zero circuit of the rectifier, and in the formative from the bridge. The disadvantage of this device is the quality of the voltage in the operating mode, increased weight and size indicators due to the presence of zero sequence currents.

 The aim of the invention is to improve overall dimensions, reduce losses in the power source and improve the quality of the output voltage.

 The drawing shows a diagram of the excitation device of a synchronous machine.

 The excitation device of a synchronous machine contains an m-phase power source, for example, a three-phase voltage source (transformer), the secondary windings of which are connected through the thyristor bridge rectification circuit to the anode 2 and cathode 3 groups of thyristors and connected to the field winding (to the first half winding) 6.1, which is equipped with independent parallel branch (semi-winding), 6.2, connected through the second thyristor rectification circuit with anode 4 and cathode 5 groups of thyristors to the secondary windings of the m-phase power source . The device also includes a counter-activated first valve 7.1, the anode of which is connected to the anode group of the first of these rectification schemes, and a cathode with a zero point of the m-phase power source, and a second counter-connected valve 7.2.

 The cathode group of the second thyristor bridge rectification circuit through the second on-off valve 7.2 is connected to the cathode of the first on-off valve 7.1.

The excitation device of a synchronous machine operates as follows. In the operating mode, the field semi-windings 6.1 and 6.2 are fed from the power source 1 through the following circuits: cathode group 2, half-coil 6.1, valve 7.1, zero point of the power supply, valve 7.2, half-winding 6.2, anode group 5. To ensure the rated excitation voltage, the thyristor control angle a 0 ^o . In this case, the cathode group 2 and the anode group 5 form a bridge rectification circuit with respect to the secondary windings of the transformer (power source). The device also allows for separate regulation of the excitation current of the semi-windings 6.1 and 6.2, for example, to implement the regime of consumption of reactive power while maintaining the stability of the synchronous machine in the operating mode, which expands its functionality.

In the boost mode, control pulses are applied to all four thyristor groups 2-5 with a 0 ^o , and the excitation current in the semi-windings doubles. Due to the short duration of the boost mode, the calculated capacity is the power of the power source (transformer) in the operating mode, i.e. P _tr P _s • P _s , where P _{s the} total power of the field windings 6.1 and 6.2 in operating mode, K _pm 1.05 is the transmission coefficient for power of the bridge rectification circuit. The magnetic field forcing coefficient when the axes of the excitation half-windings are located at an angle of 90 ^° will be at least 1.4.

In the device adopted for the prototype, in the operating mode, the excitation winding of the synchronous machine is powered by a zero rectification circuit. The estimated power of the power source in the prototype will be P _tr P _rn • P _s , where K _ph 1,345 is the transmission coefficient for power of the zero rectification circuit.

Thus, the use of the proposed device of the excitation system of synchronous machines instead of the device, which is the prototype, allows to reduce the overall dimensions of the power source (transformer) and to reduce its installed power
DP = 1.345 × P _s = 1.05 × P _s = 0.295 × P _s .
In addition, the use of the proposed excitation device of synchronous machines can halve the loss in the power source compared to the prototype.

где
J₂ ток во вторичных обмотках трансформатора, J_fn ток в обмотке возбуждения синхронной машины в номинальном режиме.When using two separate bridge-zero circuits (prototype), the power loss in the power source will be:

Where
J ₂ current in the secondary windings of the transformer; J _fn current in the excitation winding of the synchronous machine in nominal mode.

R _{a the} active phase resistance of the secondary winding of the transformer.

Таким образом, изобретение обеспечит экономию электроэнергии и снижение массогабаритных показателей систем возбуждения синхронных машин.When using the present invention (cascade connection of bridge-node circuits), the power loss in the power source:

Thus, the invention will save energy and reduce the overall dimensions of the excitation systems of synchronous machines.

Claims (1)

 The excitation device of a synchronous machine containing an m-phase power source, the secondary windings of which are connected through a thyristor bridge rectification circuit to the field winding, an on-off valve, the anode of which is connected to the anode group of the rectification circuit, and the cathode with the zero point of the m-phase power supply, characterized in that the field winding is provided with a second independent parallel branch, which is connected through the second thyristor bridge rectification circuit to the secondary windings of the m-phase power supply, and the cathode group of the second thyristor bridge rectification circuit through the second on-off valve is connected to the cathode of the first on-off valve.