SU1603515A1 - A.c. electric drive - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to simplify and reduce the cost. For this purpose, a diode 8 connected in parallel with the excitation winding of the synchronous machine 1 is introduced into the AC drive, since Since the rotor winding is closed to the diode 8, then a direct current flows in it, the magnitude of which, and therefore the starting torque, is determined by the resistance of the winding and the diode. The direction of current flow in the rotor winding and its rotation is determined by the direction of turning on the diode 8. Switching it can be used for reverse. 4 il.

Description

The invention relates to electrical engineering and can be used to start synchronous 50 Hz MEASCHNES from a 50 Hz unregulated industrial network or in cases of other networks or machines that match or are close to each other.

The purpose of the invention is to simplify and reduce the cost of the device for starting.

Fig, 1 shows the structural scheme of the AC drive; figure 2 is a synchronous machine, the cut in fig.Z and 4 - time diagrams ..

The AC electric drive (figl) contains a synchronous machine 15 a thyristor converter 2 with: direct connection, current sensors 35 in the phases of a synchronous machine, a rotor position sensor b, connected to control system 7, and a diode which is connected between the ends of the synchronous field winding machines 1.,

In figure 2, numerals from 9 to 12 designate characteristic rotor positions. The angular position of the rotor is indicated by an angle of 5 which forms the axis of the rotor pole with a plane equivalent to the foot of the coil phase of the stator winding (for example, phase A)

Figures 3 and 4 show timing diagrams for different frequencies of rotor rotation — in FIG. 3 for the initial start-up phase (21.4 Hz as an example); in Fig. 4, for the final stage of the start-up (as an example, 42.8 Hz); Fig. 3 and 4 show the voltages (s) and current (i), respectively, of the phases AjBjCj; d) the angular position of the rotor relative to the phase A of the stator winding as a function of the angle with which determines the direction and current of the current phase A of the stator winding; e) current in phase A of the stator winding, as well as the signals of the rotor position sensor (rf motor signals above the x-axis), which correspond to the resolution of the interwave, 1p-1 pulses of positive semicircle, when the axis of the rotor pole between mi 12-9-10, when cos jf 0, and rassoesgenshe interchambers; t the passage of pulses negative; polarity of polarity:; T ... T correspond to the pauses between the signals of the rotor position sensor S when the axis of the pole

g

tO

15

20 25

thirty

35 40 45

50

five

the rotor is between positions 10-11-12, when cos O; (e) the angular position of the rotor relative to phase A of the stator winding as a function of the angle sinj, which determines the magnitude and polarity of the voltage induced in the rotor winding; g) the voltage induced in the rotor winding; h) the current in the rotor winding.

The drive works as follows. Control signals for unlocking the corresponding thyristors of the anode or cathode group of converter 2 are generated in the control system 7 when the conditions are simultaneously fulfilled:

1) current. the previous pulse flowing in the phase of the stator winding of the machine became zero (the pulse is completed); at this moment of time from the current sensor of the corresponding phase 3, 4.5, a signal arrives at the corresponding input of the control system,

2) the rotor is in a position where the current pulses create a positive rotational moment, this is determined by the signals of the rotor position sensor 6 — the presence of a signal is the resolution for the passage of positive polarity pulses, the absence of a signal (pause) is the resolution for the passage of negative polarity pulses.

When the specified conditions are met in the control system, control signals are generated for unlocking the thyristors, which are fed to the control inputs of the thyristors, respectively, of the cathode or anode group, depending on the signal from the rotor position sensor. In this case, the thyristor is unlocked, which has the highest positive voltage (from the anode group) at the anode, or, respectively, the one with the lowest negative voltage (from the cathode group) with the cathode.

The conditions for creating torque and transforming from a stator into a rotor are orthogonal in the machine, i.e. The position of the rotor at which the maximum torque is created, and the position of the rotor at which the maximum voltage transformat from the stator to the rotor takes place, differs 5

are relative to each other on

90 el.

The rotational moment is determined by the suppression

Mgp C.l.lgcosy,

the alternating voltage transformed from the stator to the rotor is defined by the expression "

Up C.

where If is the stator current;

Ig is the excitation current; Y - the angular position of the rotor; and - voltage on the stator winding; K - transformation ratio

from stator to rotor; ; C, C2 constructive constants

cars.

As follows from the diagrams in Fig. 3, the positive current pulses flow in the stator phase winding (for example phase A) during the period of time when the magnetic axis of the rotor pole is between positions 12-9-10 (when), T, e. The pulses are located within the signal of the rotor position sensor. Accordingly, a current pulse of negative direction flows during a period of time when the magnetic axis of the rotor pole is between the positions 10-11-12 (when) 5, i.e. the pulses are located within the pauses between the signals of the rotor position sensor. The current pulses in the phase of the machine (fig.Z, 4d) flow from different phases of the network (Fig.3.4 a, b, c). Over each current pulse is the phase of the network (A, B or C) that conducts the current pulse. Such a control is possible, Kor and the T-Oka impulse partially extend beyond the allowed interval. However, in this case, the average value of the ment created by this pulse is always positive, in the limiting case it is zero; as, for example, for the last current pulse within the allowed interval (fig „3, .4 d)

During the current flow time of the pulse, the voltage of the corresponding phase of the network that generated this pulse, through the open thyristor of the drickle, goes to the stator winding. For example, during the flow time

)

15

20

25 30 s - ,, 0 g. y-50

its voltage in the current pulse diagram from the C phase of the network (Fig.3,4) is applied to the stator winding section of the phase voltage C .; The diagram is enclosed between vertical lines. In accordance with expression (2), this voltage, multiplied by K and sinjj, is applied to the rotor winding (Fig, 3.4 g). Further, in the same way, the voltage segments of the corresponding mains phases are applied to the rotor winding, depending on what the mains phase conducts and the current fflyls. The voltage induced in this way into the rotor winding is shown in Fig. 3.4 g. This voltage is a variable voltage, possibly with pauses, with a certain amount of wicking harmonics. Since the rotor winding is short-circuited through diode 8, a half-wave rectification of this voltage takes place and a constant current flows in the rotor winding.

The rotor windings of the type of synchronous machines have a high inductance and relatively. low active resistance, correspondingly large time span. At the same time, the current in the field winding has a rather smooth form (Fig. 3.4 g). Although, in principle, to create 1 shunt moment, the smoothness of the form of the excitation current is not necessary.

The magnitude of the current in the rotor winding is determined by the resistance of the excitation winding and the resistance of the diode in the forward direction. The direction of the direct current flowing in the winding is determined by the direction of the short-circuit switching on of its diode. The direction of the excitation current, in its turn, determines the direction of the excitation flow and, accordingly, the direction of rotation of the rotor. Switching the shunt diode, by the way, the molset can be used to reverse the machine.

As follows from the comparison of the diagrams for figs. 3 and 4, given for different rotational frequencies, self-ejection of the machine is ensured regardless of the rotational frequency.

This device can be used (used to start high-power synchronous motors, compensators, as well as synchronous generators of power plants launched from the network without using a drive motor (turbine) for using the generator in the synchronous compensator mode.

The invention creates a techno-economic effect in all those cases when the synchronous machine starts up has a machine driver that is installed on the same shaft as the synchronous manual one and cannot be used to excite the machine during start-up, therefore a special pathogen.

The technical and economic effect of the use of the invention and |: 1 of the invention is created in. as a result of reducing the cost of | :: triggers for start-up due to the exclusion of a special driver with the introduction of a single diode instead, the resistance of which is incommensurably less than the cost of the driver.

Claims (1)

Invention Formula An AC motor drive containing a synchronous machine with a core winding and excitation, a thyristor frequency converter with direct connection, the output of which is connected to the outputs of the winding core of the synchronous machine through current sensors, the control system, some inputs of which are connected to the outputs of current sensors the rotor position sensor of the synchronous machine, and the outputs are connected to the control inputs of the thyristor converter, characterized in that, in order to simplify and reduce the cost, a diode is inserted into it , Connected chenny parallel excitation winding synchronous machine. I s well C A B ™ i , fc7 Zlk Fig.Z but AT d e Compiled by V.Tarasov Editor L.Pcholinska Tehred M.Didyk Proofreader A.Osaulenko Order 3393 Circulation 455 EiHHHIIH State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Ra Shzska Nab. A b .vyvy Fivl Subscription