SU1764000A1 - @-phase rectifier of three-phase synchronous motor rotating diodes short circuit detecting method - Google Patents

Abstract

The invention relates to a control, preferably under operating conditions, of three-phase synchronous machines. The purpose of the invention is to detect the short-circuit of a rotating diode in a t-phase full-wave rectifier of a three-phase synchronous machine. The linear EMF of the winding of the core 1 of the main machine, having a space-time structure, is fed to the input of a three-phase full-wave rectifier 6 loaded from the direct current side to the resistor 7. Rectifier 6 is inserted into the device circuit so that the voltage across the resistor 7 at turning the rotor of the machine. the modulus varied within no more than ЈG / 2 to 3/2 of the maximum value of the phase EMF of the winding 1 core of the main machine. 2 Il. fe VI ON 44 O O o Fi 1

Description

The invention relates to the control, mainly under operating conditions, of three-phase synchronous machines having synchronous reversal exciters with rotating m-phase two-half-full rectifier bridges.

A known method of controlling a phase-phase rectifier of an exciter of a synchronous machine, consisting in rotating the rotor of the machine by an external drive and viewing the EMF curve. induced in the signal coil, specially installed at the pole of the stator of the exciter,

The disadvantage of the method is the necessity of introducing into the machine an additional element in the form of a signal coil, which makes it unacceptable for machines that are in operation and not adapted initially to the control in this method.

There is also known a method for detecting a short circuit (breakdown) of a rotating diode, which consists in detecting the appearance of a variable component of a current in the excitation winding of a synchronous machine exciter when it is rotated by an unauthorized drive, which in a number of cases, for example, when monitoring aviation synchronous generators driven by rotation engines, causes additional fuel and energy costs. In addition, with an increase in the number of phases of the core of a synchronous machine exciter, the sensitivity of the method decreases due to the electromagnetic inertia of the excitation winding of the exciter, which is especially important for high-speed machines.

According to the technical essence, the method of controlling rotating m-phase single-half-rectifier diodes of a synchronous machine exciter is closest to the invention, which means that by connecting the three-phase winding of the core of the main machine to a source of sinusoidal three-phase alternating voltage, in all m phases, the windings are fixed ( non-rotating excitatory core of the exciter coincident in time alternating currents and measure the EMF induced by the resulting magnetic field of these currents in the excitation winding disconnected from the network or pathogens. A smooth rotation of the rotor of the machine within 180 e, achieve the maximum of the indicated emf and, matching it with the reference signal corresponding to the maximum emf value of a single-type machine having a single diode breakage, the malfunction of the rotating rectifier

The connection of the windings of a synchronous machine, having a gl-phase two-wave rectifier, to the AC voltage network according to this method does not

can cause the occurrence of coincident currents in the core phases of the exciter and, therefore, ensure the detection of a short-circuit of a rotating diode of an m-phase two-wavelength switch.

The purpose of the invention is to detect the short circuit of a rotating diode in an m-phase full-wave rectifier of a three-phase synchronous machine.

5 The goal is achieved by the fact that in the method of detecting a short circuit of a rotating diode of an m-phase rectifier of a three-phase synchronous machine, which consists in connecting one of the windings

0 machines to a source of sinusoidal alternating voltage, creating in phases of a winding non-rotating core of a three-phase synchronous machine exciter coincident variable currents, registering EMF in a winding not connected to the source with a smooth rotation of the rotor to the detection of a short circuit based on the comparison of the EMF with the reference value, k the source is connected to the excitation winding of the exciter, register the modules of the linear EMF windings of the core of a three-phase synchronous machine with one complete rotation of the rotor, and achestve taking reference value of the second modulation garmo5 nicks said linear EMF.

FIG. 1 is a schematic diagram of a three-phase synchronous machine having an m-phase full-wave rotary rectifier; in fig. 2 0 the electrical circuit of the device for the implementation of the proposed method.

Synchronous machine (Fig. 1) consists of a three-phase winding 1 of the main machine located on the stator, winding 2

5 of driving the main machine located on the rotor and receiving DC power from the m-phase (in Fig. 1 six-phase) rotating full-wave rectifier 3, m-phase winding 4 core of the inverted synchronous exciter, also located on the rotor, and located on the stator winding 5 excitation of the exciter,

The device (Fig. 2) contains a three-phase, full-wave, full-wave rectifying bridge 6 connected from the AC side to the phases of the winding 1 of the synchronous machine core and loaded from the DC side with a resistor 7, the voltage drop across which the filter 8 is applied to the capacitance After filter 8, the signal is fed to the input of an electronic amplifier 9, the output of which is connected to the second filter 10. From filter 10, the signal is fed to the input of a comparator 11, the output of which is connected to the input of the RS flip-flop 12. Trigger 12, which can forcibly return with the initial state of apparatus 13 (e.g., button), a control device 14 is a light or audible warning of short-circuit of the rotating diodes.

The invention is as follows.

A circular sinusoidal circular frequency frequency, applied to the excitation winding 5 of the exciter, creates in the air gap between the winding 5 and the winding 4 of the exciter magnetic flux Fv, which changes with the frequency w and induces the emf in the winding 4 core.

The value of the emf induced by the flow of the PV in each of the m phases of the winding 4 of the exciter core depends on the electrical angle aРв between the axis of this phase and the axis of the excitation winding 5 of the exciter, because the coupling current with the kth phase of the winding 4 of the exciter core is determined by the formula

0 tt k

FC - FV cos (a RV +), 0)

IT)

where Fv Fv max sin wt; a is the geometric angle of rotation of the rotor of a synchronous machine; Рв - the number of pole pairs of the exciter, m - the number of phases of the winding 4 core of the exciter; k is the sequence number of the phase of the exciter core, counted or some initial phase with the sequence number O.

FIG. 1 phase of the winding 4 core of the exciter, depicted by a thickened line, taken as the initial.

The currents of the windings 4 induced by the currents Φ k k of the exciter core are applied to the diodes of the m-phase rectifier 3 and in the phases of the core 4 they cause coinciding currents in time.

However, these currents cannot simultaneously flow in all m phases of the winding 4 of the exciter core. The current will flow only in those phases 4 of the exciter core, which, at a given position of the rotor of the machine, have a maximum linear EMF. This means that at each given position of the rotor, out of all 2m diodes of a full-wave rectifier 3, only those four diodes are passed through to which a maximum linear EMF is applied, i.e. The hp-phase rectifier 3 seems to be a

0

50

five

0

five

single phase full-wave rectifier,

By smoothly turning the rotor of a synchronous machine within one full revolution, the t-phase 3 full-wave rectifier 3 is successively broken by 2 rvgl single-phase full-wave rectifiers, which makes it possible to successively control all 2t diodes.

Let the axis of the initial phase of the winding 4 of the exciter core coincide with the axis of the excitation winding 5 of the exciter (a 0). Then in the initial phase will be maximum EMF Emax. Exactly the same EMF will be in phase 4, the axis of which is shifted relative to the axis of the initial phase by 180 e. degrees, a linear emf of these two phases, determined by the geometric difference of the phase emf, will be equal to 2Е max.

Linear EMF 2Е max causes the flow of pulsating current I о in the excitation winding 2 of the main synchronous machine.

At the times when the initial phase of the exciter core 4 has a positive potential, the current I 0 will flow along the path indicated in FIG. 1 by arrows on a thickened line, and at times when this phase has a negative potential, along the path indicated by arrows marked next to a thickened line,

Assuming the symmetry of the current-voltage characteristics of the diodes of the t-phase rectifier 3, the pulsating current 0 is determined by the well-known formula

2Cmox / 5inu) t /

VRoB

-iTRoB

; (

t- 6in4fc3lt

(2)

where ROD is the resistance of the excitation winding 2 of the main machine,

As can be seen from formula (2), the pulsating current i0, along with the constant component, contains harmonics of even order, the main of which is the second harmonic F of the nickname with the amplitude of the mouths.

About 71 K sv

The flow across the excitation winding 2 of the main synchronous machine, the current 10 creates a pulsating flow F0 having the same time harmonics as the current 0.

The magnetic fluxes of phases A, B, C cor 1 of the main machine will be equal

FA Fo cos ("PO + /),

2 t Fv Fo cos (a po + / +),

4tg

Fs fosoz (ar0 + -Ј)

(3)

Here PO is the number of pairs of poles of the main machine, in general, it is unequal to the number of pairs of poles of the driver; / is the electrical angle of shift of the axis of the initial phase of the winding 4 core of the exciter relative to the axis of phase A core 1 of the main machine.

Variable components of FA flows. PV and FS will induce EMF in the phases of the three-phase winding of the core 1 of the main machine, depending not only on the flow Fo, but also on the relative orientation of the axis of the excitation winding 2 relative to the axes of the phases A, B and C of the core of the main machine, as indicated by 3). At the same time, the EMF of phases A, B and C of the core 1 of the main machine depends on the angle of rotation of the rotor not only in value but also in phase, which makes it difficult to implement the method.

As a control signal, it is convenient to use not phase, but linear EMF windings of core 1 of the main machine, proportional to the flux differences fd - fv, fs - fA and fv - fs.

In „, In V3

cos-3- -2: sln-g- -r:

4 1. 4l: v5 cos -s- - -k: sin -j and formulas

(1), (2) and (3) for the linear emf of the core 1 of the main machine receive

EW KEieW5Kp4fC4 Pe P fH (l) lll

 Ew-KEieco5 "p6 -f 6; p (),

YOCA KEi0cos ".p8 - | cos (" p0.fi) 415, n (v fvP),

(four)

where KE is the proportionality coefficient between the variable components of the pulsating current io and the linear emf of the core 1 of the main machine, depending on the parameters of the machine windings.

Formula (4) shows that the linear emf of core 1 of the main machine depends on the angle of rotation of the rotor, both in value and in phase. However, the moduli of the expressions in square brackets cannot vary more than from 3/2

Aof

To simplify the hardware implementation of the method, it is advisable to use as a control signal the linear emf modules of the winding of the core 1 of the main machine, the separation of which is carried out by connecting to the winding of the core 1 of a three-phase full-wave rectifier b (see Fig. 2).

Let the diode of the anode group of bridge 3 be pierced, which is conventionally shown in FIG. 1 arcuate jumper. Then at the moments of time corresponding to the positive potential of the initial phase of the winding 4 of the exciter core, a current 0 will flow along the same path as with all the good diodes of the bridge 3. At a negative potential of the initial phase, the current i0 flows through

the following way: from the phase of the winding 4 core of the exciter, the axis of which is shifted relative to the axis of the initial phase at an angle of 180 e. degrees (or close to 180), and then through the punched diode, mine, the excitation winding 2 of the main machine, to the initial phase of the winding 4 of the exciter core, which is shown in FIG. 1 indicated by crossed-out thin arrows.

Now in the excitation winding 2 of the main machine, the current 0 is described by the formula

V

1 tS (Hsillu {lein2ot 3lBl n Mt + 1 I

Comparing formulas (4) and (5). convincingly — that in the current curve I 0 there is a component that changes with frequency d) and

having an amplitude of -c13, missing

when the rotating diodes of bridge 3 are in good order, and the second harmonic amplitude is halved to the value 0 L1.

J 7GK s

The ratio of the amplitudes of the first and second harmonics is 3/4, while

as with healthy diodes, despite the possible differences in their current-voltage characteristics, this ratio is close to zero.

In the same ratio changes and

the spectrum of the linear EMF of the three-phase winding 1 core of the main machine, the modules of which are chosen as the control signal, and the second harmonic of these

Emf

Exactly the same result is obtained when

breakdown of any of the diodes of the m-phase full-wave bridge 3.

The device that implements the method (Fig. 2), works as follows.

Linear EMFs of the winding 1 of the core of the main machine, having a space-time structure described by formula (4), are fed to the input of a three-phase full-wave rectifier 6 loaded from the direct current side to the resistor 7.

Rectifier 6 is inserted into the circuit of the device so that the voltage across the resistor 7 when turning the rotor of the machine

the absolute value of the OTNJT72 modulus changed to 3/2 of the maximum value of the phase EMF of the winding 1 core of the main machine.

The voltage drop across the resistor 7 through the filter capacitance, where the constant component of this voltage separates, is fed to the input of the electronic amplifier 9, which increases the amplitudes of all the variable components of the output signal of the filter 8.

The signal from the output of amplifier 9 is fed to the second filter 10, which passes only the second harmonic of the signal and transforms its amplitude into a proportional direct current voltage that goes further to the input of the comparator 11. The comparator 11 threshold is chosen 1.5 times smaller than the voltage at the output of the filter 10 when the rotating diodes are healthy, therefore when the diodes are working, the trigger 12, controlled by the comparator 11, is in such a state that the warning lamp 14 does not work.

When any of the rotating diodes is short-circuited and the rotor rotates appropriately, the voltage at the output of the filter 10 is halved, as the second harmonic level of the linear EMF of the winding 1 core of the main machine decreases twice, and the comparator 11 flips trigger 12, which is fixed in this state regardless of further rotation of the rotor and includes an alarm 14.

Trigger 12 returns to its initial position by push button 13.

The detection of the short circuit of a rotating diode, according to the method, can also be carried out by viewing the voltage across the resistor 7 on the screen of the electronic oscilloscope.

At some aircraft facilities (for example, the Yak-42 and An-72 aircraft), synchronous generators with gl-phase, full-wave rotary rectifiers are used. The generators are driven by the propulsion engines of the aircraft.

Since the existing technology of detecting the short circuits of rotating diodes of aviation synchronous generators requires the work of the cruise engine, the introduction of this method eliminates

Claims (1)

change in fuel and energy costs, since the implementation of the method does not require rotation of the generator. The invention of the method for detecting a short-circuit of a rotating diode of a gp-phase rectifier of a three-phase synchronous machine, comprising connecting one of the windings of the machine to a source of sinusoidal alternating voltage, creating the phases of the winding of a non-rotating core of an exciter of a three-phase synchronous machine of time-varying alternating currents, registration of the DS in a winding that is not connected to the source with a smooth turn the rotor and the detection of short circuits by the results of the comparison of the EMF with reference value, different so that in order to detect short of the rotating diode in a full-wave rectifier, the exciter excitation winding is connected to the source, the linear emf of the winding of the core of the three-phase synchronous machine is recorded with one complete rotation of the rotor, and as the reference takes the value of the second harmonic modulus of the indicated linear emf 1764000 V / Hi Fcg.1 B