SU1249636A1 - Device for determining the arcing level of brushes of electric machines - Google Patents

Abstract

The invention relates to electrical engineering, in particular to devices for diagnosing synchronous electric machines. The aim of the invention is to improve the accuracy of the determination of the spark level of the brushes. The device contains two conductors 5 with an alarm device 6, a driver 14 pulses, a diode 10 and a display unit. The device is equipped with two current. sensors 7, made in the form of a magnetic conductor with a winding and mounted on a single conductor. Between the sensors, one of the terminals of the shunt capacitor 8 is connected to the conductor, the other terminal of which is connected to another conductor. The windings of the current sensors are connected in opposite through the resonant amplifier 9, the diode and the integrator are connected to the first input of the switch 12, the second input of which is connected to the output of the pulse former 14, the input of which is connected to one of the conductors, and the output of the switch is connected to the display unit , 1 Il. CO Od with O) Li ... J sg Neither drove

Description

The invention relates to electrical engineering, in particular to diagnostic systems for synchronous electric machines,

The purpose of the invention is to improve accuracy by eliminating the signal that is not directly related to the malfunction of the brushes when determining the level of spark of brushes.

The drawing is a schematic diagram of the device.

The device contains a rotor 1 of a synchronous machine with excitation winding 2 and slip rings 3. Brushes 4 are connected to excitant device 6 by means of conductors 5. Two identical current sensors 7, made in the form of a magnetic winding, are installed on one of the conductors 5. The windings of the current sensors 7 are interconnected oppositely in a differential circuit. Between the current sensors 7, one of the terminals of the shunt capacitor 8 is connected to the specified current line, its other terminal is connected to another current line 5. The windings of the current sensors 7 through the resonant amplifier 9, diode 10, integrator 11 connected to the first input of the switch 12. One of the conductors 5 through the differentiating circuit 13 is connected to the input of the driver 14 pulses, the output of which is connected to the second input of the switch 12. The output of the switch 12 st Via a relay unit 15 with a display unit (not shown). In the circuit of the display unit entered the contacts of the electromagnetic relay 16 relay unit. The device also contains a power supply unit 17 connected to conductors 5.

The current sensor 7 is an annular ferrite magnetic core with a winding uniformly wound on the magnetic core. The conductor 5 passes through the window of the magnet tube of both sensors, connecting an exciter 6 with a brush 4. The parameters of the magnetic conductor are chosen from the condition of excluding its saturation at the maximum constant current of the excitation device 6,

The power supply of blocks 9, 14 and 15 is carried out from a parametric stabilizer, power supply block 17. Current sensors 7 and a shunt capacitor 8 are installed in the immediate vicinity of the brushes 4. The power supply unit 17 and the differentiation circuit 13 are connected to the conductors 5 in close proximity to the exciter 6, and the parameters of the differentiation circuit 13 are chosen so that they do not affect the circuit excitation frequency (i.e., the capacitance of the differentiating circuit 13 is significantly less than the capacitance of the shunt capacitor 8). The device works as follows.

Shunt capacitor 8 together with the inductance of the winding 2 of the rotor 1 forms a resonant circuit. The resonant frequency of the circuit is higher than the frequency of the network and higher harmonic in the voltage of the exciter 6. In the normal operation of the brush unit, when the brushes 4 are healthy and not sparks, there is no signal at the output of the current sensors 7, and regardless of whether there is a signal or not on the second input of the switch 12, the relay unit 15 does not work. When sparks appear on one of the brushes 4, a resonant circuit consisting of a shunt capacitor 8 and inductance of the winding 2 of the rotor 1 is excited. In the winding of the current sensor 7 located on the conductor 5 in the resonant circuit zone, an emf with a resonant frequency is induced contour. In the winding of the current sensor 7, located on the conductor 5 outside the resonant circuit, there is no EMF with a resonant frequency because there is no current in this circuit with a resonant frequency circuit. The emf induced in the windings of the current sensors 7 from the higher harmonic currents of the exciter device 6 is compensated for by means of the on-switching connection of the windings of the current sensors and the differential circuit. . .

The voltage from the windings of the current sensors 7 is supplied to the resistive amplifier 9, then detected by the diode 10, integrated by the integrator 11 and fed to the first input of the switch 12. The latter ensures that the DC signal passes to the relay unit 15 only if it has negative voltage input. The negative voltage to the second input of the switch 12 comes from the driver

14 impulses operating in standby mode. In standby mode, a negative voltage is present at the output of the drivers and the signal from the output of the integrator 11 is fed to the relay unit 15, causing the relay 16 to trip.

The pulse shaper 14 is triggered by pulses from differentiating circuit 13, which generates low-power pulses when the voltage of the exciter 6 appears. The positive pulse of the shaper 14 causes the switch 12 to be locked for a time equal to the pulse duration. The duration of the positive pulse at the output of the imaging unit 14 is chosen longer than the charging time of the resonant circuit (winding 2, capacitor 8).

Since modern exciters contain thyristor converters with phase voltage regulation, it is possible that voltage surges with steep fronts and shock excitation of the resonant circuit by these fronts are possible. These oscillations are suppressed by the switch 12, since the input of the relay unit

15 is closed for a time equal to the damping constant of the resonant circuit. In the absence of voltage jumps at the output of the excitation device 6, the switch 12 is constantly open and the signal from the integrator 11 is fed continuously to the input of the relay unit 15.

The differential switching circuit of the windings of the current sensors 7 provides for the compensation of all the EMF components, except for the EMF, which have a frequency of the resonant circuit. The resonant frequency of the circuit is chosen so that it does not coincide with the higher harmonic excitation current of the synchronous machine, and would not be a multiple of the mains frequency (as a rule, the frequency is more than 5 kHz).

The operation of the relay unit 15 monitors the state of the contacts of the electromagnetic relay 16 included in the circuit of the display unit of the controlled electric machine, ficNIIPI Order 4335/55 Circulation 597

Random polygons pr-tie, Uzhgorod, st. Project, 4

249636

Sir is the appropriate level of sparkle of the brushes.

The device also makes it possible to control the sparking of brushes that are not detectable visually, i.e. occurring in the body of the brushes.

In the proposed device, the accuracy of determining the level of arcing of the brushes is ensured, since 10 eliminates the fixation of signals, not

directly related to the disruption of the operation of brushes, for example, oscillations caused by voltage surges of the excitatory device in the normal mode of its operation, oscillations arising when the excitation is forced, in transient conditions.

Claims (1)

Invention Formula 20 A device for determining the spark level of brushes of electric machines, comprising a circuit for connecting to the brushes in the form of two conductors with an excitation device, a pulse shaper, a diode and an indication unit, characterized in that, in order to improve accuracy by eliminating the spark spark level signals that are not directly related to the malfunction of the brushes, two identical current sensors have been added to it ,. shunt condensate35 torus, resonant amplifier, integrator, switch, differentiating circuit and relay, unit, each of the current sensors is made in the form of a magnetic circuit with a winding and both g sensors are installed on the same current path, the first terminal of the shunt capacitor is connected to the current line between the sensors , the second terminal of which is connected to another conductor, the windings of current sensors are connected oppositely in a differential circuit and through a resonant amplifier, a diode and an integrator are connected to the first input of the switch, the second input otorrhea connected to the output of the pulse shaper, which is input through a differentiating circuit, connected to one of the conductors, and the switch output is coupled through a relay unit with a display unit. 45 50 Subscription