SU1000951A1 - Dc electric motor checking device - Google Patents

Description

(54) DC ELECTRIC MOTOR CONTROL DEVICE

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The invention relates to electric machines of predominantly low power and can be used in specialized diagnostics devices for the in-place assessment of the technical condition of electric motors of various objects, for example, airplanes, as well as in electrical engineering.

A device for controlling electrical machines is known, which contains a built-in switch for switching voltage pulsations, a filter and an indicator 1.

A disadvantage of the known device is the limited field of application, due to the use of the built-in 15 sensor switching voltage pulsations and the dependence of the monitored parameter on the mode of operation of the machine.

It is also known to control electrical machines, which contains a measuring transducer of the average value of voltage pulsations, an amplitude limiter and an indicator i2,

The disadvantages of the known device also include the limited field of application, due to the fact that the device in question, when being monitored, requires connection directly to the machine's brushes. Such a requirement for many machines (especially low power) is impossible without their partial development: assembly. In addition, the indicator readings also depend on the mode of operation of the Machine, which makes it impossible to monitor most electric cars directly at the facility, for example, on board an aircraft.

The closest in technical essence and the achieved result to the proposed is a device containing a switching voltage pulsation sensor with two primary windings,. shunt capacitor, measuring unit, ratio of peak and average voltage values of voltage ripples, rotational frequency control unit Q. The disadvantages of the known device are limited accuracy and considerable weight and size, due to the low ratio of the operating frequency of the shunt capacitor and the compensation winding with a limited mass and size characteristics of the portable control device in practice. is impossible. The purpose of the invention is to improve the accuracy and improve the mass and size xapaKTe pattern. This goal is achieved by providing the device with a diode bridge, a source of sinusoidal voltage and a coupling capacitor, and the transformer is made in the form of two cores, each of which is wound with a primary and secondary windings ,. the primary windings are connected according to, the secondary windings are connected in opposite direction, the source of sinusoidal voltage and one diagonal of the diode bridge are connected in series with the secondary windings, and the second diagonal of the diode ma: t through (separator, capacitor is connected to the inputs of the peak ratio and average sensor) values of voltage pulsations and control of rotation frequency. In Fig. 1, the diagram of the proposed device is shown; Fig. 2 shows the curves of magnetic fluxes F and F2 in a transform and then a direct current, Secondary current illograms. The device contains a current transformer with two cores, on which primary 1 and 2 and secondary 3 and 4 windings are wound, a diode bridge 5, separation capacitor 6, sources of sinusoidal voltage 7, meter 8 for peak and foreground pulsation values voltage, block 9 frequency control. The device operates as follows: When the motor is connected to a power source through windings I and 2 (Fig. I) direct current will flow and in the absence of alternating current in the secondary windings the flow in one of the HKkoB cores will be + Fe, and in the second ® ° core will be saturated. Consequently, a change in flux at any cores is possible only n ctovioHy u1e1 of the absolute value) 1HT1 ppt (k / 1, i.e., the change of the core flux under the action of the EMF variable can be represented only as a subtraction of the constant flux. The process of flux change is shown in Fig. 2. Such a subtraction of flux in the core can occur only during the half period when the field strength created by the variable component of the current has a negative value with respect to the voltage the field created by the primary - direct current. The resulting magnetic creeps created by the currents and 3 y in the core, in which the induction varies, is 0 | 4ft,., H HQ-H - (,), where 3i is the current in the primary - current in secondary windings. With an ideal magnetization curve, the flux can change and take values less than the saturation flux if the resulting field strength H0, i.e., the variable field component of the current H - compensates the DC field HQ, Therefore, for that core, whose induction from ene is, to have only a semi-Heat-i 00 I ZmOOts. Due to the fact that during one half cycle the flow in one of the cores remains unchanged, the inductive resistance of the winding of this core during the specified half period is zero, and the current in the secondary winding from the auxiliary source of alternating voltage is determined solely by the inductive resistance of the winding of the second core, where the magnetic flux in this half-period is changing. During the other half cycle, the windings change roles. FIG. 2-1 shows an alternating current diagram of -t, which, with an ideal Magnetization curve and the absence of a current of twice the frequency, which is achieved by including an inductance in the control circuit or selecting a small number of turns for the CDu winding, is rectangular, despite the fact that the supply voltage has a sinusoidal shape. After straightening with a diode bridge, we obtain a constant load current t) c ((, shown in Fig. 2 °). For this current, we have I H JH IH IM

This formula is valid not only for medium or acting, but also for instantaneous currents. This means that all changes in the primary current (ripple, the presence of a variable component, increase and decrease associated with the transient mode in the primary circuit) will be reproduced in the secondary circuit. To separate the pulsations from the received signal, an isolating capacitor 6 is inserted at the input (Fig. 1).

The use of the proposed device in comparison with the known ones results in higher reliability due to an increase in the accuracy of measurement of current ripple (voltage). This is due to the fact that in the proposed device, current pulsations are transformed (from an electric motor circuit) to the input of the measuring units with almost no distortion and in a wide frequency range, which is not the case in the known devices. In addition, in order to reduce distortions of the transmitted spectrum, especially in the low-frequency region, the capacitance and inductance in the pulsation sensor of the device should be as large as possible, i.e., the weight and size characteristics increase significantly. Since, as a rule, the controlled motor is powered by a special power supply unit (with a low level of pulsations) containing a power step-down voltage transformer, it is advisable to use one of the secondary windings of the specified transformer as a source of sinusoidal voltage. This practically makes it possible to reduce the mass and volume of the switching voltage pulsation sensor by a factor of 2–5 (depending on the value of the lower frequency of the ripple spectrum).

In turn, the improvement of the mass-size characteristics of the device provides a reduction in material costs and

makes the process of its use (for example, when used as a portable device), more convenient to operate.

Claims (3)

1. Authors certificate of the USSR N 131821, cl. H O2 K 15/00, 1956. 2. Plus BM and others. On the measurement of the intensity of arcing in DC machines. Izv. higher studies, institutions. Electromechanics, 1969, No. 4, p. Zb539O. 3. USSR author's certificate in application N 3005777/24-О7, cl. H P2-K 1-5 / 00, 1980. 4w five one -C -H uh