SU53178A1 - Device for driving machine guns - Google Patents

Description

The main author's certificate No. 42629 described a device for driving machine guns in rotation, made in the form of a segmented stator of a multiphase asynchronous motor, attached to a cylindrical part of a driven machine gun.

The present invention aims to make such a drive device very slow at a normal current frequency (50 hertz).

For this, according to the invention, capacitors are connected in series with the phases of a segmented stator that are made with an increased linear load, the capacitors of which are taken to be close to the inductive resistance of the stator winding.

In addition to this goal, this inclusion of capacitors in the segmented stator circuit makes it possible to obtain starting characteristics similar to the calculation of capacitors, starting characteristics of shunt or compound motors, and the possibility of reducing the starting current. At the same time, capacitors increase the net power factor.

The invention is illustrated in the drawing, in which FIG. 1-3 depict various possible capacitor switching circuits, and FIG. 4-7 vector diagrams.

In series with the phase windings of the stator of the proposed device, capacitors C are included, the capacitance resistances of which are selected according to the calculation given below. R denotes the squirrel cage rotor.

Depending on the conditions, capacitors C can be installed both on the stator itself and outside of it, for example, on the floor, behind the switchboard next to the machine switch.

The mode of operation of the machine when using capacitors will differ significantly from the mode of operation of a conventional asynchronous machine, especially during start-up. These differences are derived from the vector diagrams, of which FIG. 4 refers to a conventional asynchronous machine, and FIG. 5-7- to the proposed drive.

The diagrams have the following notation:

i-phase network voltage, 4 s capacitive, i.e. negative voltage drop in a properly selected capacitor,

/./ 1-Ohmic voltage drop in the stator winding, - inductive voltage drop in the stator winding (or on a different scale, the stator scatter flow). The vector f / j is the voltage at the stator terminals, and the vector E is at a certain scale the useful magnetic flux, i.e. the flux entering the rotor of the machine.

From the diagram of FIG. 5, it can be seen that the capacitor makes it possible to counteract sudden decreases in the magnetic flux in the gap. There are two possible cases. One of them is the case of the so-called voltage resonance, when

  l. ()

Where:

X is the capacitive reactance of a capacitor (in ohms),

w - circular frequency of the supply current, numerically equal to its usual frequency, increased 27c times,

 - reactive inductive resistance of the stator winding of the machine (in ohms), LI - self-induction of the stator winding

(in henry)

С - capacitor capacitance (in farad).

In this case, the inductive impedance of the stator will be fully balanced by the capacitive and the top of the useful magnetic flux vector will move, as the machine accelerates, within narrow limits from S to L (Fig. 5), i.e., the magnitude of the change of the useful magnetic flux of the stator from a point short closure to the point of idling will be negligible. As a result, we get

start-up and all subsequent transient modes to Normal almost at full, and not at sharply reduced useful magnetic flux of the machine.

The ROLE and the value of the capacitor corresponding to equation (1) and coupled to the stator of the machine according to the scheme of FIG. 3 is that such a capacitor makes the starting characteristics of the machine physically identical to the starting characteristics of the shunt electric motor, where the start-up takes place, as is well known, also with full, and not with, reduced excitation magnetic flux.

By decreasing capacitance C, one can further achieve such capacitance values X

to “From time to time the condition

.X

(2)

1f

In the diagram of FIG. b this case is presented. We then get the start-up of the machine, not only with full, but even with increased against the nominal magnetic flux. The latter in this case will decrease from -B to L, and not increase as the car accelerates.

The role and value of the capacitor with the capacitance in question is that the starting characteristics of the machine make such a capacitor identical to the starting characteristics of the com- puter electric motor (with a magnetising serial winding), where the start-up takes place, as is well known, also with increased, but not with constant or reduced magnetic flux in the gap.

Thus, conditions (1) and (2) determine for capacitors their capacitance, which is necessary to eliminate the drops in the useful magnetic flux of the machine.

However, not every stator can combine a capacitor that meets conditions (1) and (2).

If the additional condition regarding the stator and rotor resistances is not complied with, during the start-up such a powerful starting moment and so large a multiplicity of starting current can be obtained.

end with the destruction of even the most durable elements of the electric drive.

Therefore, with capacitors that meet conditions (1) and (2) can be connected as shown in FIG. 3 are not asynchronous machines in general, but such machines, where the ohmic resistance of the stator, as well as the reduced resistance of the rotor, are correspondingly increased, but of all the possibilities that are available to obtain such increased resistances, the increase in the phase number of the stator turns W is more efficient and effective, since the resistance of the rotor increases in proportion to the square of the increase in W.

Equally sharply (square function) decreases with increasing W, the capacitor capacitance is necessary, since the inductive resistance of the stator, balanced by the capacitance of the capacitor, is proportional to W.

In the absence of saturations in the magnetic circuit, the magnetizing current decreases in proportion to the square of the increase in W.

Such a sharp decrease in the magnetizing current while maintaining the capacitor at the maximum level of magnetic flux and the starting torque solves the fundamental problem - to make asynchronous machines at very low speeds at a frequency of 50 Hz.

An increase in the linear load AS of the stator, proportional (while maintaining the diameter of the machine) to an increase in the phase number of turns, creates prerequisites for very intensive use of the active surface of the machine, i.e., reducing the length (axial size) of the machine, reducing, in this respect, clearance heat transfer through the frontal parts.

When series capacitors are switched on in the stator circuit, induction machines get the starting characteristics of shunt and compound DC motors with all the ensuing consequences — this is the most important feature of such switching. The essential value of the present proposal lies further in the fact that the combination of very effective new capabilities is achieved for asynchronous machines not by mechanisms with complex combinations of a large number of various structural units and parts, but by a combination of the simplest static apparatus — a capacitor with an arc stator deliberately designed with significantly increased using an active surface by increasing the linear load.

In conclusion, it should be emphasized that in combination with capacitors according to the scheme of FIG. 3 and, by condition (2), many types of mid-range and high-speed asynchronous machines of capacities and voltages, and especially large capacities and high voltages, can be very progressively modernized.

This upgrade mainly consists of the following:

Claims (4)

1. A drastic decrease in the frequency of short-circuit currents and the achievement of starting characteristics identical to those of starting DC compound motors. 2. Significant improvement in cos - up to the leading ones in some high-speed types of machines. 3. Reducing the weight of machines. Indeed, imagine a powerful high-speed asynchronous electric motor. In such an electric motor, the stator and rotor reactants are small, and the short circuit multiplicity is large. Now we turn on according to the scheme of FIG. 3 in the stator so significant capacitive impedance, which would be greater than the double reactant dissipated the entire machine. By this, the short-circuit current 1 can be reduced as much as desired, but at the same time in this case the useful magnetic flux of the electric motor will not be reduced at all, but on the contrary, it will be even higher at start-up than at the nominal mode (Fig. 7). An asynchronous motor therefore acquires the starting characteristics of a compound motor. Impacts or sharp mechanical stator windings during start-up will practically be excluded. From the diagram of FIG. 7 it is also clear that with proper selection of capacitance of a capacitor, we get a nominal cos of an electric motor equal to 1 or, say, 0.95 ahead. In this case, the capacitance of the required capacitor is especially small, since the capacitance must be so large that it more than doubles to compensate for the dissipation of the entire machine. The subject matter of the invention. 1. The form of the device according to claim 1 of copyright certificate No. 42629, characterized in that, in order to carry out at low frequency very low speed drives, the phase of the segment stator, performed with increased linear load, are connected in series with capacitors, capacitance which is close to the inductive resistance of the stator winding. 2. The form of the device according to claim 1, characterized in that, in order to obtain starting characteristics from the electric drive, identical to the starting characteristics of the shunt electric motor, the capacitance of the capacitors is equal to the inductive resistance of the winding of the segment stator. 3. The form of the device according to claim 1, characterized in that, in order to obtain starting characteristics from the electric drive that are identical to the starting characteristics of the compound motor, the capacitance resistance of the capacitors is greater than the inductive resistance of the stator winding. 4. The form of the device according to claim 3, characterized in that, in order to reduce the inrush current and at the same time obtain a compound characteristic from the drive, the resistance of the capacitors is greater than the double reactor value of the entire drive device. S - with - isishishvn - tashon Ishkhuch 2 shui --Sh5Sh) FIG. five shhh Ш5Ш5