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INVENTION
Patent of the Russian Federation RU2288534
DEVICE FOR PUNCHING AND COMPENSATION OF REACTIVE POWER
ASYNCHRONOUS ENGINE
Applicant's name: State Educational Institution of Higher Professional Education "Ulyanovsk State Technical University" (RU)
The name of the inventor: Dmitriev Vladimir Nikolaevich (RU); Gorbachevsky Nikolay Ivanovich (RU)
The name of the patent holder: State Educational Establishment of Higher Professional Education "Ulyanovsk State Technical University" (RU)
Address for correspondence: 432027, Ulyanovsk, Severnyy Venets, 32, GOU VPO "Ulyanovsk State Technical University", pro-rector for scientific work
Date of commencement of the patent: 2005.07.08
The invention relates to electrical engineering and can be used for starting and compensating the reactive power of asynchronous electric motors of high power with fan load or unloaded. The device contains stator windings with series-connected capacitors, which are automatically connected in parallel to the stator windings during the start-up at a given transition point. The technical result consists in increasing the starting torque by increasing the supply voltage at the time of starting and increasing the reliability of the device by eliminating the danger of the self-excitation of the engine. The invention provides a limitation of the starting current during the start-up and compensation of the reactive power of the induction motor in the operating mode.
DESCRIPTION OF THE INVENTION
The invention relates to electrical engineering and can be used for starting and compensating the reactive power of asynchronous electric motors of high power with fan load or unloaded.
A device is known for starting and compensating the reactive power of an induction motor by sequentially switching capacitors to the stator windings, which remain connected in series and in the operating mode [ see Bauman, VG, Ivanov, OV, Komarov, VI. Self-excitation of induction motors with series capacitors // Electricity, 1961, №5. (Fig . 1) ]. The disadvantage of the known device is the danger of resonant phenomena in the operating mode.
A device is also known for starting and compensating the reactive power of an induction motor by sequentially switching capacitors to the stator windings, which after being started are shunted with keys [ see Petrov, II, Meistel, A.M. Special modes of operation of an asynchronous electric drive. M .: Energia, 1968, (Fig. 2-8, a) ]. The disadvantage of this device is the non-use of capacitors in the operating mode.
The device closest to the claimed invention is the device for starting and compensating the reactive power of an induction motor, comprising a three-phase switch whose terminals are connected to the ends of the stator windings, capacitors whose first terminals are connected to the ends of the stator windings, and the second terminals are connected to a point, And a manual switching device designed to switch the connection scheme of the stator windings from star to delta after start-up [ see Magyar L. Power factor (cos
).
ML: Gosenergoizdat, 1961 (рис.109) ].
The prototype and the claimed invention have the following similar essential features: a three-phase switch whose clamps are connected to the ends of the stator windings, capacitors whose first clamps are connected to the ends of the stator windings, and a switching device designed to switch the connection scheme of the stator windings and capacitors.
The disadvantage of the prototype is , firstly, a small starting torque, which is explained by the connection of the stator windings during the start-up to phase voltages, which reduces the starting torque by a factor of three in comparison with the inclusion of windings for line voltages. Secondly, the danger of resonant phenomena, because In connection with the short-time flow of the starting mode and the absence in the prototype of the automation system, it is practically impossible to provide a timely switching of the winding and capacitor circuit and, as a consequence, the occurrence of a self-excitation regime in the region of small slip.
The technical result is an increase in the starting torque by increasing the supply voltage at the time of starting and increasing the reliability of the device by eliminating the danger of the self-excitation of the engine.
To achieve the technical result, the claimed invention - a device for starting and compensating the reactive power of an induction motor - comprises a three-phase switch whose terminals are connected to the ends of the stator windings, the capacitors whose first terminals are connected to the ends of the stator windings, and a switching device intended for switching the winding connection Stator and capacitors, characterized in that the second terminals of the capacitors are connected to the ends of the stator windings and to the clamps of the switch, and the switching device is made in the form of a magnetic starter, the coil of which, together with the series-connected resistor, is connected in parallel to one of the stator windings, and the resistor is shunted by the contact of the magnetic starter , Other contacts of the magnetic starter are connected between the connection points of the ends of the stator windings and capacitors.
The essence of the invention is illustrated by a drawing, which shows an embodiment of the device for starting and compensating the reactive power of an induction motor.
The device contains a three-phase switch 1, whose terminals are connected to the ends of the stator windings 2, 3, 4, the capacitors 5, 6, 7, whose first terminals are connected to the ends of the stator windings 2, 3, 4, and the second terminals of the capacitors 5, 6, 7 are connected To the start of the stator windings 2, 3, 4 and to the terminals of the switch 1, a switching device for switching the connection circuit of the stator windings and capacitors in the form of a magnetic starter, the coil 8 of which together with the series-connected resistor 9 is connected in parallel to one of the stator windings 4 , The resistor 9 is shunted by the contact 10 of the magnetic starter, the other contacts 11 and 12 are connected between the connection points of the ends of the stator windings 2, 3, 4 and the capacitors 5, 6, 7.
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The device works as follows. To start the electric motor, the three-phase switch 1 is turned on, the capacitors 5, 6, 7 are turned on in series with the stator windings 2, 3, 4. The voltage applied to the stator windings 2, 3, 4 is reduced by the voltage drop across the capacitors 5, 6, 7, which, in turn, limits the starting current. As the engine speed increases, the voltage applied to the stator windings 2, 3, 4 increases, and when it reaches a certain value, the coil 8 of the magnetic starter trips. As a result, a resistor 9 is shunted by means of the contact 10, which increases the voltage on the coil 8 to a nominal value and ensures a reliable operation of the magnetic starter. In addition, closing the contact 10 eliminates the losses on the resistor 9 in the operating mode. At the same time, the contacts 11, 12 of the magnetic starter are closed, the capacitors 5, 6, 7 are switched in parallel with the stator windings 2, 3, 4 of the motor, ensuring compensation of the reactive power of the engine in the operating mode. |
As calculations and tests of the device have shown, the most favorable time for switching on the coil 8 is when the voltage at the stator windings 2, 3, 4 reaches the nominal value, which corresponds to the rated current in these windings. In this case, the transition of the engine to the operating mode occurs most smoothly. However, the coils of 8 serial magnetic starters have a trip voltage of 20-30% below the rated voltage. The setting of the resistor 9 can be achieved for each particular magnetic starter when its operation will occur when the nominal or other set voltage is reached.
In addition, as the tests have shown, the resistor 9 limits the ejection and current rolls in the coil 8 when it is turned off, excluding the re-inclusion of this coil in the region of low rotational frequencies.
Thus, the proposed device provides limitation of the starting current and compensation of the reactive power of the induction motor, while in comparison with the prototype it provides an increase in the starting torque due to an increase in the supply voltage at the time of starting and an increase in the reliability of the device due to elimination of the danger of the self-excitation of the engine.
CLAIM
A device for starting and compensating the reactive power of an induction motor, comprising a three-phase switch whose terminals are connected to the ends of the stator windings, capacitors whose first clamps are connected to the ends of the stator windings and a switching device for switching the stator winding and capacitor coupling circuit, characterized in that The second terminals of the capacitors are connected to the ends of the stator windings and to the clamps of the switch, and the switching device is made in the form of a magnetic starter, the coil of which, together with the series-connected resistor, is connected in parallel with one of the stator windings, and the resistor is shunted by the contact of the magnetic starter, the other contacts of the magnetic starter are connected between the points Connecting ends of stator windings and capacitors.
print version
Date of publication 03.12.2006гг
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