RU2461118C1 - Single-phase network-driven frequency speed regulator for three-phase asynchronous short-circuited electric motor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: single-phase network-driven frequency speed regulator for a three-phase asynchronous short-circuited electric motor belongs to devices for launch and regulation of speed of three-phase asynchronous electric motors in case of power supply from single-phase network and is intended for usage in an electric drive for control of speed of three-phase asynchronous electric motors stator windings whereof are delta-connected. Each of the three reverse semiconductor commutators of the device contains two oppositely connected transistors intended for power supply of the electric motor stator windings in case of the windings delta-connection.

EFFECT: provision for the possibility to perform regulation of the electric motor rotation speed both over and below the rated speed, mean torque increase and energy performance improvement.

6 dwg

Description

The invention relates to devices for starting and controlling the speed of three-phase asynchronous electric motors powered by a single-phase network and can be used in an electric drive to control the speed of asynchronous three-phase electric motors, the stator windings of which are connected according to the "triangle" scheme.

A device for the capacitor start of a three-phase electric motor from a single-phase network, containing a paper capacitor and inductance. The capacitor and inductance have a common output, which is designed to connect to the outputs of the windings, one of which is connected to the zero of the single-phase network, and the other is connected to the phase of the single-phase network. The other output of the capacitor is connected to the phase of the single-phase network and is designed to connect to the outputs of the windings, one of which is connected to the zero of the single-phase network. The other inductance output is connected to the zero of the single-phase network and the outputs of the windings, one of which is connected to the phase of the single-phase network. The motor windings are connected in the form of a "triangle" (S. Biryukov. Three phases - without loss of power / S. Biryukov // Radio. - M., 2000. - No. 7. - P.37, Fig. 1).

The main disadvantages of the described device for the capacitor starting of a three-phase electric motor from a single-phase network are the lack of speed adjustment, increased dimensions, due to the need to use paper capacitors of large capacity and inductances, as well as low reliability due to the presence of capacitors and inductors in the circuit.

The closest to the proposed invention in technical essence and the achieved result (prototype) is a semiconductor device for non-capacitor starting a three-phase electric motor from a single-phase network, containing two reversing semiconductor switches, each of which contains two counter-parallel connected transistors, designed to power the stator motor windings when connected stator windings according to the "triangle" scheme. In the first reversible semiconductor switch, the collector of the first transistor is connected to the emitter of the second transistor, and their common output is for connecting to the phase of the supply network, the emitter of the first transistor is connected to the collector of the second transistor, and their common output is for connecting to the common output of the first and second stator windings . Thus, one of the common terminals of the first and second transistors is intended to be connected to the common terminal of the first and second stator windings. In the second reversible semiconductor switch, the collector of the third transistor is connected to the emitter of the fourth transistor, and their common output is for connecting to the phase of the supply network, and the emitter of the third transistor is connected to the collector of the fourth transistor, and their common output is for connecting to the common output of the second and third stator windings. Thus, one of the common conclusions of the third and fourth transistors is designed to connect with the common output of the second and third stator windings. The common output of the first and second stator windings is connected to zero single-phase network (patent RU 2385527, IPC Н02Р 1/26 (2006.01), Н02М 5/257 (2006.01)).

The main disadvantages of this semiconductor device for capacitor-free starting of a three-phase electric motor from a single-phase network are the inability to control the frequency of rotation of the electric motor, low average torque and reduced energy performance due to the elliptical shape of the stator electromagnetic field.

The present invention solves the problem of adjusting the frequency of rotation of the electric motor, increasing the average moment and increasing energy performance.

To solve the problem, a single-phase frequency governor driven by a network for a three-phase asynchronous squirrel-cage motor, equipped with reversible semiconductor switches, each of which contains two connected transistors, designed to power the stator windings of the motor when connecting the stator windings according to the "triangle" circuit, with a common output the first and second transistors of the first reversing semiconductor switch is designed to connect to a common output of the first th and second stator windings, and the common terminal of the third and fourth transistors of the second reversing semiconductor switch is designed to connect to the common terminal of the second and third stator windings, according to the invention is equipped with a third reversing semiconductor switch, in which the collector of the fifth transistor is designed to connect to the phase of the supply network, the collector of the sixth transistor is connected to zero single-phase network, the emitter of the fifth transistor is connected to the emitter of the sixth transistor, and their common output is pre Designed to connect with the common output of the first and third stator windings. Moreover, in the first reversible semiconductor switch, the collector of the first transistor is designed to connect to the phase of the supply network, the collector of the second transistor is connected to zero single-phase network, the emitter of the first transistor is connected to the emitter of the second transistor, and their common output is used to connect to the common output of the first and second stator windings, and in the second reverse semiconductor switch, the collector of the third transistor is designed to connect to the phase of the supply network, the collector of the fourth trans ora connected to the zero-phase network, the emitter of the third transistor is connected to the emitter of the fourth transistor, and a common output for connection to the common terminal of the second and third stator windings. The transistors of each reversible semiconductor switch are connected in the opposite direction.

The ability to control the rotational speed of the electric motor, increase the energy performance, as well as increase the average moment are caused by a change in the circuit of reversing semiconductor switches by introducing a third reversing semiconductor switch, using the ability of semiconductor transistors in the key mode to pass current in the opposite direction due to the symmetrical structure of the semiconductor transistor (pnp or npn), as well as the inclusion of transistors in the semiconductor switch is opposed, but not parallel.

The invention is illustrated by drawings, where Fig. 1 is a circuit diagram of a proposed single-phase frequency governor driven by a network for a three-phase asynchronous squirrel-cage motor; figure 2 shows a vector diagram of the rotation of the magnetic field of the stator, consisting of six fixed positions of the magnetic flux of the stator; figure 3 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2, to obtain the calculated frequency of 50 Hz; figure 4 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2, to obtain the calculated frequency of 33.33 Hz; figure 5 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2, to obtain the calculated frequency of 25 Hz; figure 6 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2, to obtain the calculated frequency of 100 Hz.

In addition, the following notation is used in the drawing:

- f - phase;

- 0 - zero;

- A, B, C - stator windings of the electric motor;

- I, II, III, IV, V, VI - consecutive fixed positions of the magnetic flux vector of a circular rotating field of the stator of an induction motor;

- t1, t2 ... t13 - moments of time switching transistors;

- U-networks - mains voltage;

- Ua, Uv, Uc - voltage across the stator windings A, B and C, respectively;

- Ia, Iv, Ic - current in the stator windings A, B and C, respectively;

- short arrows-vectors - a phased change in the direction of the resulting magnetic field of the stator;

- arcuate lines with an arrow - the direction of rotation of the stator magnetic field;

- long solid arrows - the direct direction of the current in the stator windings of the electric motor;

- long discrete arrows - the reverse direction of the current in the stator windings of the electric motor.

The single-phase frequency governor driven by the network for a three-phase asynchronous squirrel-cage motor is equipped with three reversible semiconductor switches, each of which contains two counter-connected transistors designed to power the stator windings of the motor when connecting the stator windings according to the "triangle" scheme. In the first reversible semiconductor switch, the collector of the first transistor 1 (VT1) is designed to connect to the phase of the supply network, the collector of the second transistor 2 (VT2) is connected to zero single-phase network, the emitter of the first transistor 1 (VT1) is connected to the emitter of the second transistor 2 (VT2), and their common output is intended to be connected to the common output of the first and second stator windings 3 (winding A) and 4 (winding B), respectively. In the second reverse semiconductor switch, the collector of the third transistor 5 (VT3) is designed to connect to the phase of the supply network, the collector of the fourth transistor 6 (VT4) is connected to zero single-phase network, the emitter of the third transistor 5 (VT3) is connected to the emitter of the fourth transistor 6 (VT4), and their common output is intended to be connected to the common output of the second and third stator windings 4 (winding B) and 7 (winding C). In the third reversible semiconductor switch, the collector of the fifth transistor 8 (VT5) is designed to connect to the phase of the supply network, the collector of the sixth transistor 9 (VT6) is connected to zero single-phase network, the emitter of the fifth transistor 8 (VT5) is connected to the emitter of the sixth transistor 9 (VT6), and their common output is intended to be connected to the common output of the first and third stator windings 3 (winding A) and 7 (winding C), respectively. The transistors of each reversible semiconductor switch are connected in the opposite direction. In the first reversing semiconductor switch, the emitter of the first transistor 1 (VT1) is connected to the emitter of the second transistor 2 (VT2), in the second reversing semiconductor switch the emitter of the third transistor 5 (VT3) is connected to the emitter of the fourth transistor 6 (VT4), in the third reversing semiconductor switch emitter the fifth transistor 8 (VT5) is connected to the emitter of the sixth transistor 9 (VT6).

The operation of a single-phase frequency governor driven by the network for a three-phase asynchronous squirrel-cage motor is as follows. To obtain the calculated frequency of 50 Hz, when the positive half-wave of the supply voltage U of the network passes (Fig. 3), at the initial moment of time, the third transistor 5 (VT3) and the sixth transistor 9 (VT6) (Fig. 1) open, the current goes through three windings 7 (winding C), 4 (winding B), 3 (winding A) of the electric motor, we take this direction of current in the windings as positive. The voltage on the winding C (Fig. 3) is equal to the phase U network; on the windings A and B, the voltage is equal to U network / 2, respectively. Formed the first position of the vector of the magnetic field of the stator (figure 2). At time t1, the sixth transistor 9 (VT6) closes, the second transistor 2 (VT2) opens, the third transistor 5 (VT3) remains open and the current goes through the three windings 4 (winding B), 7 (winding C), 3 (winding A ) electric motor. The second position of the stator magnetic field vector is formed. At time t2, the third transistor 5 (VT3) closes, the fifth transistor 8 (VT5) opens, the second transistor 2 (VT2) remains open and the current goes through the three windings 3 (winding A), 7 (winding C), 4 (winding B ) electric motor. A third position of the stator magnetic field vector is formed. When the negative half-wave of the supply voltage passes (time t3), the fifth transistor 8 (VT5) and the second transistor 2 (VT2) close and the sixth transistor 9 (VT6) and the third transistor 5 (VT3) open and the current goes through three windings 7 (winding C ), 3 (winding A), 4 (winding B) of the electric motor. The fourth position of the stator magnetic field vector is formed. At time t4, the sixth transistor 9 (VT6) closes and the second transistor 2 (VT2) opens, the third transistor 5 (VT3) remains open and the current goes through the three windings 4 (winding B), 3 (winding A), 7 (winding C ) electric motor. The fifth position of the stator magnetic field vector is formed. At time t5, the third transistor 5 (VT3) closes and the fifth transistor 8 (VT5) opens, the second transistor 2 (VT2) remains open and the current goes through the three windings 3 (winding A), 4 (winding B), 7 (winding C ) electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. With the passage of the next positive wave (time t6-t7), the cycle repeats.

To obtain the calculated frequency of 33.33 Hz, when the positive half-wave of the supply voltage (Fig. 4) passes, at the initial instant of time t0, the third transistor 5 (VT3) and the sixth transistor 9 (VT6) open, the current goes through three windings 7 (winding C ), 4 (winding B), 3 (winding A) of the electric motor. The voltage on winding 7 (winding C) is equal to the phase U network, on the windings A and B, the voltage is equal to U network / 2, respectively. Formed the first position of the vector of the magnetic field of the stator (figure 2). At time t1, the sixth transistor 9 (VT6) closes, the second transistor 2 (VT2) opens, the third transistor 5 (VT3) remains open and the current goes through the three windings 4 (winding B), 7 (winding C), 3 (winding A ) electric motor. The second position of the stator magnetic field vector is formed. When the negative half-wave of the supply voltage passes (time t2), the third transistor 5 (VT3) and the second transistor 2 (VT2) close, the sixth transistor 9 (VT6) and the first transistor 1 (VT1) open, the current will go through three windings 3 (winding A ), 7 (winding C), 4 (winding B) of the electric motor. A third position of the stator magnetic field vector is formed. At time t3, the first transistor 1 (VT1) closes and the third transistor 5 (VT3) opens, the sixth transistor 9 (VT6) remains open and the current goes through three windings 7 (winding C), 3 (winding A), 4 (winding B ) electric motor. The fourth position of the stator magnetic field vector is formed. With the passage of the next positive half-wave of the supply voltage (time t4), the sixth transistor 9 (VT6) and the third transistor 5 (VT3) are closed and the first transistor 1 (VT1) and the fourth transistor 6 (VT4) open and the current goes through three windings 4 (winding B), 3 (winding A), 7 (winding C) of the electric motor. The fifth position of the stator magnetic field vector is formed. At time t5, the fourth transistor 6 (VT4) closes and the sixth transistor 9 (VT6) opens, the first transistor 1 (VT1) remains open and the current goes through three windings 3 (winding A), 4 (winding B), 7 (winding C ) electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. With the passage of the next negative half-wave of the supply voltage (time t6), the sixth transistor 9 (VT6) and the first transistor 1 (VT1) close, the fifth transistor 8 (VT5) and the fourth transistor 6 (VT4) open, the current goes through three windings 7 (winding C), 4 (winding B), 3 (winding A) of the electric motor. The first position of the stator magnetic field vector is formed. At time t7, the fifth transistor 8 (VT5) closes and the first transistor 1 (VT1) opens, the fourth transistor 6 (VT4) remains open and the current goes through three windings 4 (winding B), 7 (winding C), 3 (winding A ) electric motor. The second position of the stator magnetic field vector is formed. When the positive half-wave of the supply voltage (time t8) passes, the first transistors 1 (VT1) and the fourth transistor 6 (VT4) close and open the fifth transistor 8 (VT5) and the second transistor 2 (VT2) and the current will go through three windings 3 (winding A ), 7 (winding C), 4 (winding B) of the electric motor. A third position of the stator magnetic field vector is formed. At time t9, the second transistor 2 (VT2) closes and the fourth transistor 6 (VT4) opens, the fifth transistor 8 (VT5) remains open and the current goes through the three windings 7 (winding C), 3 (winding A), 4 (winding B ) electric motor. The fourth position of the stator magnetic field vector is formed. When the negative half-wave of the supply voltage passes (time t10), the fifth transistor 8 (VT5) and the fourth transistor 6 (VT4) close, the second transistor 2 (VT2) and the third transistor 5 (VT3) open, the current will go through three windings 4 (winding B ), 3 (winding A), 7 (winding C) of the electric motor. The fifth position of the stator magnetic field vector is formed. At time t11, the third transistor 5 (VT3) closes and the fifth transistor 8 (VT5) opens, the second transistor 2 (VT2) remains open and the current goes through the three windings 3 (winding A), 4 (winding B), 7 (winding C ) electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. With the passage of the next wave of supply voltage (time interval t12-t13), the operation algorithm is repeated.

To obtain the calculated frequency of 16.67 Hz (Fig. 5), when the positive half-wave of the supply voltage passes, at the initial time t0, the third transistor 5 (VT3) and the sixth transistor 9 (VT6) open, the current goes through three windings 7 (winding C ), 4 (winding B), 3 (winding A) of the electric motor. The voltage on the winding C is equal to the phase U network, on the windings A and B, the voltage is equal to U network / 2, respectively. Formed the first position of the vector of the magnetic field of the stator (figure 2). When the negative half-wave of the supply voltage (time t1) passes, the sixth transistor 9 (VT6) and the third transistor 5 (VT3) close, the fourth transistor 6 (VT4) and the first transistor 1 (VT1) open and the current goes through three windings 4 (winding B ), 7 (winding C), 3 (winding A) of the electric motor. The second position of the stator magnetic field vector is formed. With the passage of the next positive half-wave of the supply voltage (time t2), the fourth transistor 6 (VT4) and the first transistor 1 (VT1) close, the fifth transistor 8 (VT5) and the second transistor 2 (VT2) open, the current goes through three windings 3 (winding A), 7 (winding C), 4 (winding B) of the electric motor. A third position of the stator magnetic field vector is formed. When the next negative half-wave of the supply voltage passes (time t3), the fifth transistor 8 (VT5) and the second transistor 2 (VT2) close, the sixth transistor 9 (VT6) and the third transistor 5 (VT3) open and the current goes through three windings 7 (winding C), 3 (winding A), 4 (winding B) of the electric motor. The fourth position of the stator magnetic field vector is formed. When the positive half-wave of the supply voltage (time t4) passes, the sixth transistor 9 (VT6) and the third transistor 5 (VT3) are closed and the first transistor 1 (VT1) and the fourth transistor 6 (VT4) open and the current goes through three windings 4 (winding B ), 3 (winding A), 7 (winding C) of the electric motor. The fifth position of the stator magnetic field vector is formed. When the negative half-wave of the supply voltage passes (time t5), the first transistor 1 (VT1) and the fourth transistor 6 (VT4) close, the second transistor 2 (VT2) and the fifth transistor 8 (VT5) open and the current goes through three windings 3 (winding A ), 4 (winding B), 7 (winding C) of the electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. With the passage of the next wave (time interval t6-t7), the cycle repeats.

To obtain the calculated frequency of 100 Hz (Fig.6), when the positive half-wave of the supply voltage passes, at the initial instant of time t0, the third transistor 5 (VT3) and the sixth transistor 9 (VT6) open, the current goes through three windings 7 (winding C), 4 (winding B), 3 (winding A) of the electric motor. The voltage on the winding C is equal to the phase U network, on the windings A and B, the voltage is equal to U network / 2, respectively. Formed the first position of the vector of the magnetic field of the stator (figure 2). At time t1, after the sixth transistor 9 (VT6) is closed, the second transistor 2 (VT2) opens, the third transistor 5 (VT3) remains open and the current goes through the three windings 4 (winding B), 7 (winding C), 3 (winding A ) electric motor. The second position of the stator magnetic field vector is formed. At time t2, the third transistor 5 (VT3) closes, the fifth transistor 8 (VT5) opens, the second transistor 2 (VT2) remains open and the current goes through the three windings 3 (winding A), 7 (winding C), 4 (winding B ) electric motor. A third position of the stator magnetic field vector is formed. At time t3, the second transistor 2 (VT2) closes and the fourth transistor 6 (VT4) opens, the fifth transistor 8 (VT5) remains open and the current goes through the three windings 7 (winding C), 3 (winding A), 4 (winding B ) electric motor. The fourth position of the stator magnetic field vector is formed. At time t4, the fifth transistor 8 (VT5) closes and the first transistor 1 (VT1) opens, the fourth transistor 6 (VT4) remains open and the current goes through three windings 4 (winding B), 3 (winding A), 7 (winding C ) electric motor. The fifth position of the stator magnetic field vector is formed. At time t5, the fourth transistor 6 (VT4) closes and the sixth transistor 9 (VT6) opens, the first transistor 1 (VT1) remains open and the current goes through three windings 3 (winding A), 4 (winding B), 7 (winding C ) electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. When the negative half-wave of the supply voltage passes at time t6, the fifth transistor 8 (VT5) and the fourth transistor 6 (VT4) open, the current goes through three windings 7 (winding C), 4 (winding B), 3 (winding A) of the electric motor. The voltage on the winding C is equal to the phase U network, on the windings A and B, the voltage is equal to U network / 2, respectively. Formed the first position of the vector of the magnetic field of the stator (figure 2). At time t7, after closing the fifth transistor 8 (VT5), the first transistor 1 (VT1) opens, the fourth transistor 6 (VT4) remains open and the current goes through three windings 4 (winding B), 7 (winding C), 3 (winding A ) electric motor. The second position of the stator magnetic field vector is formed. At time t8, the fourth transistor 6 (VT4) closes, the sixth transistor 9 (VT6) opens, the first transistor 1 (VT1) remains open and the current goes through three windings 3 (winding A), 7 (winding C), 4 (winding B ) electric motor. A third position of the stator magnetic field vector is formed. At time t9, the first transistor 1 (VT1) closes and the third transistor 5 (VT3) opens, the sixth transistor 9 (VT6) remains open and the current goes through three windings 7 (winding C), 3 (winding A), 4 (winding B ) electric motor. The fourth position of the stator magnetic field vector is formed. At time t10, the sixth transistor 9 (VT6) closes and the second transistor 2 (VT2) opens, the third transistor 5 (VT3) remains open and the current goes through three windings 4 (winding B), 3 (winding A), 7 (winding C ) electric motor. The fifth position of the stator magnetic field vector is formed. At time t11, the third transistor 5 (VT3) closes and the fifth transistor 8 (VT5) opens, the second transistor 2 (VT2) remains open and the current goes through three windings 3 (winding A), 4 (winding B), 7 (winding C ) electric motor. The sixth position of the stator magnetic field vector is formed. The stator field is circular in time. When the next wave passes (time interval t12-t13), the operation cycle is repeated.

Thus, based on the foregoing, it can be concluded that the present invention has advantages over the known ones because of the possibility of adjusting the speed of the electric motor both above and below the nominal, higher average torque value, as well as increased energy performance.

Claims (1)

A single-phase frequency governor driven by a network for a three-phase asynchronous squirrel-cage motor, equipped with reversible semiconductor switches, each of which contains two connected transistors designed to power the stator windings of the motor when connecting the stator windings according to the "triangle" circuit, with the common output of the first and second transistors the first reversible semiconductor switch is designed to connect to the common output of the first and second stator windings, and about The output terminal of the third and fourth transistors of the second reversing semiconductor switch is designed to connect to the common terminal of the second and third stator windings, characterized in that it is equipped with a third reversing semiconductor switch, in which the collector of the fifth transistor is designed to connect to the phase of the supply network, the collector of the sixth transistor is connected to zero of a single-phase network, the emitter of the fifth transistor is connected to the emitter of the sixth transistor, and their common output is designed to connect with by the output of the first and third stator windings, while in the first reversing semiconductor switch, the collector of the first transistor is designed to connect to the phase of the supply network, the collector of the second transistor is connected to zero single-phase network, the emitter of the first transistor is connected to the emitter of the second transistor, and their common output is intended for connection to the common output of the first and second stator windings, in the second reversing semiconductor switch, the collector of the third transistor is designed to connect to the phase mains supply, the fourth transistor collector is connected to the zero-phase network, the emitter of the third transistor is connected to the emitter of the fourth transistor, and a common output for connection to the common terminal of the second and third stator windings, and the transistors of each reversing a semiconductor switch connected oppositely.

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