Thyristor device for smooth start of hv synchronous electric motor by underfrequency relay (versions)

FIELD: electricity.

SUBSTANCE: according to the first version, the thyristor device for smooth start of a HV synchronous electric motor by the underfrequency relay contains a dependent frequency converter consisting of a thyristor rectifier, a thyristor inverter, a smoothing choke, a transistor inverter, a transistor inverter with a control unit and a filter capacitor at the outputs, a voltage stabiliser paralleled to the filter capacitor, commutation apparatus connecting the corresponding input and output clamps of the thyristor and the transistor inverter by means of power contacts. According to the second version, the device contains all the elements as per the first version and, additionally, a unit setting the intensity of connection with the transistor inverter control unit and the voltage controller.

EFFECT: decrease of weight, overall dimensions and cost of the device for smooth start of HV synchronous electric motors at reduced pulsations of the electric motor torque in the low-speed area.

8 cl, 3 dwg

The invention relates to the field of electrical engineering and can be used for soft start ball mills, conveyors, fans with static shaft load and large rotating mass, and other similar production mechanisms.

Known thyristor device for frequency start and speed control of high-voltage synchronous motor (refer to the product catalog of open society "" "Motorized equipment" "Thyristor device frequency unstressed start series EBPVD-WITH", www.abs-vniir.ru containing dependent frequency Converter with a DC link, consisting of a thyristor rectifier, thyristor inverter, a smoothing inductor. The motor runs in the frequency control mode is enabled excitement. To the frequency of 5-7 Hz, while EMF of the motor is small, the frequency Converter is forced commutation of the thyristors of the inverter method of interrupting current, based on the sequential transfer thyristors of the rectifier in the inverter mode and back. In the future EMF of the motor increases and the inverter enters the mode of the natural commutation of the phase current due to the electromotive force phase motor, direct the rotating field of the rotor.

The disadvantages of analogue should be attributed to the presence of failures electromagnetic torque the motor to zero when the switching current of its phases in the low speed area, when the current operating phase is reduced to zero and then rise up again (but in a different pair of phases). Dips electromagnetic torque on the shaft of the motor is called a dynamic impacts in the reduction gear mechanism and motor windings, which can lead to their failure.

The closest to the technical nature of the claimed inventions is a thyristor device to control the start and speed control of high-voltage synchronous motor (see report Baburin M.V. and other "Powerful high-speed electric drive" (1X Symposium "Electrical engineering 2030"report 5.08, 29-31 may 2007), adopted as a prototype (see block diagram in figure 1), containing dependent frequency Converter with DC link 2, consisting of a thyristor rectifier 3, the thyristor inverter 4 and the smoothing inductor 5, in order to reduce the switching angles of the thyristors of the inverter in the circuit of each phase winding of the motor includes an additional transistor switches partial voltage phases 20,21,22 made by the schemes of two-phase transistor inverter-four power transistors and the capacitor.

The effect of shortening the time of decay of the current in the phase synchronous motor 1, out of work, can be achieved by introducing a counter-prot is non-current voltage pre-charged capacitor 27 (with closed transistor 23-26). On the outside of the switching current plot chart, when the voltage phase motor maximum and exceeds the rated voltage value of the power transistors of the switch, the phase current of the motor flows in one direction through the open transistor 24 and a reverse diode of the transistor 26, while the other direction of current through the open diode of the transistor 25 and outdoor transistor 23, i.e. the transistor switch on this site current chart bridged.

The drawbacks of the prototype is its increased weight and dimensions and the cost due to the significant number of high-voltage transistors (12 pcs. in transistor switches partial voltage and the need for the installation of three high-voltage capacitors. In addition, the high-voltage transistors are streamed to the load current of the motor and in the long-term steady state after start-up. So for allotment allocated in this mode, the heat loss requires increased cooling radiators, which are transistors, and their additional airflow, which also increases the overall dimensions of the prototype.

The technical result of the proposed device options is to reduce the weight, dimensions and cost of the device soft start voltage is synchronous motors with reduced ripple torque of the synchronous motor in the low speed area.

This technical result is achieved by the fact that the thyristor device for modulating the frequency of the start of high-voltage synchronous motor according to the first variant, containing dependent frequency Converter with a DC link, consisting of a thyristor rectifier, thyristor inverter, a smoothing inductor entered transistor inverter with control unit transistor inverter and a filter capacitor at the inputs, the voltage regulator is connected in parallel with the filter capacitor, switching devices, power contacts connecting the corresponding input and output terminals of the thyristor and transistor inverters. The voltage regulator includes transistor switch connected to one output through the introduction of a decoupling diode, and the other directly with the relevant conclusions of the transistor inverter, voltage sensor, coupled to the first input of the injected voltage regulator. The device has an intensity control device connected to the control unit transistor of the inverter and voltage regulator. Transistor inverter contains current sensors connected to the inputs of the control unit transistor inverter. Transistor inverter made by three-phase bridge rectification circuit and is designed for partial voltage(10-15%).

This technical result is achieved by the fact that the thyristor device for modulating the frequency of the start of high-voltage synchronous motor according to the second variant, containing dependent frequency Converter with a DC link, consisting of a thyristor rectifier, thyristor inverter, a smoothing inductor entered transistor inverter with control unit transistor inverter and a filter capacitor at the inputs, the voltage regulator is connected in parallel with the filter capacitor, switching devices, power contacts connecting the corresponding input and output terminals of the thyristor and transistor inverters, intensity control device connected to the control unit transistor of the inverter and a voltage regulator. The voltage regulator includes transistor switch connected to one output through the introduction of a decoupling diode, and the other directly with the relevant conclusions of the transistor inverter, voltage regulator, voltage sensor, coupled to the first input of the voltage regulator, a second input connected to the transistor key. Transistor inverter contains current sensors connected to the inputs of the control unit transistor inverter. Transistor inverter made by three-phase bridge circuit WYPALL the deposits and designed for partial voltage (10-15%).

The essence of the proposed technical solutions in the first embodiment is that due to the introduction of device three-phase transistor inverter is designed for partial voltage (10-15%) and three-phase bridge rectification circuit, a filter capacitor, voltage regulator, switching devices to disconnect items entered in the field of high voltages at the terminals of the electric motor and the original connection, reduced weight, smaller dimensions and reduced the cost of the device.

The essence of the device according to the second variant is the same as in the first embodiment, and additionally that the device contains an even and intensity control device, allowing the formation rate of change of frequency at the output transistor of the inverter and the voltage on the filter capacitor during starting of the motor in the low speed area.

For an explanation of the proposed technical solutions warrants in figure 2 and figure 3 shows the structural diagram of the claimed invention according to the first variant and second variant, respectively, where the following notation:

1 - synchronous motor;

2 - dependent frequency Converter with a DC link;

3 - thyristor rectifier;

4 - thyristor inverter;

5 - smoothing drath is spruce;

6 - transistor inverter;

7 - control transistor inverter;

8 - filter capacitor;

9 - voltage regulator;

10, 11 - switching devices;

12 - transistor switch;

13 is a decoupling diode;

14 - voltage regulator;

15 - sensor voltages;

16-18 - current sensors;

19 - intensity control device.

The thyristor device for modulating the frequency of the start of high-voltage synchronous motor according to the first embodiment contains a dependent frequency Converter with DC link 2, consisting of a thyristor rectifier 3, the thyristor inverter 4, a smoothing inductor 5, the transistor inverter 6, the calculated partial voltage (10-15%) and three-phase bridge rectification circuit, the power control transistor inverter 7, the filter capacitor 8, the voltage regulator 9, containing the transistor switch 12, a decoupling diode 13, a voltage sensor 15, the voltage regulator 15. Transistor switch 12, one output is connected via a decoupling diode 13, and the other directly with the relevant conclusions of the transistor of the inverter 6, the voltage detector 15 output terminal connected to the first input of the voltage regulator 14. Transistor inverter 6 to output contains the current sensors 16, 17, 18, are connected to the inputs of the control unit Tran is estomago inverter 7.

The device according to the second variant contains all the elements as in the device according to the first embodiment, and additionally intensity control device 19 connected to the inputs of the control unit transistor of the inverter 7 and the voltage regulator 14.

The operation of the device according to options is as follows.

In the initial state of the circuit of the thyristor rectifier thyristor 3 and the inverter 4 are closed and the current in the phases of the synchronous motor 1 is missing. Its rotor relative to the stator windings is in an ambiguous position. Switching devices 10, 11 are included. In the device containing the intensity control device 16, the signal at the output of the generator 16 intensity equal to zero, the voltage across the filter capacitor 8 is also zero, the transistor switch 12 is closed. The transistors of the inverter 6, corresponding to a given initial angle position of the rotor relative to the stator windings are open. When you receive the command to start the synchronous motor 1 causes the excitation current of the rotor, open the thyristors of the rectifier 3 and the specified phase of the stator of the synchronous motor is supplied a constant current level setpoint current limiting occurs. In the synchronous motor 1 is electromagnetic time-dependent magnitude of the set current and the spatial position of the rotor relative to resultyou is its vector of the stator current (varies according to the sine law). Under its influence, the rotor turns and takes a position in which the torque on the motor shaft is equal to the static moment load (operation positioning, i.e. installation of the rotor in the correct position for a given initial angle). The speed of the rotor of the synchronous motor 1 after the completion of the transition process in this mode is equal to zero.

When a command for acceleration of the motor control unit transistor of the inverter 7 selects the control mode and the switching frequency of the inverter 6 (PWM mode with sinusoidal output current using the signals from the current sensors 16-18 as a current feedback mode or cycloon vertor when the rectangular form of the output current when it is not), and the method of controlling the frequency of the output current of the inverter 6, and outputs the command to open the corresponding transistors of the inverter 6. When control signals at the inputs of the transistors of the inverter 6 and they are switched in sequence and the motor starts to rotate. At the same time begin to operate the voltage regulator 14, setting the device in the first embodiment, the maximum voltage value equivalent to the rectified DC voltage of the inverter 6 when the switching frequency of the starter is and work thyristor inverter 4 (5-7 Hz). If the intensity control device 16 in the device according to the second variant, the voltage on the filter capacitor to the maximum value gradually increases as the acceleration of the synchronous motor 1. In the absence of the voltage regulator 9 because of the inequality of the current of the inductor at the output of the rectifier and the input current of the inverter, the accumulation of charge in the filter capacitor and an unlimited increase in the voltage at its terminals. In the presence of the voltage regulator 9 excess current smoothing inductor flows past a transistor inverter through an open transistor prickly 12 of the voltage regulator 9.

After the dispersal of the synchronous motor 1 to a predetermined rotational speed (approximately 5-7 Hz frequency of the rotor current), when possible natural commutation of the phase current of the synchronous motor 1 due to EMF phases induced rotating field of the rotor, switches the operation mode of the synchronous motor 1 with a transistor of the inverter 6 thyristor inverter 4. When this switching devices 10, 11 are disconnected and further acceleration of the synchronous motor 1 to the rated speed is in normal mode.

In the device according to the second variant using the intensity control device 16 prevents abrupt changes of setting the output frequency of the inverter is ora when a sudden change in job and provides a smooth change in frequency when the transition from one frequency to another.

Compared with the prototype, due to the presence in the claimed device transistor inverter with control unit and a filter capacitor at its inputs, voltage regulator, switching devices to turn off the transistor inverter and voltage stabilizer in the field of high voltage and speed of the synchronous motor, and choose additional equipment at a lower voltage drop weight, dimensions and reduces the cost of the proposed devices. Introduction in the device according to the second variant of the intensity control device allows you to smoothly increase the speed of the motor in accordance with a gradual increase in EMF at the terminals of the motor to gradually increase the voltage on the filter capacitor from zero to the maximum value. This allows to reduce the switching power losses in the power transistors, reduce heat, and hence the dimensions of the cooling radiators.

The claimed invention is to be used in the unstressed devices of smooth start synchronous motors EBPVD, widely used in electric cement mills, crushers and other similar mechanisms with the presence of static moment on the shaft during start-up.

1. The thyristor device for modulating the frequency of the start stand tnago synchronous motor, containing dependent frequency Converter with a DC link, consisting of a thyristor rectifier, thyristor inverter, a smoothing inductor, characterized in that the input transistor inverter with control unit transistor inverter and a filter capacitor at the inputs, the voltage regulator is connected in parallel with the filter capacitor, switching devices, power contacts connecting the corresponding input and output terminals of the thyristor and transistor inverters.

2. The device according to claim 1, characterized in that the voltage regulator contains a transistor switch connected to one output through the introduction of a decoupling diode, and the other directly with the relevant conclusions of the transistor inverter, voltage regulator, voltage sensor, coupled to the first input of the voltage regulator, a second input connected to the transistor key.

3. The device according to claim 1, characterized in that the transistor inverter contains current sensors connected to the inputs of the control unit transistor inverter.

4. The device according to claim 1, characterized in that the transistor inverter is made by three-phase bridge rectification circuit and is designed for partial voltage (10-15%).

5. The thyristor device for modulating the frequency of the start of high-voltage si the synchronous motor, containing dependent frequency Converter with a DC link, consisting of a thyristor rectifier, thyristor inverter, a smoothing inductor, characterized in that the input transistor inverter with control unit transistor inverter and a filter capacitor at the inputs, the voltage regulator is connected in parallel with the filter capacitor, switching devices, power contacts connecting the corresponding input and output terminals of the thyristor and transistor inverters, intensity control device connected to the control unit transistor of the inverter and a voltage regulator.

6. The device according to claim 5, wherein the voltage regulator includes transistor switch connected to one output through the introduction of a decoupling diode, and the other directly with the relevant conclusions of the transistor inverter, voltage regulator, voltage sensor, coupled to the first input of the voltage regulator, a second input connected to the transistor key.

7. The device according to claim 5, characterized in that the transistor inverter contains current sensors connected to the inputs of the control unit transistor inverter.

8. The device according to claim 5, characterized in that the transistor inverter is made by three-phase bridge rectification circuit and is designed for cha is divided voltage (10-15%).