SU752713A1 - Reversible electric drive - Google Patents

Description

The bases of the transistors 13 and 14 are directly connected to the terminals I, 12 of the source of the refueling signal, and parallel to their base-emitter junction diodes 9 and 10 are included in the non-conducting direction.

The base-emitter junction of each of the transistors 5 and 6 is shunted by a collector-empirical junction of additional transistors 19 and 20, the bases of which are connected to the collectors of transistors 5 and 6, respectively, through resistors 21, 22, respectively. For the purpose of thermal stabilization and exclusion of the operation mode of the transistors 19, 20 with a dangling base, resistors 23 and 24 are connected in parallel with their control non-conductors. Emitter-base transitions of transistors 3 and 4 are bridged by diodes 25 and 26.

The device works as follows.

In the presence of supply voltage at terminals 7 and 8 and the absence of terminals 11 and 12 of the control signal, all the transistors are closed and there is practically no current in the circuit.

When released at terminals 11, 12 of the control signal with the polarity shown in FIG. 1 without brackets, the transistors 4, 14 will open, because the control sigal provides for the creation of the base current in their control transitions in the circuit: terminal 12, diodes 9, 25, and subsequent connected emitter-base transitions of transistors 4, 14, terminal 12. Falling voltage The diodes 9, 25 provide a back-up and reliable closing of the transistors 13 and 3. The condition of the full conductivity of the transistor 14 ensures series connection through the limiting resistor 16 of the driving voltage of the power tractors 4 and 5, which are connected to the opposite shoulders a hundred. Consequently, simultaneously with the transistor 4, the transistor 5 opens, which ensures the start-up and the operating mode of the motor of the polarity of the control signal under consideration. At the same time, when opening the transistor 4 through the resistor 22, the opening potential is supplied to the control junction of the additional transistor 20. The mode of the transistor 20 is determined by the ratio of the resistance values of the resistors 22 and 24 forming a potentiometric divider in its base circuit and is close to saturation when acting on the specified divider voltage equal to the voltage of the power source; at the same time, at the collector-emitter junction of the transistor, 20 padeii voltage is a few volts. However, in the case under consideration, due to the closed state of transistor 13, the collector circuit of transistor 20 and the base circuit of transistor 6 directly connected to it are de-energized, as a result of which the open state of transistor 20 in this case excludes the cut-off mode

the base of the transistor 6, and the latter is in the closed state. In this case, the transistor 19 will be locked, since its base and emitter have almost the same and the same strength (the resistance of the resistor 21 is 2-3 times more than the resistance of the resistor 23).

The described state of the system is stable until the polarity changes.

control signal. At the moment of change in the polarity of the control signal (this corresponds to polarity, indicated on the terminals 11, 12 in parentheses), the previously open transistors 4, 14, 5 are closed. Transistors 13, 3 are opened. A dynamic brake circuit of an electric motor is formed: right (according to the scheme) terminal crust winding 1, diode 18, power transition of an open tracer 3, left winding clamp

cor. At the same time, the transistor 20, the base circuit of which is under the influence of the sum of the EMF of the winding of the core and power supply voltage, being in the mode of deep saturation, reliably shuns the control transition of the trapsistor 6, keeping it closed, until the sum of the emf and the supply voltage, which is reduced in the process of braking the core, will not become such that the transistor 20

out of saturation state. An increase in the co-current of the collector-emitter junction of transistor 20 will lead to the discovery of the base current of transistor 6 and its opening. This will reduce the potential acting in the control value of the transistor 20. Thanks to the feedback through the resistor 22, the process develops as an avalanche. Due to the trigger effect, the transistor 6 goes into the fully open state and the transistor 20 goes into the closed state. There is a reverse drive. Changing the polarity of the winding of the core 2 of the motor 3 when the transistor 6 is opened does not change the state of the transistors 19 and 5.

Transistor 5 will remain closed because its base current is zero, and transistor 19 opens and, with its power supply, connects the de-energized base of transistor 5 to the emitter.

FIG. 2 shows the time diagrams of the current change and the speed n of the electric motor in the process of periodic reversal. F / y - the voltage of the control signal is also indicated there; / p, / d -

the current inrush values at start-up and during dynamic engine braking; / p is the value of the inrush current of the motor, which would be in direct switching mode.

Pz diagram (see. Fig. 2, b) shows that in one cycle of the reverse of the drive there are two inrush current. Initially, the motor is braked in a dynamic way, the current surge / d at which does not exceed the starting current

/ yy, and then the reverse occurs, the value

current surge at which depends on the system settings.

The duration of the time interval between the beginnings of the first and second current surges is determined by the resistance value of the resistors 21 to 22. As the earliest grows, the specified interval narrows and the second current surge increases.

Thus, in the proposed device, when the polarity of the control signal (f / y) is changed, the engine first transitions to the dynamic braking mode, and then, when the speed significantly decreases, automatically switches to the switching mode. As a result, the current inrush during the reversal process is significantly less (almost 2 times) in the current inrush that occurs in conventional reversible electronic drives with a direct connection (for fng. 2, b), the current curve of the engine with reverse counterinclusion is shown by dashed lines for comparison.

This property of the proposed electric drive, namely the property of automatically limiting current surges during reversal, allows us to significantly increase the reliability of the drive and the utilization rate of power transistors and also reduce the level of current ripple in the source. The reversal time of the engine will increase slightly, as can be seen from the curve shown in FIG. 2, c.

In order to ensure normal operation of the drive circuit in a wide range of operating temperatures, i.e., for thermal stability of properties and characteristics, it is reasonable to include diodes and a resistor in the basic values of transistors 19, 5 and 6, 20.

Claims (2)

1. Lakhtadyr I. S. Systems of electric direct current at transistors. Kiev, “Technique, 1964, p. 81-83, fig. 32. 2. US Patent L 3480849, cl. 318-257 (H2O), 1969.