CS231814B1 - Device for switching the switching element of the inverter with variable output frequency - Google Patents

Abstract

Circuit for controlling the switching of a switching element of an inverter with a variable output frequency. The invention falls into the field of heavy-current electrical engineering and solves the switching of switching elements of an inverter, in particular for powering synchronous motors without rotor position sensors. It achieves optimal switching of motors depending on the load and speed by using a circuit for evaluating pulses with a constant lead of a constant-frequency control source connected to the counting input of a counter, the write input of which is controlled by an auxiliary memory which is connected to the output of a non-volatile memory or a controller of the protective switching time of the switching element, and to the control input of the counter.

Description

BACKGROUND OF THE INVENTION The invention relates to a circuit for controlling the switching of a switching element of an inverter with a variable output frequency connected to a screen output connected by a counting input to an output of a controlled constant frequency source.

Most controlled drives with synchronous motors use information from the motor rotor position sensor to control the inverter switching elements. Transmitting signals from the sensor is susceptible to interference, despite problems with the mechanical design of the sensor, which is also one of the most sensitive parts of the drive. In order to increase the reliability of the drive, it is therefore advantageous to omit the pulse tachogenerator position sensor and to use a circuit for generating switching pulses with fixed ignition timing pulses relative to natural commutation, for example according to AO No. 222 480.

However, in order to obtain an optimum advance, which is dependent on the load and the engine speed, the pulses must be delayed by a certain angle relative to the fixed advance. Connections that use a variable frequency source proportional to the motor rotation speed, such as AO No. 212 497, are suitable for this purpose. In the absence of a rotor and pulse tachogenerator position sensor, the required variable frequency is difficult to obtain since induced motor voltages can evaluate a maximum of 12 pulses at 360 ° el.

The above mentioned disadvantages of the circuit for controlling the switching of the switching element of the inverter with variable output frequency eliminates the circuit according to the invention, which consists in that the control input is connected to the output of the constant ignition pulse timing circuit with respect to natural commutation. counters and auxiliary memory, the second input of which is either a fixed memory connected by the switch, or the protection element of the switching element and its output is connected to the write input of the counter.

Example of wiring according to the invention for the one switching element is described with reference to the drawing, on which the count input of the counter 1, the output of which is connected to a control electrode of switching element connected source output two constant frequency, controlled by a known circuit 2 P ^ro evaluation pulses SLA constant ignition timing against natural commutation, evaluated from the terminal voltage Um of the motor, for example by the circuit according to AO No. 222 480. The output of this circuit 2 is connected to the control input of counter 1 and auxiliary memory J, either a fixed memory 2 »or a known switching time controller 2 of the switching element, for example according to AO No. 212 497. The output of the auxiliary memory J is connected to the write input of the counter 1.

Counter 2 is set at the time of constant advance pulse Sla. evaluated by circuit 2 from the terminal voltage Um of the motor. The number of pulses to be read by the counter 2 before generating the output switching pulse SIb is stored in the auxiliary memory 2. This value can be read from the fixed memory 1, where it is permanently entered for different loads and motor speeds. Inverter only for constant current starting, the initial value depends only on the speed. Another possibility of obtaining the pulse number reading lies in the memory of the switching time controller 2. The selection is then made depending on the operating status of the drive via switch &. ^{at the} time of setting the counter 2 3®, a constant frequency source 2, which changes the content of the counter 2 «of the prescribed number of pulses, triggers the counter 2 generates a switching pulse S1b. which ensures switching of the switching element at the optimum time.

In the control of the n switching elements, the circuit is provided with n counters 2, while the other circuits are common to the whole circuit, i.e. the outputs of the respective circuit ^{28 are} connected in parallel to the counter control and write inputs of the counter.

Claims (2)

SUBJECT OF THE INVENTION 1. A wiring for controlling the switching of a switching element of an inverter with a variable output frequency, connected to a counter output connected by a counting input to an output of a controlled constant frequency source, having a pulse generator of constant ignition pulses in that, in addition to the constant frequency source (7), a counter control input (1) and an auxiliary memory (3), the second input of which is a switch, are connected to the output of the constant ignition pulse timing circuit (2) (6) either a fixed memory (4) or a switching time controller (9) is connected and the output of which is connected to the write input of the counter (1). Wiring according to claim 1, characterized in that the counting, control and writing inputs "n" of the counters (1) are connected in parallel to the outputs of the auxiliary memory (3), the fixed memory (4) and the constant frequency source (7).