SU613459A1 - Static converter - Google Patents

Description

one

The invention relates to frequency converters (inverters), for example, for frequency control of asynchronous motors.

A known static frequency converter comprising a rectifier, a self-contained inverter and a group of non-return valves, in which a slave inverter powered by a group of non-return valves is used for energy recovery.

With a wide range of changes in the nature of the load (in particular, the power factor), the output voltage changes its shape.

The purpose of the invention is to improve the shape of the output voltage.

This is achieved by the fact that an additional thyristor is connected in parallel to the terminals of the reverse rectifier, to the cathode of which an auxiliary thyristor is connected, the anode connected to the filter capacitor.

The drawing shows a diagram of the transactor.

It contains an inverter thyristor switching node 1, a self-contained inverter 2, a reverse rectifier 3, an extinguishing thyristor 4, a regulating thyristor 5, a storage capacitor 6, a smoothing choke 7, a recuperation unit 8, a load — an asynchronous motor 9.

The converter contains a switching node 1, which provides general or individual switching of thyristors in an autonomous inverter 2. With this construction of the node

switching occurs as the output voltage is controlled in the inverter by the pulse-width modulation method, i.e. multiple switching of the inverter thyristors within the half-cycle of the output frequency. To remove reactive power from the load, a reverse rectifier 3 is used, which is connected to the output terminals of the autonomous inverter 2. To the DC terminals of the reverse rectifier 3 through the thyristor

5, a storage capacitor 6 is connected, the predetermined voltage value on which is maintained by a power take-off by the recovery unit 8 connected to the storage capacitor through a choke 7.

The operation of the circuit proceeds in the following sequence.

After the next switching of the thyristors in the autonomous inverter, the induction motor 9 is disconnected from the supply source. With

In this case, a voltage remains on the stator of the motor for the duration of the rotor current decay (there is a counter-emf of the induction motor). The back-EMF of the motor (especially when the engine is idling at low load) prevents the inverter from adjusting the output voltage and makes it difficult for the inverter to work together on an asynchronous motor.

In order to force the process down, the rotor current is suggested to use a short circuit of the stator of the asynchronous motor 9 by shorting the direct current circuit of the reverse rectifier by extinguishing the thyristor 4. Turning on the thyristor 4 leads to simultaneous disconnection from the storage capacitor 6 of the reverse rectifier 3 through the thyristor 5 leads to simultaneous disconnection from the storage capacitor 6 of the reverse rectifier 3 through the thyristor 5 the disconnecting thyristor 5 is applied the opposite voltage of the storage capacitor. After the damping of the protomo-emf of the motor, the damping drive four restores its regulating properties, since the current through it goes to zero. In order to recover the reactive power of the load and the active power from the asynchronous two-way drive to the power supply network, the reverse rectifier is connected to the storage capacitor by the thyristor 5, and the suppressing thyristor 4 is not turned on in these modes.

Claims (1)

Invention Formula A static converter containing an autonomous inverter, to the output terminals of which a reverse rectifier is connected, connected by its own output terminals through a smoothing choke-capacitive filter with a power recovery unit into a network, characterized in that, in order to improve the output voltage: to the conclusions of said reverse rectifier, an additional thyristor is counter-connected in parallel with The cathode of which is connected to an auxiliary thyristor connected with the filter capacitor by an anode. h GT1