SU752603A1 - Apparatus for protecting self-contained inverter - Google Patents

Description

one

The invention relates to the field of converter technology and can be used in protection circuits of thyristor frequency converters.

A device for protecting an autonomous voltage inverter is known, in which a resistor connected between a controlled electrode and a cathode is used as a thyristor state sensor. In the conductive state of the thyristor, a signal is taken from the resistor proportional to the voltage at the junction of the control electrode-cathode. The processed sensor signal is fed to the output amplifier of the thyristor of the opposite arm. Removing the signal, that is, turning off the previously conducting thyristor, provides the basis for switching on the thyristor of the opposite arm.

However, this device requires galvanically isolated power sources for each sensor, complex conversion circuits of the sensor signal with mandatory galvanic isolation in the conversion circuit, and it is also susceptible to interference due to the small signal amplitude of the sensor signal.

It is also known a device for protecting an autonomous inverter, comprising a source i-tap, a switch, a power controlled rectifier, a sequence

2

included thyristors, current sensors connected in series with each thyristor PN, thyristor control unit, the first group of elements I, delay element, the source being connected through a switch and the power rectifier connected to the thyristor power electrodes, the second inputs of the first group of e; And they are connected to the corresponding outputs of the thyristor control unit, and the outputs of the first brute element I are connected via a delay element to the control input of the power controlled rectifier 2.

15 This device is the closest to the technical essence of the present invention. However, it has low reliability.

The aim of the invention is the growth of

20 reliability of the device.

To achieve this goal, in the nominal outputs of each of the current sensors sequentially with the corresponding outputs of the input generator are connected to the inputs of additional auxiliary rectifiers, each step of the output of the latter through the element NOT connected to the first input of the element AND entered the second group of elements I, the output of which

30 are connected with the electrode of the opposite thyristor, the first inputs of the first group of elements And are respectively connected to the outputs of auxiliary rectifiers, the second inputs of the second group of elements And are respectively connected to the second inputs of the first group of elements And, and the output of the delay element is connected to the control input controlled switch.

The drawing shows the scheme of the proposed inverter protection device.

The device contains a power source 1, a controlled switch 2, a delay element 3, an inverter control unit 4, logic elements AND 5, 6, 7, 8, a power controlled rectifier 9, logic elements HE 10, 11, auxiliary rectifiers 12, 13, generator 14, thyristors 15, 16, inverter, current sensors 17, 18, inverter output 19.

The protected inverter is made on thyristors 15, 16 connected via power controlled rectifier 9 and controlled switch 2 to power supply 1. Consistently with thyristors 15, 16, the corresponding current sensors 17, 18 are connected, the outputs of which through generator 14 and auxiliary rectifiers 12, 13 are connected with the first inputs of the second group of logical elements 7, 8 through the logical elements NOT 10, 11, and with the first inputs of the first group of logical elements 5, 6 - directly. The second inputs of the first and second groups of logic elements And are connected to the control unit of the inverter 4. The outputs of the second group of logic elements And 7, 8 are connected to control electrodes of the corresponding thyristors 15, 16. The outputs of the first group of logic elements And 5, 6 are connected to the inputs of the delay element 3, the output of which is connected to the control inputs of a controlled switch 2 and a power controlled rectifier 9.

The operation of the device is as follows.

When the load current flows through the thyristor 15 of the protected inverter in accordance with the algorithm of its operation, the thyristor 16 is closed. The load current flowing through the thyristor 15 provides a current sensor 17 using a high frequency generator 14 to generate a single signal at the output of the auxiliary rectifier 12. This signal is inverted by logic element 11 and, acting on logic element 8, prevents the control signal from passing the control unit of the inverter 4 to the control electrode of the thyristor 16. In this case, a single signal at the output of the delay element 3, which is supplied to turn off the controlled switch 2 and disrupt the power control pulses the right rectifier 9 is absent. If at the time determined by the algorithm of the inverter control unit 4, the thyristor 15 is forcibly switched, then the current through the latter drops to zero, which leads to the appearance of a zero signal at the output of the auxiliary rectifier 12, a single signal at the output of the logic element AND and the prohibition of the passage of the control signal from the control unit 4 through the logic element 8 to the control electrode of the thyristor 16 is removed. The processes occurring with respect to the thyristor 16 are similar to those described. If the load current by the thyristor 15 fails to switch, the inhibitory signal from element 8 is not removed and the control signal from the control unit of inverter 4 does not pass to the control electrode of the thyristor 16, the thyristor 16 does not turn on. With

In this case, a single signal is fed to the input of the delay element 3 along the circuit of the logic element 5, where with the required time delay a pulse of a given duration is generated to switch off the controlled

switch 2 and breakdown of control pulses of a power controlled rectifier 9. The amount of time delay can be adjusted.

Thus, the proposed device

prevents the possibility of the occurrence of the through-flip mode of the inverter and provides increased reliability of its operation.

Claims (2)

1. USSR author's certificate number 421088, cl. H 02 H 7/10, 1969. 2. US patent number 3611108, cl. H 02t 1/18, 1971 (prototype).