Method for protecting high voltage adjustable rectifiers during disruption of thyristors (variants)

FIELD: automatic control systems for protecting high voltage adjustable rectifiers for powering gas cleaning filters in various industrial branches and in agriculture.

SUBSTANCE: on disruption of thyristors in ac to method, phase of load current impulse front φ is measured as well as thyristor key impulse front phase α, their difference is calculated and, when φ-α is greater than zero, signal is dispatched for disabling automatic switch in powering circuit of rectifier or value of duration of load current impulse T and duration of impulse of phase-shifting device generating impulses for controlling thyristor key t, are measured, value of their difference is computed and, if T-t is greater than zero, signal is formed for disabling automatic switch in power circuit of rectifier.

EFFECT: increased efficiency.

2 cl, 1 dwg

 

The invention relates to the field of electrical gas cleaning from dust and fog in various industries and agriculture and can be used in automatic control systems of high-voltage Converter units power supply electrostatic precipitators and other controlled rectifiers for protection in the breakdown of the thyristors.

There are ways to protect high-voltage Converter units power supply electrostatic precipitators and other controlled rectifiers in excess of a predetermined current value when the overload or short circuit, the maximum value is exceeded high-voltage inverter in the low-load or no-load operation of the Converter, in excess of the setpoint temperature of the cooling reagent (transformer oil), the magnitude of the impedance Converter.

All of these species protection act or the reduction of the angle control of the thyristor key, or a circuit breaker in the mains transformer. These types of protection are used in converters of the type ATPOM, OPMD, OPMDA, APTD, mass-produced in conjunction with the automatic control systems "PVP", "PVP m", "ARP", "ACCO", "SAPPHIRE", and others, to power the electrostatic precipitators, are protected by copyright certificates of the USSR is no 355606, 12821000 and RF patents №№2147468, 2166999, 2168368.

A significant drawback of these methods of protection of high-voltage regulated converters is that they do not provide a reliable high-speed protection of the transducers in the breakdown of the regulatory thyristors. The reason for this is the following: the amount of current of short-circuiting due to the presence in the primary circuit 380 In the current-limiting reactor does not exceed three times the rated current of the inverter, and the minimum amount of current setpoint cutoff circuit breaker is four to five times the rated current of the machine. Protection against overload - thermal protection operates with a time delay of 15-20 seconds depending on the magnitude of the short circuit current, which can lead to failure of the diodes high-voltage rectifier.

Emergency protection system regulation shall be activated in case of short circuit when the voltage on the precipitator below the setpoint voltage and the short circuit current exceeds the preset current limit of the Converter. In the breakdown of the thyristor peak value of the voltage on the precipitator increases sharply. This leads to a series of breakdowns in the collecting space. The control system reduces the angle control, however, reduce the breakdown voltage is on the electrostatic precipitator does not occur due to damage to the thyristors. This leads to continuous breakdowns and lower average voltage. However, the magnitude of the steady-state value of the secondary voltage may exceed the setpoint voltage emergency protection and disconnection of faulty inverter from the mains will not happen. This can lead to the development of the accident and more serious consequences - failure of the high voltage rectifier and transformer.

The aim of the present invention is to increase reliability of a complex system of regulation, Converter unit, the electrostatic precipitator and, as a consequence, the increase in the number of captured dust.

The technical result is achieved by the fact that a new method of protecting high-voltage converters in the breakdown of the thyristor or triac key in the power circuit of the unit.

According to the invention continuously measure the passing phase of the wavefront of the load current ϕ and the phase of the wavefront control thyristor switch - αset by the automatic control system, and compute the value of the phase difference. During normal operation, ϕ-α less than or equal to zero, when the breakdown of the thyristors ϕ-α greater than zero. In this case, generate a signal to the circuit breaker in the supply circuit of the rectifier.

Another distinctive feature of the proposed method to protect the s is that continuously measure the pulse duration of the load current - T and the pulse duration of the phase-shifting device - t and calculate the value of their difference, and if T-t is less than or equal to zero, this is the normal mode of operation, if T-t is greater than zero - emergency mode.

In this case, generate a signal to the circuit breaker in the supply circuit of the rectifier.

Comparative analysis shows that the differences of the proposed method in comparison with the prototype are significant. This allows to make a conclusion about its compliance with the criterion of "inventive step".

The drawing shows a possible variant of the block diagram of the device for implementing the inventive method.

The block diagram (figure 1) contains the circuit breaker 1, the thyristor key 2, the current limiting inductor 3, a high-voltage rectifier unit 4, the electrostatic precipitator 5, a sensor 6, the voltage of the electrostatic precipitator, the integrator 7, the voltage of the electrostatic precipitator, the phase-shifting device 8, block 9 synchronization unit 10 pulse shaping control thyristor key 2, the current sensor 11 of the electrostatic precipitator, block 12 measurements phase of the wavefront of the load current, block 13 extinguish the arc discharge, the crucial device 14, a driver 15 signal emergency stop circuit breaker 1.

The circuit works as follows.

When the ache on the inverter unit and the switching regulator circuit breaker 1 supply voltage and the operation "start" on the thyristor key 2 receive control pulses from the shaper 10, the phase position of which is given the phase-shifting device 8. The initial angle control - αbeg has a minimum value. Thyristor key 2 opens. The electrostatic precipitator 5, you may receive a voltage whose magnitude is slightly lower voltage start kronirovaniye. The current of the electrostatic precipitator is missing.

Simultaneously, the signal proportional to the voltage of the electrostatic precipitator, the sensor 6 is fed to the inputs of the integrator 7 and the block 13 extinguish the discharge in the electrostatic precipitator. From the output of the integrator 7 and the output unit 9 sync inputs respectively 16 and 17 of the phase-shifting device 8 are control signals. The phase-shifting device 8 generates a signal synchronous with the mains supply, phase and duration of which is proportional to the magnitude of the input signal from the integrator 7, i.e. the voltage at the electrostatic precipitator. By increasing the voltage on the precipitator phase and the duration of the signal at the output of the unit 8 increases, which leads to a further increase in the voltage and increase the current of the electrostatic precipitator. The signal from the sensor 11, the voltage conversion unit 4 is supplied to the unit 12 measurements phase front of the current pulse, the output of which the signal is applied to the input 18 of a casting device 14. To the input 19 of the block 14 with the phase-shifting device 8 is supplied to a signal containing information about the phase position of the pulse control the thyristor key, and the input 20 to the output signal from the block 13 extinguish the spark and arc discharges in breakdowns in the electrostatic precipitator.

During normal operation of the precipitator, the phase of the wavefront of the load current - ϕ lags behind the phase of the wavefront control thyristor switch - αand their difference ϕ-α less than or equal to zero. In the breakdown of the thyristor phase of the wavefront of the load current is ahead of the phase of the wavefront control thyristor key, and ϕ-α is greater than zero, in this case, the output of block 14 of a signal, which is input to the unit 15 that generates a switch-off signal of the circuit breaker 1 in the power circuit of the rectifier. During normal operation of the electrostatic precipitator and the breakdowns in the collecting space, the operation unit 14 is blocked by a signal from block 13 blanking input 20 of the decision making unit 14.

Laboratory and industrial tests of the proposed remedies and obtained positive results.

1. The way to protect high-voltage Converter units power supply electrostatic precipitators and other controlled rectifiers in the breakdown of the thyristors in the power circuit of the rectifier, wherein the continuously measure the phase of the wavefront of the load current ϕ and the phase of the wavefront control thyristor key α, calculates their difference, and when ϕ-α greater than zero, form the signal off the increase of the circuit breaker in the supply circuit of the rectifier.

2. The way to protect high-voltage Converter units power supply electrostatic precipitators and other controlled rectifiers in the breakdown of the thyristors in the power circuit of the rectifier, wherein the continuously measure the magnitude of the pulse current load T and the pulse phase-shifting device t that generates the control pulses thyristor key, compute the value of their difference, and if T-t is greater than zero, generate a signal to the circuit breaker in the supply circuit of the rectifier.



 

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1 cl, 2 dwg

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1 cl, 1 dwg

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2 cl, 2 dwg

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