SU758284A1 - Switching device - Google Patents

Description

The invention relates to power engineering and is intended for switching AC power systems.

A switching device is known which contains parallel-connected contacts of an electromechanical switch and a semiconductor switch ⁵ [1]. .

The disadvantage of this device is the relatively high internal resistance of the semiconductor - switch, which leads to losses and lower efficiency of the entire device.

The closest in technical means and the achieved effect to the proposed is a switching device containing a command element, parallel connected contacts of an electromechanical switch and a semiconductor switch, the control electrode of which is connected to the sensor of the monitored parameter through a logic unit (2] ·

.. This device to ensure the extinction of the arc arising from the opening of mechanical contacts, requires an additional source that creates a magnetic field, moving ²

lean arc on the extra electrode. In this case, the greater the magnitude of the switched current and the inductance of the load, the more powerful the field is required to move the arc.

This reduces the efficiency of the entire device. In addition, when the load is turned on by means of a mechanical contact, the shape of the mains voltage curve is distorted, which degrades the operation modes of other consumers connected to the mains. The purpose of the invention is to increase the efficiency of the device without distorting the voltage form of the supply set.

For this, the proposed device is equipped with a diode and serially connected by a single vibrator, a rectifier and a differentiating chain connected between the control electrode of a semiconductor switch sensor, the logic unit contains an element And, to one of the inputs of which a command element is connected, and another input is connected to the sensor and through a diode - with the input of the differentiating chain.

The drawing shows the block diagram of the switching device.

758284

It contains a parallel-connected semiconductor switch 1 and contacts 2 of an electromechanical switch 3 with an electromagnet 4 winding, to which command element 5 is connected, an AND 6 logic element, the output of which is connected via a series-connected differentiating chain 7, rectifier 8 and one oscillator 9 to the controlling semiconductor electrode switch. One of the inputs of the And element is connected to a command element and the other to the sensor 10 of a monitored parameter and through diode 11 to the input of a differentiating chain.

As a command element ^, a key, a button, a relay ₁₅ sensor, etc. can be used.

The device works as follows.

In the initial state, the system is de-energized, a voltage is applied to the switching device, and there is no signal at the input of the command element 20.

If necessary, a constant signal appears at the output of the command element 5, which is fed to the winding 4 of the electromagnet and simultaneously to one of the inputs 25 of the logic element 6. At its second input, a signal comes from the sensor 10, which generates pulses at its output at the time of the voltage transition network through zero value.

At the simultaneous appearance of signals at the equipments ₃ θ of their inputs of logic element 6, the output of the latter receives a signal that enters the input of the differentiating chain 7 and simultaneously through diode I to the pulse input of the logic element 6, remembering the signal ₃₅ from the sensor 10. As a result of differentiation to the input of the one-shot through the rectifier 8 receives a triggering pulse. The one-shot 9 is a displaced trigger having one steady state. When po- stupefying ₄₀ at its input trigger pulse monostable multivibrator 9 is tilted and delivers to the control electrode of the semiconductor switch 1 pulse whose duration is determined by the monostable circuit elements ₄₅ and greater than the response time of the electromechanical switch.

After the signal from the command element 5 arrives at the electromagnet 4, the anchor of the switch 3 comes into motion and closes contact _{5 with 5} θ. Since the turn-on time of switch 1 is significantly less than the turn-on time of switch 3, the load current will flow through switch 1 , consequently, the con- - ₅ cycle 2 will close in the de-energized state. After a time sufficient for reliable closure of contact 2, the one-shot 9 returns to its original (stable) state,

turning off the switch 1. The time constant of the one-shot ensures reliable operation and release of the electromechanical switch '.

In the on position, the device is before the command element 5 removes the control signal. After removing the control signal by the command element, the signal at the output of the logic element 6 abruptly drops to zero. When this differentiating chain 7 through the rectifier 8 delivers to the input of the one-shot 9 trigger pulse. As a result, the semiconductor is turned on. A new switch for a time longer than the switch-off time of switch 3. At the same time, the armature of switch 3, which opens its contacts, begins. After opening the contacts of the switch 3 (ony is de-energized, since switch 1 is on), the one-shot 9 returns to its original state, removing the control signal from switch 1.

When the anode current of the switch 1 passes through zero, it is automatically disconnected.

Thus, the device turns on at zero voltage and turns off at zero current, which allows · to increase efficiency without distorting the voltage form of the supply network and reduce the weight and dimensions of the semiconductor switch due to the fact that it turns on only for a time determined by the single vibrator.

In addition, the device reduces electrical wear from arcing and sparking of contacts, which increases the service life of the device and facilitates its maintenance.

Claims (1)

Claim A switching device containing a command element, parallel-connected contacts of an electromechanical switch and a semiconductor switch, whose control electrode is connected via a logic unit to a sensor of a monitored parameter, characterized in that, in order to increase efficiency without distorting the form of the supply voltage, it is equipped with a diode connected in series one-shot, rectifier and differentiating chip connected between the control electrode of the semiconductor switch and the sensor The logical block contains the element I, to one of the inputs of which the command element is connected, and the other input is connected to the sensor 'and through the diode to the input of the differentiating switch.