A device for slowing down the action of electromagnetic alternating current devices when they are turned off. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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The proposed device relates to electrical engineering and is designed to slow down the action of electromagnetic AC devices when they are turned off.

Mechanical devices are known to slow down the action of electromagnetic devices when they are turned off, containing hydraulic or air dampers, clockwork, rubbing parts, but these devices are complex and short-lived.

Known circuit containing a capacitor connected in parallel to the control coil of the electromagnetic apparatus [1]. However, this circuit requires a constant operating voltage.

The closest to the proposed technical essence and the achieved result is a device containing a control key with two contacts in a switched circuit, a diode is connected in series to each of the contacts, and the diodes are connected in opposite directions, and each of the contacts is shunted by an RC chain.

When the contacts of the control key are closed, the winding of the electromagnetic apparatus is flowed with alternating current, with each half-wave of alternating current passing through the corresponding diode and switch contacts. When the contacts of the control key are opened, the winding of the electromagnetic apparatus continues to flow around with alternating current, while each half-wave of alternating current passes through the corresponding diode and RC circuit. As the capacitors of the RC circuits charge, the amount of current through the winding of the electromagnetic apparatus decreases. When the current drops to a certain value, the electromagnetic device turns off. Thus, between the moment of opening the control key and the moment of switching off the electromagnetic device, there is a certain time delay, determined by the parameters of RC chains [2].

However, the device is not highly reliable due to the fact that when the contacts of the control key are closed, the diodes are constantly flowed around by the load current, and when they are open, they are blocked by a reverse voltage equal to the amplitude value of the mains voltage, i.e. the structure of the circuit is such that it requires continuous operation of the diodes, regardless of the position of the control key, which reduces the time between failures, and hence the reliability of operation.

The presence of charged capacitors in the off position of the key also reduces the time between failures, i.e. reduces reliability.

The device also does not differ in efficiency due to power loss in permanently on diodes and resistors during switching on, especially at a high frequency of operation; requires the installation of two timing chains, a two-pole control key, diodes with a high reverse voltage - all this increases the cost and dimensions of the device, complicates the adjustment.

The figure shows a diagram of a device for slowing down the action of electromagnetic AC devices when they are turned off, free from these shortcomings. The technical solution is protected by copyright [3].

The device contains a control winding KM of an electromagnetic device, which is connected directly to terminal 1 of an alternating current source with one output, and to terminal 2 through a diode bridge rectifier 3 via an alternating current circuit, and a closing contact KM1 of an electromagnetic device.

An RC circuit 3 is included in the diagonal of the bridge rectifier 4 for direct current, in series with the resistor of which the NC contact KM2 of the electromagnetic apparatus is connected. The entire deceleration unit, consisting of a series-connected rectifier 3 and contact KM1, is shunted by the SA control key. The RC circuit resistor has a relatively low resistance - on the order of several tens to hundreds of ohms.

If it is necessary to limit the charge voltage of the capacitor of the RC circuit, the capacitor is shunted with an additional resistor of a relatively large value - on the order of several hundred kilo-ohms (not shown).

The device works as follows. When the SA control key is turned on, the electromagnetic device control winding receives power directly from the terminals 1 and 2 of the AC source, as a result, the KM2 contact opens and the KM1 contact closes.

When the SA key is opened, alternating current continues to flow through the control winding of the KM through the closed contacts of KM 1, diodes of the bridge circuit 3, and the capacitor of the RC circuit 4.

The capacitor is charged, and the amount of current flowing through it decreases, respectively, the current through the control winding of the KM also decreases.

When the current through the KM control winding decreases to a certain value, the electromagnetic device is turned off, as a result, the KM1 contact opens, and the KM2 contact closes, and the capacitor is discharged into the RC circuit resistor 4, preparing the circuit for a second cycle. The necessary deceleration of the shutdown of the KM electromagnetic apparatus is determined by the value of the capacitance of the capacitor of the RC circuit 4.

Since deceleration unit 3 is by alternating current shunted by the NO contacts of the control key SA through the NO contacts KM1 of the electromagnetic apparatus KM, when the contacts of the control key SA are closed, all elements of this unit are not flowed by the load current, which eliminates power losses, increases the time between failures of the device elements, and consequently, the reliability of the device is improved.

When the contacts of the SA key are open, node 3, having worked out the required deceleration time, is disconnected from the network by contact KM1, and the capacitor is discharged by contact KM2, and all elements of the circuit are de-energized again, and the capacitor of the RC circuit 4 is discharged. Thus, the deceleration unit 3 of the proposed device, in comparison with the known one, operates only during the deceleration time of the electromagnetic device, which increases the reliability of the device.

The device is more economical due to the absence of losses in the deceleration node 3 when the device is turned on and operating, it has a lower cost, dimensions and is easier to set up due to the use of one RC circuit, a single-pole control switch, diodes with a lower (twice) reverse voltage provided by the bridge circuit.

Thus, the introduction of an electromagnetic apparatus into the device of closing and breaking contacts, the implementation of a full-wave rectifier, a change in the relationship between the circuit elements makes it possible to increase the reliability and efficiency of the device, reduce its cost and dimensions, and simplify setup.

Details. In the author's version, an intermediate alternating current relay of the RP-25/220 type for a voltage of 220 V / 50 Hz was used as an electromagnetic device, the coil of which had 6700 turns of PEV-2 / 0,14 wire. Switch SA any, suitable for current and voltage. Bridge rectifier diodes 3-diode blocks KTs402A, B-KTs405A, B for 500, 600 V and current up to 1 A or four diodes of the KD105V, G type for 600, 800 V, respectively (green, red dots on the case, respectively). Capacitor timing RC-circuit 4 any electrolytic capacitance of 20...30 microfarads and a voltage of 400, 450 V, MJ1T-2 type resistor with a resistance of 100...200 Ohm. To limit the charge voltage of the capacitor (if necessary), you can use a resistor of the MJ1T-2 type with a resistance of 50 ... 100 kOhm.

Setting. The duration of the deceleration to turn off the electromagnetic apparatus is determined by the charge time of the capacitor of the RC circuit and the release current in this case of the RP-25 relay. Therefore, setting up the device consists in selecting the required capacitance value of the electrolytic capacitor of the RC circuit according to the required deceleration time for releasing the KM electromagnetic apparatus.

References:

1. Komarov A.F. Adjustment and operation of electrical equipment for metal-cutting machines. - M.: Mashinostroenie, 1974. S. 104-111.
2. French patent No. 2173924, class. H01H9/00, 1973.
3. Author's certificate of the USSR No. 1014058, class. H01H47/18.

Authors: K.V. Kolomoitsev, R.M. Kolomoitsev

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