SU1387095A1 - Device for protecting 3-phase electric motor against phase sequence change - Google Patents

Abstract

The invention relates to the field of electrical engineering, in particular to devices for relay protection of an electric motor against phase reversal and seizure. The aim of the invention is to improve the reliability and enhancement of functionality by: implementing protection against seizure of the rotor. Device containing

Description

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Phase sensitive element 7, 8, 9 and rectifier 10 are equipped with a voltage divider 12, 13 at the output, two thyristors 17, 20, two diodes 22, 27 connected to the control electrode of the first thyristor 17, a capacitor 23 connected in parallel a second thyristor 20J resistor 21 connected in series with the second thyristor 20, an executive relay 18 connected in series with the first thyristor 17, two rectifiers The invention relates to electrical engineering, namely, to protection devices for three-phase asynchronous electric motors edovani phases and the rotor jamming.

The purpose of the invention is to increase reliability and enhance functional capabilities by implementing anti-jamming of the rotor.

FIG. 1 shows a diagram of the device; in fig. 2 is a vector diagram illustrating the principle of operation of the block that reacts to a phase rotation disorder.

In the device between the neutral wire and any of the phases of the power supply of the electric motor 1, the Start 2 and Stop 3, buttons are connected in series. and the coil 4 of the actuator of the block-contact 5 of which is connected parallel to the Start button 2. The power contacts 6 of the coil 4 are included in the supply phases of the electric motor 1. The first 7 and second 8 resistors and the capacitor 9 connected in a star are connected to the stators of the stator winding of the electric motor 1. The first rectifier 10, shunted by the first smoothing capacitor 11, is connected to one of the phases of this star in series with the resistor 7, to whose source a voltage divider connected to the third 12 and fourth 13 resistors is connected,

Between the neutral wire and any of the power phases of the electric motors; n 1, the primary windings of the step-down transformer 14 are connected, to the secondary partitions 24, 15, the first of which is parallel with the rotation sensor 26 between the cathode and the control electrode of the second thyristor 20, and the second is parallel to the chain of the first thyristor 17 and relay 18, and a step-down transformer 14 connected between the supply network and the first dispenser 15. The introduction of the rotation sensor 26, the rectifier 24 and the thyristor 20 allows protection against seizure of the rotor. 2 Il.

A second rectifier 15, shunted by a second smoothing capacitor 16, is connected to the secondary winding of which. At the output of the second rectifier 15 is

There are connected in series the first thyristor 17 and the executive relay 18, the disconnections of the contact 19 of which are connected in series with the coil 4 of the starter. In parallel with this

the chain is connected in series with the second thyristor 20 and the resistor 21, the anode of the second thyristor 20 is connected with the control electrode of the first thyristor 17 through the first diode

22, Padallello, to the second thyristor 20, a time delay capacitor 23 is connected. A third rectifier 24 is connected between the control electrode and the anode of the second thyristor 20. Input

which is connected to a rotor rotation sensor 26, shunted by a third smoothing capacitor 25, the output of which is a voltage when the rotor of the engine rotates. The middle point of the voltage divider 12, 13 is connected with the control electrode of the first thyristor 17 through the second diode 27. The device operates as follows

With direct phase rotation, the neutral of the star, consisting of resistors 7 and 8 and capacitor 9, is shifted towards Ug (Fig. 2, point 01). Provided that RT Rg X ,, and R is the sum of the resistances of the resistor 7 and the internal resistance of the first rectifier 10, we get that Ue (

 1.5 U, a Uc, 0.4 Ujp. If the alternation of alternation is disturbed, the neutral shifts towards willows (Fig. 2, point 02). Then V 0,4 U, a and „1,5U. At the same time, the voltage on the first rectifier 10 increases, consequently, the voltage on resistor 12 increases, and through the second diode 27 a signal is sent to the control electrode of the first thyristor 17, which opens and the executive relay 18 is activated. Its contact 19 is opened, the coil 4 is started de-energized, its contacts 6 are opened and the electric motor 1 is disconnected from the network,

In normal operation of the engine 1, the rotor rotation sensor 26 produces a voltage that is applied to the third rectifier 24. The second thyristor 20 opens and the time delay capacitor 23 is not charged. The first thyristor 17 is closed and the executive relay does not work. When the rotor is jammed at the output of the rotor rotating sensor 26, the voltage is absent. The second thyristor 20 is locked, the capacitor 23 starts charging until the voltage of the first thyristor 17 is opened. Through the first diode 22, the first thyristor 17 is opened and the executive relay 18 is activated, its contact 19 is opened, thereby de-energizing coil A of the starter, contacts 6 of which are open- by disconnecting the motor from the network.

The device allows to protect the electric motor when the rotor is jammed and in case of direct phase interruption, to increase the reliability and degree of universality of the electric motor protection.

The proposed device can be used in installations such as conveyors and so on, for electric drives of which the likelihood of such emergency conditions occurring, to - jamming and disruption of phase alternation is quite large and can lead to significant damage.

Claims (1)

Invention Formula A device for protection of a three-phase electric motor against alternation of phase alternation, containing a phase-sensitive element, made in 0 5 o Q 0 a star, one arm of which consists of a capacitor with a terminal for connecting to the first, a second shoulder from the first resistor with a terminal for connecting to the second, and a third shoulder from the second resistor with a terminal for connecting the third stator winding of the electric motor between zero a star point. And the second resistor is connected to the input of the first rectifier, the output of which is connected to the first smoothing capacitor, the actuator, a magnetic starter with power contacts for connecting in series to the wire yes, powering the motor, control circuit of the magnetic starter, consisting of the Stop and Start buttons sequentially interconnected, shunted by the starter's block contact, the breaker contact of the actuator, the magnetic starter coil, equipped with leads for connecting between the phase and the neutral wire of the supply network, the second A rectifier whose output is shunted by a second smoothing capacitor, characterized in that, in order to increase reliability and enhance functionality Protection against seizure of the rotor, it is additionally equipped with a third rectifier, the first and second thyristors, the first and second diodes, a voltage divider made on the third and fourth resistors, a fifth resistor, a step-down transformer with leads for connection between the electric motor and the neutral wire of the network, the rotor rotation sensor connected to the output terminals of the third rectifier, the output of which is shunted by the third smoothing capacitor and connected between the cathode and the control elec To the second thyristor, the anode of which through the fifth resistor is connected to the first power of the coil of the actuator relay and the positive output of the second rectifier, the negative power of which is connected to the cathodes of the first and second thyristor and the negative power of the second and third rectifiers, the anode of the first thyristor is connected to the second output of the executive relay, the control electrode of the first thyristor through the opposite direction The first diode is connected to the anode of the second thyristor, the anode gap — whose cathode is shunted by a time delay capacitor, and through the second oppositely directed diode - to the UCH F2.2 medium At its point, the voltage divider is implemented1 on the third and fourth resistors connected in series and connected to the output of the first rectifier.