SU746806A1 - Device for protecting electric motor from incomplete phase modes - Google Patents

Description

I

The invention relates to relay protection and can be used to protect electric motors from non-phase modes.

. Known schemes for the protection of three-phase electric motors from full-phase modes. The principle of operation is based on the control of the current in the phases, the voltage rfa of the precocrants, the voltage on the neutral of the motor 1.

The disadvantage of these protections is the need to install special relay devices. In addition, it cannot be used when connecting the motor windings in a triangle, is

The closest to the invention is a three-phase electric motor protection circuit against incomplete-phase modes, which contains a magnetic starter, a three-phase rectifier to the feed point of which are connected successively the STS and Start button and a magnetic start coil.

unified block-contact magnetic triggering bodies and a resistor 2.

However, it is noted that the starter can be switched off when the network voltage is lowered within acceptable limits (from +5 to -10% of the nominal voltage).

Claims (2)

The aim of the invention is to make it impossible to eliminate the false disconnection of the actuator with an acceptable decrease in the mains voltage. The goal is achieved by the fact that a device for protection of an electric motor against n & full phase modes, containing a magnetic picker and a three-phase rectifier, to the middle point of which the Stop and Start buttons are connected in series, while the Stop button is connected to a chain of consecutively connected magnetic starters and resistor, additionally equipped with a resistor, series-connected diode and thyristor, connected between start and the magnetic starter coil according to the three-phase A rectifier and a 7 resistor are connected between the diode anode and the thyristor control electrode, with the resistor of the chain connected to the point common to the diode and the thyristor, and an auxiliary diode is connected parallel to the coil of the magnetic starter. In addition, the resistor of the chain can be supplied in the form of a signal lamp. , In the drawing, present cxewa motor protection device against non-phase modes. The device contains a magnetic starter with SILOVB1MI contacts 1 | block contacts 2, coil 3 and control buttons Stop 4 and Start 5, three-phase medium-voltage rectifier gel b, diode 7, thyriotor 8, with resistance 9 in the control circuit, signal lamp 10 and auxiliary diode 11. After pressing the Start button 5, a current flows through the thyristor control circuit .8. The thyristor 8 is opened, the coil 3 is wrapped around the current, and the starter is activated, the power contacts 1 and the block contacts 2 are closed. After the button 5 returns to its original position, the thyristor is held. open with a current through the signal lamp 10. When the voltage in one of the phases disappears in the current through the thyristor 8, a pause appears and it closes in the first pautz. After the current-free pause, the voltage does not open the thyristor 8, since diode 7 prevents the flow of current in its control circuit. The disappearance of the current in the coil 3 pr leads to the disconnection of the actuator. Auxiliary diode 11 is needed to improve the closing conditions of the thyristor 8 and predisposing: the appearance of overvoltage on the coil 3. The signal lamp 1O is selected so that its resistance limits the current in the coil to a level that ensures the actuator to be turned off at a lower level. network voltage, for example, up to 60% of nominal. In addition, the signal lamp indicates that the actuator is turned on. The use of the invention makes it possible to choose a reliable protection device for the 064 electric motor of a half-phase mode. in one KOfHiyce with magnetic actuator. This device, by its principle of operation, does not work when the mains voltage drops within acceptable limits. Thus, the described device allows two requirements to be simultaneously two requirements. It is compact, pro-TbiM, and does not work falsely when the network voltage is lowered within acceptable limits. The invention of the device dp z. Protection of an electric motor from non-phase modes, containing a magnetic starter, a three-phase rectifier, to the feed point of which the Stop and Start buttons are connected in series, while the CTCHI button is connected to a chain of consecutively connected block contacts, a magnetic starter and a resistor , characterized in that, in order to increase reliability by eliminating a false disconnection of an actuator when the network voltage is lowered, it is additionally equipped with a resistor, a follower: A diode and thyristor connected between the start button and the magnetic starter coil are in accordance with a three-phase rectifier, and a resistor is connected between the diode anode and the control electrode of the thyristor, while the common point for the diode and the thyristor is connected to the resistor of the chain, An auxiliary diode is connected parallel to the coil of the magnetic starter. 3. The device according to claim 1, which is based on the fact that the mouth of the chick chain is made in the form of a signal lamp ./ Sources of information taken into account during the examination 1, Andreev V. A., Bondarenko E. V. Relein protection, automation and telemechanics in power supply systems. M., Higher School, 1975, p. 314. 2.Ref. Journal 21 J. Energy Systems and Their Automation, 1977, No. 6, 6 F 283, Pat. NDP, CL. 21 from 71.