SU862304A1 - Device for protecting electric motor against overload and phase breaking - Google Patents

Description

switching element connected to the phase of the network, and the other to the neutral wire, and the closing contact of this relay is included in the circuit of the winding of the switching element.

The drawing shows the scheme of the device.

The device contains a current node 1, included in the motor circuit 2, an executive relay 3 connected through a resistor 4, a diode 5 and the Start button b to the third phase of the network and the neutral wire, magnetic starter 1, contacts 8 of which are connected in parallel to the Start button, button 9 Stop and contacts 10 of the executive relay included in the circuit of the magnetic starter winding, threshold element 11, diodes 12,13,14,15,16,17, capacitors 18,19,20,21, resistors 22,23, potentiometers 24,25 and a thermistor 26, mounted on the motor windings.

The device works as follows.

In the initial state, relays 3, starter 7, and motor 2 are off. The voltage at the output of the current node 1 is zero, the threshold element 11 is closed, the capacitors 18,19,20,21 discharged. As the threshold element 11 can be used dinistor., Unijunction transistor or its equivalent. Potentiometers 2, 25 set the time when the threshold element 11 is turned on.

When the power supply is in full-phase mode and the button B is started, the relay is turned on, contacts 10 of which close the winding circuit of the magnetic actuator 7, the latter is turned on and contacts 8 bypasses the Start button 6. The motor 2 is turned on, with the help of capacitors 18, 19 and 20, the device is tuned from the transient and inrush currents of the motor 2 and from the asymmetry of the voltages between the neutral wire. and the zero point of the motor windings at start. At the end of the transition and start-up modes, the engine 2 operates in nominal mode. The voltage on the capacitors 18,19,20 is not enough to turn on the threshold element 11.

If one of the phases of the mains supply fails and the motor 2 overturns, the wiring at the output of the potentiometer 24 increases and after charging the capacitor 18 through the diode 13 enters the input of the threshold element 11, the latter turns on and bridges the winding of the relay 3. Relay 3 turns off and contacts 10 disconnects The power circuit of the winding of the magnetic starter 7, Magnetic starter 7 disconnects the motor 2 from the mains. The contacts 8 of the magnetic starter 7 open the power circuit of the executive relay 3

The device returns to its original position.

When motor 2 is overloaded, for example, up to 1.5 nominal., The value of the voltage on the condensate e 20 is not enough to open the threshold element 11. At the same time, the temperature of the windings of the engine 2 increases and when it exceeds the maximum allowable value, the resistance of the thermistor 26 increases. The voltage on the capacitor 19 exceeds the value of the turn-on voltage of the threshold element 11, which turns on and shunts the relay 3. The motor 2 is de-energized.

5 In the event of an overload of more than 1.5 of the nominal value, the capacitor 20 is recharged through the resistor 22 to turn on the turn-on voltage of the threshold element 11, and further processes in the circuit are similar to those described.

Thanks to the introduction of the R-C-R chains, in the shoulder of one of which the thermistor is turned on, the reliability of the engine and its protection is increased by

5 to more fully match the protective characteristic of the device with the thermal overload characteristic of the engine. .

Claims (1)

Invention Formula Device to protect the motor against overload and phase failure, containing a current node connected to the motor circuit, one clamp of which is connected to the neutral wire of the network, switching element, Start and Stop buttons, executive relay, threshold element and voltage divider whose input is connected to zero wire and neutral protected motor, and the output is shunted 0 by a capacitor, distinguished by the fact that, in order to increase reliability by creating different shutter speeds at different degrees of motor overload, two RC-I chains are added, one of which includes a thermistor, and the PCR input of the chains is connected to the second terminal current node, and their common output is shuntirol van mentioned by 1F1 threshold element, connected in parallel to a capacitor and an executive winding, which at one end through a resistor, a diode and a Start button, is shunted by a closing contact to mmutiruyuschego  element connected to the phase of the network, and the other to the neutral wire, and the closing contact of this relay is included in the winding circuit of the switching element, 0 Sources of information taken into account during examination 1, USSR Author's Certificate .№ 657510, cl. And 02 H 7/08, 1979,., 2, USSR Author's Certificate 5 No. 670995, class, H 02 H 7/08, 1978.. f 0 0 ef im J / Jt. i. f T tWnPzIi uuUFF / -L