SU1665487A1 - Device for thermoresistor starting of asynchronous motors - Google Patents

Abstract

The invention relates to electrical engineering and can be used to limit the inrush currents of high-power generator lamps, rectifying devices with capacitors. The aim of the invention is to reduce energy loss. For this, between the midpoint of the connection of the coil 2 of the starting contactor, its disconnecting contact 4, the ballast resistor 9 and the coil 2 of this contactor, the capacitor 11 is connected, the switching contact 10, the control buttons, and the middle point of the contactor and capacitor are connected to the resistor 9 in series with the resistor 9 11 through the make contact 5 of this contactor is intended to be connected to the second phase of the power supply. 1 il.

Description

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The invention relates to electrical engineering and can be used to limit the inrush currents of high-power generator lamps, rectifying devices with capacitors.

The aim of the invention is to reduce energy loss and increase reliability.

The device for the thermistor start of the asynchronous motor 1 contains a starting contactor with a coil 2, three closing power contacts 3, an opening contact 4 and an additional closing contact 5, three thermistors 6-8, one terminals of which are intended to be connected to the phases of the power source, the other terminals of which are connected to one pins of the corresponding closing power contacts 3, the other pins of which are intended for connection to the phases of the stator winding, the ballast resistor 9. One output opens 4 is connected to one output of the closing contact 10 of the control button, the other output of which is connected to one output of the second thermistor 7, one output of the additional closing contact 5 is connected to one output of the coil 2 of the starting contactor and capacitor 11, the other output of the capacitor 11 is connected to one output the ballast resistor 9, the other output of the coil 2 of the starting contactor is connected to the disconnecting contact 12 of the control button, the other output of which is connected to one output of the first thermistor 6, the terminals bypass contactor lugs 13 intended for connection to two phases of the stator windings make contacts 14

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shunt contactor connected in parallel to thermistors.

The device works as follows.

Let thermistors 6-8 have a temperature equal to the ambient temperature.

Since, in this case, the resistance of thermistor 6 is greater than the value at which the contactor operates, the contactor operates, closes its power contacts 3, after which the motor starts smoothly. At the same time, contact 5 is closed and contact 4 is opened, and the starting contactor with coil 2 is under mains voltage. All other elements of the control circuit are turned off (energy losses are excluded).

As the thermo-resistors heat up with 6-8 start-up currents, their temperature increases and the resistance smoothly (exponentially) decreases, the voltage at the motor terminals gradually increases, and the engine -1 accelerates smoothly. At the end of the start-up process, the voltage at the motor terminals rises so much that the bypass contactor with coil 13 is activated, which short-circuits 15 resistors 6-8 with its contacts, after which they start to cool down, preparing for a new start.

If thermistors 6-8 had time to cool to a predetermined limit when RT is Ntcr, then the restart will be similar to that described.

If they did not have time to cool down / R RTCP /, then the voltage drop on the forbidden enabling thermistor (for example, on thermistor 6) will be insufficient, in the coil 2 of the starting contactor the current I Icp. and the contactor does not work, preventing the engine from starting when the thermoresistors are not cooled,

The advantage of this device is to eliminate energy loss, to increase the reliability of the device in operation.

Claims (1)

Invention Formula A device for a thermistor start of an asynchronous electric motor containing a starting contactor with a coil, three closing power and normally closed contacts, a ballast resistor, three thermistors, some of which are intended for connection to the phases power supply source, the other terminals of which are connected to one terminal of the corresponding closing power contacts, the other terminals of which are intended for connection to the phases of the stator winding, One output of the opening contact of the starting contactor is connected to one output of the first thermistor, the other output of the opening contact of the starting contactor is connected to one output of the ballast resistor, a control button, characterized in that, in order to reduce energy losses and increase reliability, a capacitor bypass contactor is inserted into it with coil and with three make contacts, the control button is made in the form of closing and opening contacts; the starting contactor is equipped with an additional closing contact, one output of which is connected to one terminals of the linear coil a contactor and a capacitor; another capacitor lead is connected to one end of a ballast resistor, the other lead of which is connected to one lead of a make contact of the control button, another lead which is connected to another output of an additional closing contact of the starting contactor and to one output of the second thermistor, another output of the coil of the starting contactor is connected to one output of the opening contact of the starting contactor, the other output of which is connected to one output of the first thermistor, the coil contacts of the shunt contactor are intended to be connected to two fa5 of the stator winding, the closing contacts of the shunt contactor are connected in parallel to the corresponding thermistors.