SU905967A1 - Device for starting ac motor provided with electromagnetic brake - Google Patents

Description

The invention relates to electrical engineering and can be used in electric drives for controlling creene mechanisms in the forestry industry, in which mainly asynchronous electric motors equipped with electromagnetic brakes are used.

Devices for starting an AC motor are known, comprising a magnetic starter whose contactors are included in the phase circuits of the AC motor, a multi-phase power source, a control circuit consisting of series-connected Stop buttons

and start buttons

shunt

a contactor-magnetic starter, a brake electromagnet activation relay, the free output of which is connected to one output of the magnetic actuator relay and a second phase of the power supply, the third phase of which is connected to the free output of the Stop button, and the coil is connected to the indicated phases of the power supply source through the closing contact of the electromagnet activation relay. electromagnet (1.

The disadvantage of this device is low reliability when starting the electric motor, since failure of the electromagnet for some reason leads to the failure of the electric motor due to the occurrence of large overloads. Power supply of an electromagnet with alternating current in the presence of riveting in a magnetic

10 leads to its combustion by increasing the air gap. In addition, during the entire time of the brake release, the windings of the twin valve are flowed by the maximum current, and in

In the case of low mains voltage, the starting process of the electric motor is complicated and the time for the release of the electric motor is increased.

Closest to the invention

20 is a device for starting an AC motor, containing a magnetic starter, the contactors of which are included in the phase circuits of the AC motor,

25 AC source, a control circuit consisting of successively digging Stop buttons, a Start button, shunted by a magnetic start contactor of the tel, an electromagnet activation relay.

the free output of which is connected to one output of the magnetic start-up relay and the second phase of the alternating current source, the third phase of which is connected to the free output of the Stop button, the first DC power supply to which the coil of the electromagnet 2 is connected through the closing contact of the electromagnet activation relay.

However, this device also does not provide control over the state of the electromagnet, therefore it is possible to turn on an unresolved motor and, therefore, its failure. reliability of motor start-up is reduced.

The purpose of the invention is to increase the reliability of the launch.

This goal is achieved by introducing an electromagnet state analyzer into a device for starting an AC electric motor equipped with an electromagnetic brake, performed on a current relay with two closing and two opening contacts, a resistor, a current release release accelerator relay with two closing and opening contacts and a relay for preventing the premature start of an electric motor with two closing and opening contacts, with one output of a current relay shunted by series-connected resistors rum, the first closing contact of the relay to exclude the premature start of the electric motor and the opening contact of the accelerator relay of the current relay, is connected to the coil lead of the electromagnet, the other lead of the current relay through the disconnecting contact of the magnetic starter, the second closure contact of the electromagnet on, connected by the first connected in series the closing contact of the acceleration relay of the current relay release and the first disconnecting contact of the current relay is connected to one output of the accelerated relay From the start-up of the current relay, the other output of which is connected to the negative terminals of the DC power supply and the first output of the pre-launch motor exclusion relay, the other output of which through the second break contact of the electromagnet activation relay, shunted by series-connected second closing contacts to prevent the premature start and a relay for releasing the current relay is connected to the positive terminal of the second DC power supply and the first opening contact ohm electromagnet switch-on relay, the second opening contact of the accelerator relay; the point of connection of the Stop and Start buttons.

Fig. 1 is an electrical circuit diagram of the device for starting the electric motor; figure 2 is a current diagram of an electromagnet.

The device contains a magnetic starter, the relay 1 of which is connected by one output to the second phase of an alternating current power source, the third phase of which is connected to the control circuit terminal consisting of series-connected push-button 2 Stop, start-up button 3, mechanical brake coil 5 relay 4 AC motor connected to the shaft 6, in the phase circuit of which the contactors 7 of the magnetic starter are turned on The coil 5 of the brake electromagnet through the closing contact 8, the relay 4 and the diode 9 are connected to the output the terminals of the first source 10 of the DC power supply. A current relay 11 is successively connected with the electromagnet coil 5, the other output of which is connected via the disconnecting contact 12 of the magnetic actuator, the first closing contact 13 and the first disconnecting contact 14 of the electromagnet activation relay 15 to release the current release relay 10, the other output of relay 15 is connected to one output of the relay 16 eliminating the premature start of the electric motor, the second output of which is via the second disconnecting contact 17 of the activation relay. The electromagnet is connected to the per-open disconnecting contact 13 of the electromagnet activation relay and the positive terminal of the second source 18 of the DC power supply. The opening contact 17 is shunted by series-connected repetitive and closing contacts 19 of the relay for preventing the premature start of the electric motor and contact 20 of the relay for releasing the current relay. The closing contact 20 is shunted in parallel by the first closing contact 21 and the second opening contact 22 of the current relay, the second closing contact 23 of which is connected in series with the closing contact 2.4 of the early start exclusion relay, forming a circuit connected between the Stop button 2 and the output of the magnetic starter relay 1 and the bypass switch the contactor 25 magnetic actuator, the contactor 26 of which bypasses the start button. The current relay 11 is shunted by series-connected disconnecting contacts 27 of relay 15, the closing resistor 28 and the first closing contact 29 of the relay for preventing the premature start of the electric motor. The device works as follows. When the Start button 3 is pressed, the relay 4 turns on the electromagnet, the closing contacts 8 and 13 of which operate, connect the brake electromagnet 5 to the sources 10 and 18 of the direct current, and the opening contacts 14 and 17 break the input circuits of the relay 15 and 16, The current Jj in the electromagnet increases (the section Oa of FIG. 2) exponentially only due to the voltage U of the source 18 of the DC power supply, since the source 10 of the DC power supply is disconnected from the coil 5 of the electromagnet, since the diode 9 is locked. When the current Jj reaches a value close to the current Jj-pr of the electromagnet actuation (point a in figure 2, the current relay li triggers and de-energizes the relay 15 by its disconnecting contact 14, which releases the resistor 28 in parallel with the disconnecting contact 27 (contact 29 the relay excluding the premature start of the electric motor is closed at this moment.) The current in the winding of relay 11 decreases from a value close to the magnitude of the current, the lowering of the relay current (point b in Fig. 2). When the electromagnet core moves, its winding inductance increases so the poet the current continues to decrease, and, when reaching the current release value, the current relay releases, its contacts 21 and 22 are triggered, and the relay 16 also turns on. Flight of the same contacts could not lead to release of the current relay when the current relay 16 was released, because The contacts of the relay 11 for a period and simultaneous open state are bounded by contact 20 of the relay 15 accelerating the release of the relay current after releasing the relay 16 by its closing contact 29 The resistor 28 is disconnected, causing the relay 11 to be ready to operate again with the same electromagnet current ( Single with Figure 2). After the motion of the electromagnet crust is completed, its winding current increases along a more gentle exponential (inductance increases), and when the current reaches point O, relay 11 triggers again and turns on the magnetic starter, which by force contacts 7 triggers the motor, blocks its input circuit the contactor 26 bypasses the start button 3, disconnects the coil of the electromagnet 5 from the source 18, so that the electromagnet winding remains connected only to the source 10 of the direct current power supply. The current in the electromagnet gradually decreases (section cd in Fig. 2) to the value of the holding current O ,,. If the electromagnet does not trigger for some reason, then there is no additional reduction in the current in relay 11, it does not release, therefore, relay 16 also does not release. As a result, the magnetic starter relay 1 does not work, i.e. the start of the electric motor does not occur, and after the end of the action on button 3, the start is turned off and the relay 4 is implemented. As a result, the principle is realized: in the system of errors, the control device refuses to start it. The starting system returns to its initial state by pressing the 2 Stop button, as a result of which the relays 4 and relay 1 de-energize, and the relays 15 and 16 operate and prepare the device for the next operation cycle. Thus, the presence of electromagnet state analyzers in the device excludes the possibility of switching on the engine in an unresolved state, as well as additional heating of the electromagnet with an excessively large holding current and riveting of its magnetic system. The reliability of the launch increases. The device for starting an AC motor equipped with an electromagnetic brake, contains a magnetic starter whose contactors are included in the phase circuits of an AC electric motor, an alternating current source, a control circuit that is connected in series with each other Stop and button Start button bypassing the contactor of the magnetic starter, relay the electromagnet of the electromagnetic brake, the free output of which is connected to one output of the relay magnetic puzzlate and the second phase AC power supply, the third phase of which is connected to the free first water source of the DC power button, parallel to which through the first make contact of the electromagnet activation relay and diode the electromagnet coil is connected, and the second DC power source, t l and h This is due to the fact that, in order to increase the reliability of the start-up, an electromagnet state analyzer is introduced into it.

Claims (1)

Claim A device for starting an alternating current electric motor equipped with an electromagnetic brake, comprising a magnetic starter, the contactors of which are included in the phase circuits of the alternating current electric motor, an alternating current power supply, a control circuit including a stop button and a start button¹', shunted by the contactor of the magnetic starter, the electromagnetic relay of the electromagnetic brake, the free output of which is connected to one terminal of the magnetic starter relay and the second phase of the AC power source, the third phase of which is connected to the free output of the Stop button, the first DC power source parallel to which an electromagnet coil is connected through the first make-up contact of the electromagnet enable relay and the diode, and the second DC power supply, therefore, oh, in order to increase the reliability of start-up, an electromagnet state analyzer is introduced into it, made on a current relay with two NO and NC contacts, a resistor, an acceleration relay for releasing a current relay with two NO and NC contacts and an exception relay for premature start of an electric motor with two NO and opening contacts, moreover, one terminal of a current relay shunted in series with a resistor, the first closing contact of the relay for preventing premature start of the electric motor and p an alternating contact of the relay for accelerating the release of the current relay, connected to the output of the coil of the electromagnet, another terminal of the current relay through the NC contact of the magnetic starter, the second NO contact and the first NC contact of the relay on the electromagnet, shunted in series with the first NO contact of the relay for accelerating the release of the current relay and the first NC contact current relay, connected to one terminal of the relay for accelerating the release of the current relay, the other terminal of which is connected to the negative terminal of the pi voltage of direct current and the first output of the relay for preventing premature start of the electric motor, the other output of which is shunted through the second NC contact of the relay for switching on the electromagnet serially connected by the second closing contacts of the premature start exclusion relay and the relay for accelerating the release of the current relay, connected to the positive terminal of the second⁵ of the DC power supply and the first NC contact of the electromagnet enable relay, the second NC contact of the acceleration relay for releasing the current relay is bridged in parallel with the first NC and second NC contacts of the current relay, the second NC contact of which and the NC contact of the premature start relay 15 of the electric motor form a series circuit connected between the second terminal of the magnetic starter relay and the connection point of the Stop ¹ and Start buttons and shunted 2Q by the contactor of the magnetic starter.