Motor autotransformer step-down starting control circuit
By setting up intermediate relays and time relays in the autotransformer step-down start control circuit, the damage caused by poor contact during starting of the motor and frequent start-up is solved, and the safe operation and delayed start-up function of the motor are realized.
Patent Information
- Application Number
- CN202421636119.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-10
- Publication Date
- 2025-06-03
- Estimated Expiration
- 2034-07-10
AI Technical Summary
The existing autotransformer step-down start control circuit is prone to poor contact problems after long-term use, which may cause the motor to burn, and frequent equipment start-up and the motor will also be damaged if the cooling is not in place.
By providing a first intermediate relay and a second intermediate relay in the circuit, the step-down circuit and the full voltage circuit are safely isolated to avoid the adhesion problem caused by the simultaneous start of the contactor; at the same time, a second time relay is added to ensure that the motor can only be put into use after a sufficient cooling time has passed.
It effectively solves the problem of motor damage caused by poor contact, and delays the motor starting to avoid motor burning due to frequent start-up and insufficient cooling.
Smart Images
Figure CN222940719U_ABST
Abstract
Description
Technical Field:
[0001] The utility model relates to the technical field of motor control, and particularly to an autotransformer step-down starting control circuit. Background Art:
[0002] Autotransformer step-down starting means that when a motor starts, an autotransformer is used to reduce the starting voltage applied to the stator winding of the motor. After the motor starts, the motor is then disconnected from the autotransformer, so as to operate normally under full voltage. The existing autotransformer step-down starting control circuit is as Figure 1 shown. Its control process is as follows: 1. Close the air switch circuit breaker QF to connect the three-phase power supply; 2. Press the start button SB2, the coil of the AC contactor KM1 is energized and self-locked, and its main contacts are closed, connecting the autotransformer coil in star. At the same time, since the auxiliary normally open contact of KM1 is closed, the coil of the contactor KM2 is energized and attracted, and the main contacts of KM2 are closed, and 65% of the three-phase voltage is connected to the motor by the low-voltage tap (for example, 65%) of the autotransformer; 3. The auxiliary normally open contact of KM1 is closed, making the coil of the time relay KT energized and start timing according to the set time. When the time arrives, the normally closed contact of KT's power-on delay is closed, making the coil of the intermediate relay KA energized and self-locked; the power-on delay open contact of KT disconnects the coil circuit of KM2; 4. Since the coil of KA is energized, its normally closed contact disconnects, making the coil of KM1 de-energized, and all the normally open contacts of KM1 are released, and the main contacts are disconnected, opening the star connection end of the autotransformer coil; at the same time, the coil of KM2 is de-energized, and its main contacts are disconnected, cutting off the power supply of the autotransformer; the normally open contact of KA is closed, and through the normally closed contact of KM1 that has been reset and the normally closed contact of KM2 that has been reset, the coil of KM3 is energized and attracted, and the main contacts of KM3 connect the motor to operate under full voltage; 5. The normally open contact of KM1 is also disconnected, making the coil of the time relay KT de-energized, and its delay closed contact is released, which also ensures that after the motor starting task is completed, the time relay KT can be in a de-energized state; 6. When wanting to stop, pressing SB1 will cut off all the power in the control circuit, and the motor is cut off from the power supply and stops rotating.
[0003] However, when the contactors of general large equipment are used for a long time, the main contacts and auxiliary contacts will show carbonization and heat generation phenomena, and finally there will be a phenomenon of poor contact (either unable to contact or stuck together and unable to release); especially during the switching process, it is easy to occur the situation of unable to disconnect or close, resulting in the phenomenon of single-phase operation, which is likely to cause the motor to burn out. Moreover, the equipment will start frequently during operation, especially when starting under the condition that the motor is not cooled sufficiently, which is also one of the reasons for the motor to burn out. Content of the Utility Model:
[0004] The purpose of the utility model is to provide an autotransformer step-down starting control circuit.
[0005] The utility model is implemented by the following technical solutions: A motor autotransformer step-down starting control circuit, which includes a first contactor, a second contactor, a first time relay, a second time relay, a first intermediate relay, a second intermediate relay, a stop button, a start button, and an autotransformer.
[0006] The normally-closed delay-on contact of the second time relay is connected in parallel with the normally-open contact of the second intermediate relay and then connected in series with the coil of the second intermediate relay to form a first branch. The normally-closed contact of the second intermediate relay is connected in series with the coil of the second time relay to form a second branch. The first normally-closed contact of the first contactor, the normally-closed contact of the second contactor are connected in parallel with the circuit formed by the first branch and the second branch and then connected in series with the power supply.
[0007] The first normally-closed contact of the first intermediate relay and the coil of the first contactor are connected in series to form a third branch. The first normally-open contact of the first contactor is connected in parallel with the start button to form a fourth branch. The fourth branch is connected in series with the parallel branch formed by the third branch and the coil of the first time relay to form a fifth branch. The normally-closed delay-on contact of the first time relay is connected in parallel with the first normally-open contact of the first intermediate relay and then connected in series with the coil of the first intermediate relay to form a sixth branch. The second normally-open contact of the first intermediate relay, the second normally-closed contact of the first contactor, and the coil of the second contactor are connected in series to form a seventh branch. The fifth branch, the sixth branch, and the seventh branch are connected in parallel and then connected in series with the stop button, the normally-closed contact of the thermal relay, and the normally-closed contact of the second time relay and then connected to the power supply.
[0008] The circuit breaker, the first main contact of the second contactor, and the thermal relay are connected in series between the power supply and the motor. One end of the autotransformer is connected in series with the first main contact of the first contactor and then connected to the circuit between the circuit breaker and the first main contact of the second contactor. The other end of the autotransformer is connected to the second main contact of the first contactor. The tap of the autotransformer is connected to the circuit between the thermal relay and the motor.
[0009] Further, the third normally-closed contact of the first contactor is connected in series with the stop indicator light to form a seventh branch. The second normally-open contact of the first contactor is connected in series with the step-down operation indicator light to form an eighth branch. The second normally-closed contact of the first intermediate relay is connected in series with the parallel circuit of the seventh branch and the eighth branch and then connected to the power supply.
[0010] Further, the normally-open contact of the second contactor is connected in series with the full-voltage operation indicator light and then connected to the power supply.
[0011] Advantages of the present utility model: A first intermediate relay is provided in the circuit to safely isolate the step-down circuit and the full-voltage circuit, solving the problem of adhesion caused by the simultaneous startup of the first contactor and the second contactor; at the same time, by adding a second intermediate relay and a second time relay, it can be ensured that the motor can be put into use only after sufficient cooling time, thus preventing the problem of motor burnout caused by insufficient cooling and frequent startup. Description of the drawings:
[0012] Figure 1 is an existing autotransformer step-down starting control circuit.
[0013] Figure 2 is the control circuit of the present utility model.
[0014] The first contactor KM1, the second contactor KM2, the first time relay KT1, the second time relay KT2, the first intermediate relay KA1, the second intermediate relay KA2, the stop button SB1, the start button SB2, the autotransformer QSA, the circuit breaker QF, the thermal relay FR, the stop indicator light HL1, the step-down operation indicator light HL2, the full-voltage operation indicator light HL3, and the motor M. Specific implementation manner:
[0015] In the description of the present utility model, it should be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present utility model. In addition, when terms such as "first", "second", "third" appear, they are only for descriptive purposes and cannot be understood as indicating or implying relative importance.
[0016] As Figure 2 shown, a motor autotransformer step-down starting control circuit includes a first contactor KM1, a second contactor KM2, a first time relay KT1, a second time relay KT2, a first intermediate relay KA1, a second intermediate relay KA2, a stop button SB1, a start button SB2, and an autotransformer QSA,
[0017] The power-on delay closing contact of the second time relay KT2 is in parallel with the normally open contact of the second intermediate relay KA2 and then in series with the coil of the second intermediate relay KA2 to form the first branch. The normally closed contact of the second intermediate relay KA2 is in series with the coil of the second time relay KT2 to form the second branch. The first normally closed contact of the first contactor KM1, the normally closed contact of the second contactor KM2 are in parallel with the circuit formed by the first branch and the second branch and then in series with the power supply;
[0018] The first normally closed contact of the first intermediate relay KA1 and the coil of the first contactor KM1 are in series to form the third branch. The first normally open contact of the first contactor KM1 is in parallel with the start button SB2 to form the fourth branch. The fourth branch is in series with the parallel branch formed by the third branch and the coil of the first time relay KT1 to form the fifth branch; The power-on delay closing contact of the first time relay KT1 is in parallel with the first normally open contact of the first intermediate relay KA1 and then in series with the coil of the first intermediate relay KA1 to form the sixth branch. The second normally open contact of the first intermediate relay KA1, the second normally closed contact of the first contactor KM1, and the coil of the second contactor KM2 are in series to form the seventh branch. The fifth branch, the sixth branch, and the seventh branch are in parallel and then in series with the stop button SB1, the normally closed contact of the thermal relay FR, and the normally closed contact of the second time relay KT2 and then connected to the power supply;
[0019] The circuit breaker QF, the first main contact of the second contactor KM2, and the thermal relay FR are connected in series between the power supply and the motor M. One end of the autotransformer QSA is in series with the first main contact of the first contactor KM1 and then connected to the circuit between the circuit breaker QF and the first main contact of the second contactor KM2. The other end of the autotransformer QSA is connected to the second main contact of the first contactor KM1. The tap of the autotransformer QSA is connected to the circuit between the thermal relay FR and the motor M.
[0020] The third normally closed contact of the first contactor KM1 and the stop indicator light HL1 are in series to form the seventh branch. The second normally open contact of the first contactor KM1 and the step-down operation indicator light HL2 are in series to form the eighth branch. The second normally closed contact of the first intermediate relay KA1 is in series with the parallel circuit of the seventh branch and the eighth branch and then connected to the power supply.
[0021] The normally open contact of the second contactor KM2 and the full-voltage operation indicator light HL3 are in series and then connected to the power supply.
[0022] Control process:
[0023] 1. Close the circuit breaker QF, and the stop indicator light HL1 is on;
[0024] 2. Press the start button SB2, and the coil of the first contactor KM1 is energized and self-locked. The two sets of main contacts of the first contactor KM1 are closed, and the star connection of the autotransformer QSA is completed. The motor M starts to operate under reduced voltage, and the reduced voltage operation indicator light HL2 is on while the coil of the first contactor KM1 is energized. At the same time, the coil of the first time relay KT1 is energized and starts timing.
[0025] 3. When the set time of the first time relay KT1 is reached, the normally closed timed closed contact of the first time relay KT1 is closed. The coil of the first intermediate relay KA1 is energized, and the normally open contact of the first intermediate relay KA1 is closed to form self-locking. The normally closed point of the first intermediate relay KA1 is in the open state. The coils of the first contactor KM1 and the first time relay KT1 are simultaneously disconnected and de-energized. At the same time, the normally open point of the first intermediate relay KA1 is closed, the coil of the second contactor KM2 is energized, the main contacts of the second contactor KM2 are closed, and the motor M operates at full voltage, switching from reduced voltage operation to full voltage operation, and the full voltage operation indicator light HL3 is on.
[0026] 4. Press the stop button SB1, and the motor stops running, and the stop indicator light HL1 is on.
[0027] 5. When the motor stops running, the second time relay KT2 starts timing (the initial start time of the second time relay KT2 is set to 0, and it can be set according to the cooling required time after the initial operation stops). The normally closed point of the second time relay KT2 is disconnected, disconnecting the entire start circuit, and at this time the motor cannot start.
[0028] 6. When the set cooling time of the second time relay KT2 is reached, the normally closed timed closed contact of the second time relay KT2 is closed. The coil of the second intermediate relay KA2 is energized, and the second intermediate relay KA2 is energized and self-locked. The normally closed contact of the second intermediate relay KA2 is disconnected, the normally closed point of the second time relay KT2 is disconnected, and the coil of the second time relay KT2 is de-energized. At the same time, the normally closed point of the second time relay KT2 returns to the closed state. At this time, the control circuit of the motor M is ready for starting.
[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A motor autotransformer step-down starting control circuit, characterized in that: It includes a first contactor (KM1), a second contactor (KM2), a first time relay (KT1), a second time relay (KT2), a first intermediate relay (KA1), a second intermediate relay (KA2), a stop button (SB1), a start button (SB2), and an autotransformer (QSA). The power-on delayed closing contact of the second time relay (KT2) is connected in parallel with the normally open contact of the second intermediate relay (KA2) and then connected in series with the coil of the second intermediate relay (KA2) to form a first branch, the normally closed contact of the second intermediate relay (KA2) and the coil of the second time relay (KT2) are connected in series to form a second branch, and the first normally closed contact of the first contactor (KM1), the normally closed contact of the second contactor (KM2) and the circuit formed by connecting the first branch and the second branch in parallel are connected in series and then connected to the power supply; The first normally closed contact of the first intermediate relay (KA1) and the coil of the first contactor (KM1) are connected in series to form a third branch, the first normally open contact of the first contactor (KM1) is connected in parallel with the start button (SB2) to form a fourth branch, and the fourth branch is connected in series with the parallel branch formed by the third branch and the coil of the first time relay (KT1) to form a fifth branch; the power-on delayed closing contact of the first time relay (KT1) is connected in parallel with the first normally open contact of the first intermediate relay (KA1) and then connected in series with the coil of the first intermediate relay (KA1) to form a sixth branch, the second normally open contact of the first intermediate relay (KA1), the second normally closed contact of the first contactor (KM1), and the coil of the second contactor (KM2) are connected in series to form a seventh branch, and the fifth branch, the sixth branch and the seventh branch are connected in parallel with the stop button (SB1), the normally closed contact of the thermal relay (FR), and the normally closed contact of the second time relay (KT2) and then connected to the power supply; The circuit breaker (QF), the first main contact of the second contactor (KM2), and the thermal relay (FR) are connected in series and connected between the power supply and the motor (M); one end of the autotransformer (QSA) is connected in series with the first main contact of the first contactor (KM1) and connected to the circuit between the circuit breaker (QF) and the first main contact of the second contactor (KM2); the other end of the autotransformer (QSA) is connected to the second main contact of the first contactor (KM1); and the tap of the autotransformer (QSA) is connected to the circuit between the thermal relay (FR) and the motor (M).
2. A motor autotransformer step-down starting control circuit according to claim 1, characterized in that: The third normally closed contact of the first contactor (KM1) is connected in series with the stop indicator light (HL1) to form a seventh branch, the second normally open contact of the first contactor (KM1) is connected in series with the step-down operation indicator light (HL2) to form an eighth branch, and the second normally closed contact of the first intermediate relay (KA1) is connected in series with the parallel circuit of the seventh branch and the eighth branch and then connected to the power supply.
3. A motor autotransformer step-down starting control circuit according to claim 1 or 2, characterized in that: The normally open contact of the second contactor (KM2) is connected in series with the full-voltage operation indicator light (HL3) and then connected to the power supply.