Load protection circuit and method for dual power supply switching

Abstract

The invention discloses a load protection circuit and method for dual power supply switching, and the circuit comprises a load circuit and a control circuit, the load circuit comprises a dual power supply switching module which is used for controlling the access states of a main power supply and a standby power supply, and the main power supply and the standby power supply are not accessed at the same time; the motor protector is used for monitoring the state of the load circuit and pre-judging and protecting the fault of the load circuit; the contactor is used for controlling starting or stopping of a load; the control circuit comprises a remote and local change-over switch SA, a remote DCS stop contact SBS, a remote DCS start contact SBR, a local stop switch SB2, a local start switch SB1, a first power-off time-delay relay and a second power-off time-delay relay. When a main power supply and a standby power supply are switched, stable transition of load power supply can be realized by utilizing delay actions of a normally-closed contact and a normally-open contact, and the reliability and continuity of load power supply are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical control, and specifically refers to a load protection circuit and method for dual-power supply switching. Background Art

[0002] In the field of industrial production, with the rapid development of the industrial economy and the continuous improvement of the degree of automation, more and more high-precision industrial products and equipment are being applied, and the requirements for power supply reliability are also getting higher and higher. To meet the requirements of the load for continuous power supply, a dual-power supply scheme is usually adopted, that is, a dual-power conversion device is used to realize the power supply switching between the main power supply and the standby power supply. When the power supply of the main power supply is abnormal, the main power supply and the standby power supply connected by the dual-power switching device are used to disconnect the main power supply and then immediately connect the standby power supply to maintain the subsequent power supply of the load, so that the load will not stop working due to a problem with one power supply.

[0003] At present, during the power conversion process of the dual-power conversion device, the execution logic of the electromechanical operating mechanism or the electronic action mechanism adopted by the dual-power switching device usually follows the principle of "break first and then close", that is, when switching the power supply, the main power supply is first disconnected and then the standby power supply is connected. Due to the influence of mechanical inertia and contact action time, this switching method has a switching time of dozens of milliseconds or even longer. Therefore, the load will experience a short power outage during the switching process. Although the power outage time is very short, for highly sensitive loads with strict requirements for power supply continuity, such as loads controlled by contactors for starting and stopping, this short power outage will still cause the problem that the load stops running after the device is switched, resulting in huge economic losses and safety accidents.

[0004] To solve the problem that the load stops running after dual-power supply switching, those skilled in the art have been seeking methods to effectively prevent the load from stopping running during the dual-power supply switching process, so as to improve the reliability and continuity of the load power supply and eliminate the influence of the load stopping running caused by power supply switching. Summary of the Invention

[0005] The purpose of the present invention is to provide a dual-power supply switching control circuit and method for solving the problem of the load stopping running caused by dual-power supply switching, improving the reliability and continuity of the load power supply, and preventing the load from stopping running.

[0006] In a first aspect, an embodiment of the present invention provides a load protection circuit for dual - power supply switching, which includes a load circuit and a control circuit. The load circuit includes: a dual - power supply switching module, a motor protector, and a contactor. The dual - power supply switching module is used to control the access states of the main power supply and the standby power supply, where the main power supply and the standby power supply are not connected simultaneously. The motor protector is used to monitor the state of the load circuit and predict and protect against faults in the load circuit. The contactor is used to control the start or stop of the load. The special feature is that:

[0007] The control circuit includes: a remote - local switching switch SA, a remote DCS stop contact SBS, a remote DCS start contact SBR, a local stop switch SB2, a local start switch SB1, a first power - off delay relay, and a second power - off delay relay;

[0008] The remote - local switching switch SA is used to switch between remote and local control. When switched to local control, it controls the control circuit of the local stop switch SB2 and the local start switch SB1 to be connected. When switched to remote control, it controls the control circuit of the remote DCS stop contact SBS and the remote DCS start contact SBR to be connected;

[0009] The remote DCS stop contact SBS is used to control the power supply of the first power - off delay relay to be disconnected according to the stop operation of the remote DCS;

[0010] The remote DCS start contact SBR is used to control the power supply of the first power - off delay relay to be connected according to the start operation of the remote DCS;

[0011] The local stop switch SB2 is used to control the power supply of the first power - off delay relay to be disconnected according to the local stop operation;

[0012] The local start switch SB1 is used to control the power supply of the first power - off delay relay to be connected according to the local start operation;

[0013] The first power - off delay relay is used to control the power supply of the contactor to be connected according to any one of the start operations of the remote DCS start contact SBR or the local start switch SB1, so that the load runs. According to any one of the stop operations of the remote DCS stop contact SBS or the local stop switch SB2 or the protection action of the motor protector, it controls the power supply of the contactor to be disconnected, so that the load stops running and maintains a preset duration, avoiding the load immediately resuming operation after the stop operation disappears;

[0014] The second power-off delay relay is used to keep the energized circuit of the contactor connected during the switching process of the dual-power switching module, and restore the energized state of the contactor after the dual-power switching module completes the switching, so as to prevent the load from experiencing instantaneous power failure during the power supply switching.

[0015] As a preferred solution, one end of the dual-power switching module is connected to the main power supply or the standby power supply, the other end of the dual-power switching module is connected to one end of the normally open main contact KM11 of the contactor, the other end of the normally open main contact KM11 of the contactor is connected to one end of the coil MP1 of the motor protector, and the other end of the coil MP1 of the motor protector is connected to the load.

[0016] Furthermore, the power supply live wire L is connected to one end of the remote / local switching switch SA, and the other end of the remote / local switching switch SA is respectively connected to one end of the remote DCS stop contact SBS, the remote DCS start contact SBR, the local stop switch SB2, and the local start switch SB1.

[0017] Even further, the other ends of the remote DCS stop contact SBS and the local stop switch SB2 are connected to one end of the coil KT1 of the first power-off delay relay, and the other end of the coil KT1 of the first power-off delay relay is connected to the neutral wire N of the power supply.

[0018] Still further, the other ends of the remote DCS start contact SBR and the local start switch SB1 are connected to one end of the normally closed contact KT11 of the first power-off delay relay, the other end of the normally closed contact KT11 of the first power-off delay relay is connected to one end of the coil KM1 of the contactor, and the other end of the coil KM1 of the contactor is connected to the neutral wire N of the power supply.

[0019] As a preferred solution, the coil KT2 of the second power-off delay relay is connected in parallel between the other end of the normally closed contact KT11 of the first power-off delay relay and the neutral wire N of the power supply.

[0020] Furthermore, the power supply live wire L is also connected to one end of the contact MP11 of the motor protector, the other end of the contact MP11 of the motor protector is connected to one end of the coil KT1 of the first power-off delay relay, and the other end of the coil KT1 of the first power-off delay relay is connected to the neutral wire N of the power supply.

[0021] Further, the live wire L of the power supply is also connected to one end of the normally open contact KT21 of the second power-off delay relay. The other end of the normally open contact KT21 of the second power-off delay relay is connected to one end of the normally closed contact KT11 of the first power-off delay relay. The other end of the normally closed contact KT11 of the first power-off delay relay is connected to one end of the coil KM1 of the contactor. The other end of the coil KM1 of the contactor is connected to the neutral wire N of the power supply.

[0022] In a second aspect, an embodiment of the present invention provides a dual-power switching control method for preventing load power failure, including the following steps:

[0023] When the circuit is powered by the main power supply and is waiting for a start operation, the normally closed contact KT11 of the first power-off delay relay is closed, the normally open contact KT21 of the second power-off delay relay is open, the coil KM1 of the contactor is de-energized, the normally open main contact KM11 of the contactor is open, and the load is in a stopped operation state;

[0024] According to the state of the local-remote switching switch SA, perform the corresponding start operation; if local control is selected, close the local start switch SB1, the coil KT2 of the second power-off delay relay is energized, the normally open contact KT21 of the second power-off delay relay is closed. After the normally open contact KT21 of the second power-off delay relay is closed, the local start switch SB1 can be disconnected, and the normally open contact KT21 of the second power-off delay relay remains closed. The coil KM1 of the contactor is energized, the normally open main contact KM11 of the contactor is closed, and the load runs; if remote control is selected, close the remote DCS start contact SBR, the coil KT2 of the second power-off delay relay is energized, the normally open contact KT21 of the second power-off delay relay is closed. After the normally open contact KT21 of the second power-off delay relay is closed, the remote DCS start contact SBR can be disconnected, and the normally open contact KT21 of the second power-off delay relay remains closed. The coil KM1 of the contactor is energized, the normally open main contact KM11 of the contactor is closed, and the load runs;

[0025] During the operation of the load, if the coil MP1 of the motor protector detects a fault in the load circuit, the contact MP11 of the motor protector closes, the coil KT1 of the first power-off delay relay is energized, the normally closed contact KT11 of the first power-off delay relay opens, the coil KT2 of the second power-off delay relay loses power, and at the same time, the coil KM1 of the contactor loses power. The normally open main contact KM11 of the contactor opens, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay opens, the contact MP11 of the motor protector can be disconnected. The normally closed contact KT11 of the first power-off delay relay remains open for a preset duration, the coil KT2 of the second power-off delay relay remains de-energized, and starts timing; when the timing time reaches the preset duration, the normally open contact KT21 of the second power-off delay relay opens, the coil KM1 of the contactor remains de-energized, and the normally open main contact KM11 of the contactor remains open, causing the load to remain stopped;

[0026] During the operation of the load, corresponding stop operations are performed according to the status of the remote / local changeover switch SA. If local control is selected, the local stop switch SB2 is closed, the coil KT1 of the first power-off delay relay is energized, the normally closed contact KT11 of the first power-off delay relay is opened, the coil KT2 of the second power-off delay relay is de-energized, and at the same time, the coil KM1 of the contactor is de-energized, and the normally open main contact KM11 of the contactor is opened, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay is opened, the local stop switch SB2 can be disconnected, the normally closed contact KT11 of the first power-off delay relay remains open for a preset duration, the coil KT2 of the second power-off delay relay remains de-energized, and starts timing. When the timing time reaches the preset duration, the normally open contact KT21 of the second power-off delay relay is opened, the coil KM1 of the contactor remains de-energized, and the normally open main contact KM11 of the contactor remains open, causing the load to remain stopped. If remote control is selected, the remote DCS stop contact SBS is closed, the coil KT1 of the first power-off delay relay is energized, the normally closed contact KT11 of the first power-off delay relay is opened, the coil KT2 of the second power-off delay relay is de-energized, and at the same time, the coil KM1 of the contactor is de-energized, and the normally open main contact KM11 of the contactor is opened, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay is opened, the remote DCS stop contact SBS can be disconnected, the normally closed contact KT11 of the first power-off delay relay remains open for a preset duration, the coil KT2 of the second power-off delay relay remains de-energized, and starts timing. When the timing time reaches the preset duration, the normally open contact KT21 of the second power-off delay relay is opened, the coil KM1 of the contactor remains de-energized, and the normally open main contact KM11 of the contactor remains open, causing the load to remain stopped.

[0027] During the operation of the load, when the load power supply is switched, the entire circuit will lose power for a short time. The coil KM1 of the contactor is de-energized, the normally open main contact KM11 of the contactor is opened, and the load enters the stopped state. At the same time, the coil KT2 of the second power-off delay relay is de-energized, and the normally open contact KT21 of the second power-off delay relay remains closed and starts timing. During the timing time, the load power supply switchover is completed. The coil KM1 of the contactor is energized through the normally open contact KT21 of the second power-off delay relay that remains closed, and the normally open main contact KM11 of the contactor is closed, causing the load to resume operation. After the coil KT2 of the second power-off delay relay is energized, it resets and stops timing, and the normally open contact KT21 of the second power-off delay relay remains closed to ensure the continuous operation of the load and prevent the load from stopping when the power supply is switched and loses power for a short time.

[0028] As a preferred solution, the delay preset duration of the normally closed contact KT11 of the first power-off delay relay is greater than that of the normally open contact KT21 of the second power-off delay relay; the delay preset duration of the normally open contact KT21 of the second power-off delay relay is greater than the load power supply switching duration.

[0029] The present invention has the following beneficial effects:

[0030] (1) Through the cooperation of the first power-off delay relay and the second power-off delay relay, when the load power supply is switched, by using the delayed actions of the normally closed contact of the first power-off delay relay and the normally open contact of the second power-off delay relay, a smooth transition of the load power supply is achieved. Further, the delayed disconnection time of the normally closed contact of the first power-off delay relay is greater than the delayed closing time of the normally open contact of the second power-off delay relay, ensuring that there is always a path in the load power supply circuit during power supply switching or power-off instant, thus smoothly avoiding instantaneous power loss of the load.

[0031] (2) Through the local-remote switching switch, the local or remote control mode can be selected according to actual needs. In the local control mode, manual operations can be performed through the local stop switch and the local start switch, which is convenient for on-site maintenance and debugging; in the remote control mode, instructions from the remote system can be received through the remote stop switch and the remote start switch, realizing centralized monitoring and management, and improving the control flexibility and operation convenience of the system. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of a specific embodiment of a load protection circuit for dual power supply switching of the present invention.

[0033] Figure 2 It is a schematic flow diagram of a specific embodiment of a dual power supply switching control method for preventing load power-off of the present invention.

[0034] Description of the reference numerals: Dual power supply switching module 1; Motor protector 2; Contactor 3; First power-off delay relay 4; Second power-off delay relay 5. Detailed Embodiments

[0035] The embodiments of the present invention will be described in more detail with reference to the drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not used to limit the protection scope of the present invention.

[0036] The technical solution of the present invention will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0037] Embodiment 1

[0038] As Figure 1 shown in the structural schematic diagram of the load protection circuit for double power supply switching in an embodiment of the present invention, as Figure 1 shown, it includes a load circuit and a control circuit. The load circuit includes: a dual power supply switching module 1, a motor protector 2, and a contactor 3. The dual power supply switching module 1 is used to control the access states of the main power supply and the standby power supply, where the main power supply and the standby power supply are not connected simultaneously. The motor protector 2 is used to monitor the state of the load circuit and predict and protect against faults in the load circuit. The contactor 3 is used to control the start or stop of the load.

[0039] The control circuit includes: a remote / local switching switch SA, a remote DCS stop contact SBS, a remote DCS start contact SBR, a local stop switch SB2, a local start switch SB1, a first power-off delay relay 4, and a second power-off delay relay 5.

[0040] The remote / local switching switch SA is used to switch between remote and local control. When switched to local control, it controls the control circuit of the local stop switch SB2 and the local start switch SB1 to be connected. When switched to remote control, it controls the control circuit of the remote DCS stop contact SBS and the remote DCS start contact SBR to be connected.

[0041] The remote DCS stop contact SBS is used to control the power supply of the first power-off delay relay 4 to be disconnected according to the stop operation of the remote DCS.

[0042] The remote DCS start contact SBR is used to control the power supply of the first power-off delay relay 4 to be connected according to the start operation of the remote DCS.

[0043] The local stop switch SB2 is used to control the power supply of the first power-off delay relay 4 to be disconnected according to the local stop operation.

[0044] The local start switch SB1 is used to control the power supply of the first power-off delay relay 4 to be connected according to the local start operation.

[0045] The first power-off delay relay 4 is used to control the power supply of the contactor 3 to be turned on according to any one of the start operations of the remote DCS start contact SBR or the local start switch SB1, so that the load operates; according to any one of the stop operations of the remote DCS stop contact SBS, the local stop switch SB2 or the protection action of the motor protector 2, control the power supply of the contactor 3 to be disconnected, so that the load stops operating, and maintain a preset duration to prevent the load from immediately resuming operation after the stop operation disappears.

[0046] The second power-off delay relay 5 is used to keep the energized circuit of the contactor 3 connected during the switching process of the dual power supply switching module 1, and restore the energized state of the contactor 3 after the dual power supply switching module 1 completes the switching, to prevent the load from experiencing momentary power failure during the power supply switching.

[0047] One end of the dual power supply switching module 1 is connected to the main power supply or the standby power supply. The other end of the dual power supply switching module 1 is connected to one end of the normally open main contact KM11 of the contactor 3. The other end of the normally open main contact KM11 of the contactor 3 is connected to one end of the coil MP1 of the motor protector 2. The other end of the coil MP1 of the motor protector 2 is connected to the load.

[0048] The power supply live wire L is connected to one end of the remote / local switching switch SA. The other end of the remote / local switching switch SA is respectively connected to one end of the remote DCS stop contact SBS, the remote DCS start contact SBR, the local stop switch SB2, and the local start switch SB1.

[0049] The other ends of the remote DCS stop contact SBS and the local stop switch SB2 are connected to one end of the coil KT1 of the first power-off delay relay 4. The other end of the coil KT1 of the first power-off delay relay 4 is connected to the neutral wire N of the power supply.

[0050] The other ends of the remote DCS start contact SBR and the local start switch SB1 are connected to one end of the normally closed contact KT11 of the first power-off delay relay 4. The other end of the normally closed contact KT11 of the first power-off delay relay 4 is connected to one end of the coil KM1 of the contactor 3. The other end of the coil KM1 of the contactor 3 is connected to the neutral wire N of the power supply.

[0051] The coil KT2 of the second power-off delay relay 1 is connected in parallel between the other end of the normally closed contact KT11 of the first power-off delay relay 4 and the neutral wire N of the power supply.

[0052] The live wire L of the power supply is also connected to one end of the contact MP11 of the motor protector 2. The other end of the contact MP11 of the motor protector 2 is connected to one end of the coil KT1 of the first power-off delay relay 4. The other end of the coil KT1 of the first power-off delay relay 4 is connected to the neutral wire N of the power supply.

[0053] The live wire L of the power supply is also connected to one end of the normally open contact KT21 of the second power-off delay relay 5. The other end of the normally open contact KT21 of the second power-off delay relay 5 is connected to one end of the normally closed contact KT11 of the first power-off delay relay 4. The other end of the normally closed contact KT11 of the first power-off delay relay 4 is connected to one end of the coil KM1 of the contactor 3. The other end of the coil KM1 of the contactor 3 is connected to the neutral wire N of the power supply.

[0054] Embodiment 2

[0055] As Figure 2 shown in the schematic flow chart of the dual-power switching control method for preventing load power-off according to an embodiment of the present invention, as Figure 2 shown, the method includes the following steps:

[0056] Step 1: When the circuit is powered by the main power supply and is in a waiting state for startup operation, the normally closed contact KT11 of the first power-off delay relay 4 is closed, the normally open contact KT21 of the second power-off delay relay 5 is open, the coil KM1 of the contactor 3 is de-energized, the normally open main contact KM11 of the contactor 3 is open, and the load is in a stopped operation state;

[0057] Step 2: Perform corresponding startup operations according to the state of the local / remote switching switch SA; if local control is selected, close the local startup switch SB1, the coil KT2 of the second power-off delay relay 5 is energized, the normally open contact KT21 of the second power-off delay relay 5 is closed. After the normally open contact KT21 of the second power-off delay relay 5 is closed, the local startup switch SB1 can be disconnected, and the normally open contact KT21 of the second power-off delay relay 5 remains closed. The coil KM1 of the contactor 3 is energized, and the normally open main contact KM11 of the contactor 3 is closed to make the load operate; if remote control is selected, close the remote DCS startup contact SBR, the coil KT2 of the second power-off delay relay 5 is energized, the normally open contact KT21 of the second power-off delay relay 5 is closed. After the normally open contact KT21 of the second power-off delay relay 5 is closed, the remote DCS startup contact SBR can be disconnected, and the normally open contact KT21 of the second power-off delay relay 5 remains closed. The coil KM1 of the contactor 3 is energized, and the normally open main contact KM11 of the contactor 3 is closed to make the load operate;

[0058] Step 3.1: During the operation of the load, if the coil MP1 of the motor protector 2 detects a fault in the load circuit, the contact MP11 of the motor protector 2 closes, the coil KT1 of the first power-off delay relay 4 is energized, the normally closed contact KT11 of the first power-off delay relay 4 opens, the coil KT2 of the second power-off delay relay 1 loses power, and at the same time, the coil KM1 of the contactor 3 loses power. The normally open main contact KM11 of the contactor 3 opens, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay 4 opens, the contact MP11 of the motor protector 2 can be disconnected. The normally closed contact KT11 of the first power-off delay relay 4 remains open for a preset duration, the coil KT2 of the second power-off delay relay 1 remains de-energized, and the timing starts. When the timing reaches the preset duration, the normally open contact KT21 of the second power-off delay relay 5 opens, the coil KM1 of the contactor 3 remains de-energized, and the normally open main contact KM11 of the contactor 3 remains open, causing the load to remain stopped.

[0059] Step 3.2: During the operation of the load, perform corresponding stop operations according to the status of the remote / local changeover switch SA; if local control is selected, close the local stop switch SB2, the coil KT1 of the first power-off delay relay 4 is energized, the normally closed contact KT11 of the first power-off delay relay 4 is disconnected, the coil KT2 of the second power-off delay relay 1 is de-energized, and at the same time, the coil KM1 of the contactor 3 is de-energized, and the normally open main contact KM11 of the contactor 3 is disconnected, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay 4 is disconnected, the local stop switch SB2 can be disconnected. The normally closed contact KT11 of the first power-off delay relay 4 remains disconnected for a preset duration, the coil KT2 of the second power-off delay relay 1 remains de-energized, and the timing starts; when the timing time reaches the preset duration, the normally open contact KT21 of the second power-off delay relay 5 is disconnected, the coil KM1 of the contactor 3 remains de-energized, and the normally open main contact KM11 of the contactor 3 remains disconnected, causing the load to remain stopped; if remote control is selected, close the remote DCS stop contact SBS, the coil KT1 of the first power-off delay relay 4 is energized, the normally closed contact KT11 of the first power-off delay relay 4 is disconnected, the coil KT2 of the second power-off delay relay 1 is de-energized, and at the same time, the coil KM1 of the contactor 3 is de-energized, and the normally open main contact KM11 of the contactor 3 is disconnected, causing the load to stop running. After the normally closed contact KT11 of the first power-off delay relay 4 is disconnected, the remote DCS stop contact SBS can be disconnected. The normally closed contact KT11 of the first power-off delay relay 4 remains disconnected for a preset duration, the coil KT2 of the second power-off delay relay 1 remains de-energized, and the timing starts; when the timing time reaches the preset duration, the normally open contact KT21 of the second power-off delay relay 5 is disconnected, the coil KM1 of the contactor 3 remains de-energized, and the normally open main contact KM11 of the contactor 3 remains disconnected, causing the load to remain stopped;

[0060] Step 3.3: During the operation of the load, when the load power supply is switched, the entire circuit will lose power for a short time. The coil KM1 of the contactor 3 loses power, and the normally open main contact KM11 of the contactor 3 disconnects, and the load enters the stop operation state. At the same time, the coil KT2 of the second power-off delay relay 5 loses power, and the normally open contact KT21 of the second power-off delay relay 5 remains closed and starts timing; within the timing time, the load power supply switching is completed, and the coil KM1 of the contactor 3 is powered through the normally open contact KT21 of the second power-off delay relay 5 that remains closed, and the normally open main contact KM11 of the contactor 3 closes, enabling the load to resume operation; after the coil KT2 of the second power-off delay relay 5 is powered, it resets and stops timing, and the normally open contact KT21 of the second power-off delay relay 5 remains closed to ensure the continuous operation of the load and prevent the load from stopping running after a short power loss during the power supply switching. The normally closed contact KT11 of the first power-off delay relay 4 delays for a preset duration longer than the preset duration of the normally open contact KT21 of the second power-off delay relay 5; the preset duration of the normally open contact KT21 of the second power-off delay relay 5 is longer than the load power supply switching duration.

[0061] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A load protection circuit for dual power supply switching, comprising a load circuit and a control circuit, wherein the load circuit comprises: A dual power switching module (1), a motor protector (2), and a contactor (3); the dual power switching module (1) is used to control the access status of a main power supply and a backup power supply, wherein the main power supply and the backup power supply are not accessed at the same time; the motor protector (2) is used to monitor the state of the load circuit and to predict and protect the load circuit from failure; the contactor (3) is used to control the start or stop of the load; and the characteristics are: The control circuit comprises: a remote local switch SA, a remote DCS stop contact SBS, a remote DCS start contact SBR, a local stop switch SB2, a local start switch SB1, a first power-off delay relay (4), and a second power-off delay relay (5); The remote local switch SA is used to switch remote or local control. When switched to local control, it controls the control circuits of the local stop switch SB2 and the local start switch SB1. When switched to remote control, it controls the control circuits of the remote DCS stop contact SBS and the remote DCS start contact SBR. The remote DCS stop contact SBS is used to control the disconnection of the power supply of the first power-off delay type relay (4) according to the stop operation of the remote DCS; The remote DCS start contact SBR is used to control the power supply of the first power-off delay type relay (4) according to the start operation of the remote DCS; The local stop switch SB2 is used to control the disconnection of the power supply of the first power-off delay type relay (4) according to the local stop operation; The local starting switch SB1 is used to control the power supply of the first power-off delay type relay (4) according to the local starting operation; The first power-off delay relay (4) is used to control the power supply of the contactor (3) to be turned on according to any one of the starting operations of the remote DCS starting contact SBR or the starting operation of the local starting switch SB1, so that the load can run; and to control the power supply of the contactor (3) to be turned off according to any one of the stopping operations of the remote DCS stopping contact SBS or the stopping operation of the local stopping switch SB2 or the protection action of the motor protector (2), so that the load can stop running, and to maintain the preset time length to prevent the load from resuming operation immediately after the stopping operation disappears; The second power-off delay relay (5) is used to keep the energized circuit of the contactor (3) connected during the switching process of the dual power switching module (1), and to restore the energized state of the contactor (3) after the switching of the dual power switching module (1) is completed, so as to avoid instantaneous power failure of the load during power switching.

2. The load protection circuit for dual power supply switching according to claim 1, characterized in that: One end of the dual power switching module (1) is connected to a main power supply or a backup power supply, the other end of the dual power switching module (1) is connected to one end of a normally open main contact KM11 of the contactor (3), the other end of the normally open main contact KM11 of the contactor (3) is connected to one end of a coil MP1 of the motor protector (2), and the other end of the coil MP1 of the motor protector (2) is connected to a load.

3. The load protection circuit for dual power supply switching according to claim 2, characterized in that: The power live wire L is connected to one end of the remote local switch SA, and the other end of the remote local switch SA is respectively connected to one end of the remote DCS stop contact SBS, the remote DCS start contact SBR, the local stop switch SB2, and the local start switch SB1.

4. The load protection circuit for dual power supply switching according to claim 3, characterized in that: The other end of the remote DCS stop contact SBS and the local stop switch SB2 is connected to one end of the coil KT1 of the first power-off delay relay (4), and the other end of the coil KT1 of the first power-off delay relay (4) is connected to the neutral line N of the power supply.

5. The load protection circuit for dual power supply switching according to claim 4, characterized in that: The other end of the remote DCS starting contact SBR and the local starting switch SB1 are connected to one end of the normally closed contact KT11 of the first power-off delay relay (4), the other end of the normally closed contact KT11 of the first power-off delay relay (4) is connected to one end of the coil KM1 of the contactor (3), and the other end of the coil KM1 of the contactor (3) is connected to the neutral line N of the power supply.

6. According to the load protection circuit for dual power switching as described in claim 5, the coil KT2 of the second power-off delay relay (1) is connected in parallel between the other end of the normally closed contact KT11 of the first power-off delay relay (4) and the neutral line N phase of the power supply.

7. According to the load protection circuit for dual power switching as described in claim 6, the live wire L of the power supply is also connected to one end of the contact MP11 of the motor protector (2), the other end of the contact MP11 of the motor protector (2) is connected to one end of the coil KT1 of the first power-off delay relay (4), and the other end of the coil KT1 of the first power-off delay relay (4) is connected to the neutral wire N of the power supply.

8. According to the load protection circuit for dual power switching as described in claim 7, the power live wire L is also connected to one end of the normally open contact KT21 of the second power-off delay relay (5), the other end of the normally open contact KT21 of the second power-off delay relay (5) is connected to one end of the normally closed contact KT11 of the first power-off delay relay (4), the other end of the normally closed contact KT11 of the first power-off delay relay (4) is connected to one end of the coil KM1 of the contactor (3), and the other end of the coil KM1 of the contactor (3) is connected to the neutral wire N of the power supply.

9. A load protection method for dual power supply switching, characterized in that: The steps include: When the circuit is powered by the main power supply and is in a waiting state for the start operation, the normally closed contact KT11 of the first power-off delay type relay (4) is closed, the normally open contact KT21 of the second power-off delay type relay (5) is disconnected, the coil KM1 of the contactor (3) loses power, the normally open main contact KM11 of the contactor (3) is disconnected, and the load is in a stopped operation state; According to the state of the remote local switching switch SA, the corresponding starting operation is performed; if local control is selected, the local starting switch SB1 is closed, the coil KT2 of the second power-off delay type relay (5) is energized, and the normally open contact KT21 of the second power-off delay type relay (5) is closed. When the normally open contact KT21 of the second power-off delay type relay (5) is closed, the local starting switch SB1 can be disconnected, the normally open contact KT21 of the second power-off delay type relay (5) remains closed, the coil KM1 of the contactor (3) is energized, and the normally open main contact KM1 of the contactor (3) is closed. 1 is closed to make the load run; if remote control is selected, the remote DCS start contact SBR is closed, the coil KT2 of the second power-off delay relay (5) is energized, and the normally open contact KT21 of the second power-off delay relay (5) is closed. When the normally open contact KT21 of the second power-off delay relay (5) is closed, the remote DCS start contact SBR can be disconnected, and the normally open contact KT21 of the second power-off delay relay (5) remains closed, the coil KM1 of the contactor (3) is energized, and the normally open main contact KM11 of the contactor (3) is closed to make the load run; During the operation of the load, if the coil MP1 of the motor protector (2) detects that a fault has occurred in the load circuit, the contact MP11 of the motor protector (2) is closed, the coil KT1 of the first power-off delay relay (4) is energized, the normally closed contact KT11 of the first power-off delay relay (4) is disconnected, the coil KT2 of the second power-off delay relay (1) is de-energized, and at the same time the coil KM1 of the contactor (3) is de-energized, the normally open main contact KM11 of the contactor (3) is disconnected, and the load stops running. When the first power-off delay relay ( After the normally closed contact KT11 of the contactor (4) is disconnected, the contact MP11 of the motor protector (2) can be disconnected, the normally closed contact KT11 of the first power-off delay relay (4) remains disconnected for a preset time, the coil KT2 of the second power-off delay relay (1) remains de-energized, and timing begins; when the timing reaches the preset time, the normally open contact KT21 of the second power-off delay relay (5) is disconnected, the coil KM1 of the contactor (3) remains de-energized, and the normally open main contact KM11 of the contactor (3) remains disconnected, so that the load remains stopped; During the operation of the load, the corresponding stop operation is performed according to the state of the remote local switching switch SA; if local control is selected, the local stop switch SB2 is closed, the coil KT1 of the first power-off delay relay (4) is energized, the normally closed contact KT11 of the first power-off delay relay (4) is disconnected, the coil KT2 of the second power-off delay relay (1) is de-energized, and at the same time the coil KM1 of the contactor (3) is de-energized, the normally open main contact KM11 of the contactor (3) is disconnected, and the load stops running. After the normally closed contact KT11 of a power-off delay relay (4) is disconnected, the local stop switch SB2 can be disconnected, the normally closed contact KT11 of the first power-off delay relay (4) remains disconnected for a preset time, the coil KT2 of the second power-off delay relay (1) remains de-energized, and timing begins; when the timing reaches the preset time, the normally open contact KT21 of the second power-off delay relay (5) is disconnected, the coil KM1 of the contactor (3) remains de-energized, and the normally open main contact KM11 of the contactor (3) is closed. The load is kept disconnected and stopped; if remote control is selected, the remote DCS stop contact SBS is closed, the coil KT1 of the first power-off delay relay (4) is energized, the normally closed contact KT11 of the first power-off delay relay (4) is disconnected, the coil KT2 of the second power-off delay relay (1) is de-energized, and at the same time, the coil KM1 of the contactor (3) is de-energized, the normally open main contact KM11 of the contactor (3) is disconnected, and the load stops running. When the normally closed contact of the first power-off delay relay (4) is closed, the coil KT2 of the second power-off delay relay (1) is de-energized. At the same time, the coil KM1 of the contactor (3) is de-energized, and the normally open main contact KM11 of the contactor (3) is disconnected, the load stops running. After KT11 is disconnected, the remote DCS stop contact SBS is disconnected, the normally closed contact KT11 of the first power-off delay relay (4) remains disconnected for a preset time, the coil KT2 of the second power-off delay relay (1) remains de-energized, and timing begins; when the timing reaches the preset time, the normally open contact KT21 of the second power-off delay relay (5) is disconnected, the coil KM1 of the contactor (3) remains de-energized, and the normally open main contact KM11 of the contactor (3) remains disconnected, so that the load remains stopped; During the operation of the load, when the load power supply is switched, the entire circuit will lose power for a short time, the coil KM1 of the contactor (3) will lose power, the normally open main contact KM11 of the contactor (3) will be disconnected, the load will enter a stopped operation state, and the coil KT2 of the second power-off delay type relay (5) will lose power at the same time, the normally open contact KT21 of the second power-off delay type relay (5) will remain closed, and timing will start; within the timing time, the load power supply switching is completed, the coil KM1 of the contactor (3) will be energized by maintaining the normally open contact KT21 of the second power-off delay type relay (5) closed, and the normally open main contact KM11 of the contactor (3) will be closed, so that the load will resume operation; after the coil KT2 of the second power-off delay type relay (5) is energized, the timing is reset and stopped, and the normally open contact KT21 of the second power-off delay type relay (5) will remain closed, ensuring the continuous operation of the load and avoiding the load from stopping operation after a short power failure during power supply switching.

10. The load protection method for dual power supply switching according to claim 9, characterized in that: The preset delay time length of the normally closed contact KT11 of the first power-off delay relay (4) is longer than the preset delay time length of the normally open contact KT21 of the second power-off delay relay (5); the preset delay time length of the normally open contact KT21 of the second power-off delay relay (5) is longer than the load power supply switching time length.

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