Molded case controller and current signal conditioning circuit thereof

Abstract

The utility model discloses a molded case controller and a current signal conditioning circuit thereof. The current signal conditioning circuit is connected in series between a current transformer and a microprocessor of a molded case controller, and comprises a primary amplification circuit, a filter circuit and a secondary amplification circuit which are connected in series, the output end of the primary amplification circuit is the first output end of the current signal conditioning circuit, the primary amplification circuit is connected with the microprocessor, and a sampling signal outputs a primary amplification signal to the microprocessor through the primary amplification circuit; the output end of the secondary amplification circuit is the second output end of the current signal conditioning circuit, the secondary amplification circuit is connected with the microprocessor, and the primary amplification signal passes through the filter circuit and the secondary amplification circuit to output a secondary amplification signal to the microprocessor. Through the current signal conditioning circuit, the measurement range of the current can be expanded, the precision of low-current measurement is improved, and the protection requirement of low-current setting gears is met.

Description

Technical Field

[0001] The utility model relates to the field of molded case controllers, in particular to a molded case controller and a current signal conditioning circuit thereof. Background Art

[0002] The molded case controller is an electrical device used to implement four protection functions: long delay overload, short delay short circuit, instantaneous short circuit and ground fault.

[0003] The current sampling of the existing molded case controller generally has only one-stage amplification circuit, the signal amplification factor is fixed, the small current measurement accuracy is poor, and it cannot meet the overload protection requirements of the small current setting gear. Utility Model Content

[0004] In view of the above-mentioned defects in the prior art, the utility model provides a current signal conditioning circuit of a molded case controller, which can improve the measurement accuracy of small currents and meet the overload protection requirements of small current setting gears.

[0005] The technical solution is as follows:

[0006] A current signal conditioning circuit of a molded case controller is connected in series between a current transformer and a microprocessor of the molded case controller, and comprises a primary amplifying circuit, a filtering circuit and a secondary amplifying circuit connected in series;

[0007] The output end of the primary amplifier circuit is the first output end of the current signal conditioning circuit, which is connected to the microprocessor, and the sampling signal is output through the primary amplifier circuit to output a primary amplified signal to the microprocessor;

[0008] The output end of the secondary amplifier circuit is the second output end of the current signal conditioning circuit, which is connected to the microprocessor. The primary amplified signal passes through the filter circuit and the secondary amplifier circuit to output a secondary amplified signal to the microprocessor.

[0009] Further, the primary amplifier circuit is a second-order multi-terminal negative feedback amplifier circuit, comprising: a first operational amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, and a second capacitor;

[0010] The input end of the current signal conditioning circuit is connected to the negative input end of the first operational amplifier through a first resistor, a second resistor, and is connected to the output end of the first operational amplifier through a first resistor, a third resistor, and is connected to a signal ground through a first resistor, a first capacitor; the output end of the first operational amplifier is connected to the negative input end of the first operational amplifier through a second capacitor; and the positive input end of the first operational amplifier is connected to the signal ground.

[0011] Furthermore, the filter circuit is a first-order RC filter circuit, including: a fourth resistor and a third capacitor; the input end of the filter circuit is connected to the output end of the filter circuit through the fourth resistor, and the output end of the filter circuit is connected to the signal ground through the third capacitor.

[0012] Furthermore, the secondary amplifier circuit is a common-phase amplifier circuit, including a second operational amplifier, a fifth resistor and a sixth resistor; the positive input terminal of the second operational amplifier is the input terminal of the common-phase amplifier circuit; the negative input terminal of the second operational amplifier is connected to the signal ground through the fifth resistor, and is connected to the output terminal of the second operational amplifier through the sixth resistor; the output terminal of the second operational amplifier is the output terminal of the common-phase amplifier circuit.

[0013] The utility model also provides a plastic shell controller, and the technical solution is as follows:

[0014] A molded case controller comprises: a current transformer, a microprocessor and a sampling circuit; the sampling circuit is the current signal conditioning circuit as described above, the input end of the current signal conditioning circuit is connected to the current transformer, and the first output end and the second output end of the current signal conditioning circuit are respectively connected to an AD input pin of the microprocessor.

[0015] Furthermore, the microprocessor is a 32-bit ARM processor.

[0016] Furthermore, the molded case controller also includes a coding switch; the coding switch is connected to the microprocessor and is used to set the setting gear of the protection current and time.

[0017] Furthermore, the molded case controller also includes: a voltage stabilizing circuit, a rectifying and discharging circuit, a mutual inductance power taking circuit, a tripping circuit, an alarm indicating circuit, a communication module, a current transformer and a magnetic release;

[0018] The mutual inductance power supply circuit is connected to the current transformer, and is used to take power from at least one of the power supply lines of each phase of the molded case controller, and generate multiple DC power supplies through the rectification and leakage circuit and the voltage stabilizing circuit to supply power to the microprocessor, the tripping circuit, the alarm indication circuit, and the communication module;

[0019] The tripping circuit is connected to the flux tripper and is used to perform a tripping operation according to the instruction of the microprocessor;

[0020] The communication module is connected to the microprocessor and is used for communication between the microprocessor and a host computer.

[0021] The utility model achieves the following technical effects:

[0022] The current signal conditioning circuit adopts a series-connected two-stage amplifier circuit to perform graded amplification and output of the sampling signal, which can expand the current measurement range and improve the small current measurement accuracy, thereby meeting the overload protection requirements of the small current setting gear of the molded case controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the circuit diagram of the molded case controller;

[0024] Figure 2 The utility model is a circuit principle diagram of a current signal conditioning circuit. DETAILED DESCRIPTION

[0025] To further illustrate each embodiment, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in this field should be able to understand other possible implementations and advantages of the present invention.

[0026] The utility model is now further described in conjunction with the accompanying drawings and specific implementation methods.

[0027] like Figure 1 and Figure 2 As shown, the molded case controller includes a shell, a processor circuit, a voltage stabilizing circuit, a rectifying and discharging circuit, a mutual inductance power supply circuit, a sampling circuit, a tripping circuit, an alarm indication circuit, a communication module and other circuits, as well as actuators such as a current transformer and a flux release.

[0028] In this embodiment, the processor circuit collects the current of each phase A / B / C / N of the circuit breaker through a current transformer, generates a 12V power supply for the tripping circuit through a rectification and leakage circuit, and generates a 3.3V power supply for the processor circuit, communication module, operational amplifier circuit and other circuits through a secondary voltage stabilizing circuit.

[0029] After the current sampling signal of the current transformer is processed by the sampling circuit, the processor circuit collects the current value of each phase, and reads the protection current and time setting value of each section corresponding to the coding switch in real time. The processor circuit performs calculations based on the current and the corresponding setting value, and issues the corresponding tripping or alarm instructions according to the tripping current and time agreement required by the technical requirements, so that the tripping circuit is activated, the flux release is tripped, the main circuit power supply is disconnected, or the corresponding sound and light alarm is issued.

[0030] In this embodiment, the communication module adopts a standard RS485 interface and ModBus-RTU protocol, which can realize functions such as remote real-time viewing of current, fault records and setting value data, remote opening, communication test tripping, etc.

[0031] In this embodiment, an embodiment of a single-phase sampling circuit using a multi-stage amplifier circuit is provided. The sampling circuit is composed of a series-connected MFB (multi-terminal negative feedback) amplifier circuit, a filter circuit, and a common-phase amplifier circuit, and is also referred to as a current signal conditioning circuit. The specific circuit is as follows Figure 2 shown.

[0032] In this embodiment, a second-order MFB amplifier circuit is used, which is composed of an operational amplifier U3A, resistors R12, R13, R14, capacitors C11, C12, and a filter capacitor C10. The sampling signal IIA is output through the MFB amplifier circuit as a primary amplified signal HCS_AD0 to the microprocessor U1, and the primary amplified signal HCS_AD0 is also used as the input of the next-stage filter circuit and the in-phase amplifier circuit.

[0033] In this embodiment, the filter circuit adopts a first-order RC filter circuit, which is composed of a resistor R41 and a capacitor C41. The in-phase amplifier circuit is composed of an operational amplifier U5A, resistors R42, R43 and a capacitor C40. R42 is connected between the negative input terminal and the signal ground of U5A, R43 is connected between the negative input terminal and the output terminal of U5A, and C40 is a power supply filter capacitor. The primary amplified signal HCS_AD0 is output through the filter circuit and the in-phase amplifier circuit to the secondary amplified signal CS_AD0 to the microprocessor U1.

[0034] In this embodiment, the operational amplifiers U3A, U5A and the microprocessor U1 are all powered by the system power supply DVDD. Preferably, the voltage of DVDD is 3.3V.

[0035] In this embodiment, the processor circuit uses a 32-bit ARM processor as a core processor unit, namely, the microprocessor U1.

[0036] The microprocessor U1 can automatically identify the primary amplified signal HCS_AD0 and the secondary amplified signal CS_AD0 according to the amplitude of the primary amplified signal HCS_AD0 and the secondary amplified signal CS_AD0. When the sampled current is large, the primary amplified signal HCS_AD0 is selected, and when the sampled current is small, the secondary amplified signal CS_AD0 is selected. Through this current signal conditioning circuit, the current measurement range can be expanded, the accuracy of small current measurement can be improved, and the protection requirements of small current setting gears can be met.

[0037] Although the present invention has been specifically demonstrated and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes may be made to the present invention in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A current signal conditioning circuit for a molded case controller, characterized in that: The current signal conditioning circuit is connected in series between the current transformer and the microprocessor of the molded case controller, and includes a primary amplification circuit, a filter circuit and a secondary amplification circuit connected in series; The output end of the primary amplifier circuit is the first output end of the current signal conditioning circuit, which is connected to the microprocessor, and the sampling signal is output through the primary amplifier circuit to output a primary amplified signal to the microprocessor; The output end of the secondary amplifier circuit is the second output end of the current signal conditioning circuit, which is connected to the microprocessor. The primary amplified signal passes through the filter circuit and the secondary amplifier circuit to output a secondary amplified signal to the microprocessor.

2. The current signal conditioning circuit according to claim 1, characterized in that: The primary amplifier circuit is a second-order multi-terminal negative feedback amplifier circuit, comprising: a first operational amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, and a second capacitor; The input end of the current signal conditioning circuit is connected to the negative input end of the first operational amplifier through a first resistor, a second resistor, and is connected to the output end of the first operational amplifier through a first resistor, a third resistor, and is connected to a signal ground through a first resistor, a first capacitor; the output end of the first operational amplifier is connected to the negative input end of the first operational amplifier through a second capacitor; and the positive input end of the first operational amplifier is connected to the signal ground.

3. The current signal conditioning circuit according to claim 1, characterized in that: The filter circuit is a first-order RC filter circuit, including: a fourth resistor and a third capacitor; the input end of the filter circuit is connected to the output end of the filter circuit through the fourth resistor, and the output end of the filter circuit is connected to the signal ground through the third capacitor.

4. The current signal conditioning circuit according to claim 1, characterized in that: The secondary amplifier circuit is a common-phase amplifier circuit, including a second operational amplifier, a fifth resistor and a sixth resistor; the positive input terminal of the second operational amplifier is the input terminal of the common-phase amplifier circuit; the negative input terminal of the second operational amplifier is connected to the signal ground through the fifth resistor, and is connected to the output terminal of the second operational amplifier through the sixth resistor; the output terminal of the second operational amplifier is the output terminal of the common-phase amplifier circuit.

5. The current signal conditioning circuit according to claim 1, characterized in that: The power supply voltage of the current signal conditioning circuit is 3.3V.

6. A plastic shell controller, characterized in that: include: Current transformer, microprocessor and sampling circuit; The sampling circuit is the current signal conditioning circuit according to any one of claims 1 to 5, the input end of the current signal conditioning circuit is connected to the current transformer, and the first output end and the second output end of the current signal conditioning circuit are respectively connected to an AD input pin of the microprocessor.

7. The molded case controller according to claim 6, characterized in that: The microprocessor is a 32-bit ARM processor.

8. The molded case controller according to claim 6, characterized in that: The molded case controller also includes a coding switch; the coding switch is connected to the microprocessor and is used to set the setting gear of the protection current and time.

9. The molded case controller according to claim 6, characterized in that: The molded case controller also includes: a voltage stabilizing circuit, a rectifying and discharging circuit, a mutual inductance power taking circuit, a tripping circuit, an alarm indicating circuit, a communication module, a current transformer and a magnetic release; The mutual inductance power supply circuit is connected to the current transformer, and is used to take power from at least one of the power supply lines of each phase of the molded case controller, and generate multiple DC power supplies through the rectification and leakage circuit and the voltage stabilization circuit to supply power to the microprocessor, the tripping circuit, the alarm indication circuit, and the communication module; The tripping circuit is connected to the flux tripper and is used to perform a tripping operation according to the instruction of the microprocessor; The communication module is connected to the microprocessor and is used for communication between the microprocessor and a host computer.

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