CN106771532B - Method and circuit for testing instantaneous current of leakage protector - Google Patents
Method and circuit for testing instantaneous current of leakage protector Download PDFInfo
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- CN106771532B CN106771532B CN201710080142.7A CN201710080142A CN106771532B CN 106771532 B CN106771532 B CN 106771532B CN 201710080142 A CN201710080142 A CN 201710080142A CN 106771532 B CN106771532 B CN 106771532B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/22—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using conversion of ac into dc
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
Abstract
The invention discloses a method and a circuit for testing instantaneous current of a leakage protector, wherein the testing method adopts a testing circuit connected with an input end and an output end of the leakage protector, and the testing circuit comprises a rectifying unit, one or two testing keys, a current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current; when the test key is pressed, the current unit generates an analog leakage current, and the analog leakage current is automatically cut off by the cut-off unit after lasting 0.1 to 0.2 seconds. The instantaneous current testing circuit of the leakage protector adopts electronic elements with smaller power, so that the reliability and miniaturization of the circuit are improved, the state of the leakage protector is tested to be good, and the tripping response sensitivity of the leakage protector can be tested. The invention can be implemented on a single test key circuit of a common leakage protector, and also can be implemented on a leakage protector provided with a double test key circuit.
Description
Technical Field
The invention relates to an electric leakage protector for electric power safety equipment, belongs to the field of low-voltage electrical appliances, and particularly relates to an instantaneous current testing method and an instantaneous current testing circuit for the electric leakage protector.
Background
In the conventional power distribution system, the earth leakage protector is the most effective equipment for preventing personal electric shock accidents, so that it is now seemingly possible to install the earth leakage protector at every place where electricity is used. However, the electric leakage protector is not absolutely safe or always safe after installation, and when the electric leakage protector is damaged as other electric appliances, or the tripping action of the electric leakage protector with a safety protection function is slow due to aging, if the electric leakage protector is not subjected to frequent function inspection, once the electric leakage protector fails, the electric leakage tripping protection action of the electric leakage protector cannot be effectively implemented, and dangerous electric shock accidents are easy to happen. Referring to fig. 1, the existing leakage protector function checking method simulates a leakage current to flow through an electrical bypass between an input end power supply and an output end power supply of the leakage protector, the current can unbalance a zero sequence transformer inside the leakage protector, and if the current reaches a rated trip current amount (generally 30 mA), the leakage protector trips.
According to the 39 th rule of the 'safety supervision of leakage protector' issued by the national ministry of labor 1990, the leakage protector in operation must be checked at least once every month, and the quality of the leakage protector is tested, and ensures the safety of electricity.
As shown in fig. 1, the current household leakage protector RCD has a normally open test button 7 (referred to herein as a test button), and is connected in series with a current limiting resistor 6, and both ends of the current limiting resistor are connected to the terminals of the input power source 1 and the output power source 5 of the leakage protector, once the test button 7 is triggered, the 30mA analog leakage current flowing through the button and the resistor increases the current difference between the live wire and the zero wire inside the leakage protector by 30mA, the zero sequence transformer 4 is severely unbalanced, the unbalanced electrical signal is amplified by the amplifier 3, the current flows into the electromagnetic coil of the detacher 2 to generate a strong magnetic field, the magnetic field pulling force makes the detacher loosen the contact point carrying the power source, and the leakage protector trips accordingly.
Once any one test button of the existing leakage protector is pressed, the simulated leakage current continuously flows until the test button is released, the time length of the simulated leakage current follows the time length of the pressed test button, and the time length can be unequal from 0.1 to 2 seconds, even longer, and the current can not be controlled at all, so that the tripping response sensitivity of the leakage protector can not be detected. In order for the earth leakage protector to effectively drive the trip action, the analog earth leakage current value needs to be higher than 30mA, which causes thermal power consumption of at least 6.6W, and the circuit therefore needs to use a large-sized high-power resistor to prevent burnout, and a large space is also required for installing the large-sized resistor. As shown in fig. 2, once the second test button of the leakage protector is pressed, the analog leakage current continues to flow between the live wire and the neutral wire until the test button is released, and the analog leakage current needs to be increased to about 15mA for testing the operation stability of the leakage protector, which causes the thermal power consumption to be at least 3.3W, and the circuit also needs to use a large-sized high-power resistor to prevent burnout, and a large space is required for installing the large-sized resistor.
The dual test circuit shown in fig. 2 also cannot accurately control the length of time for leakage generated by the first and second test circuits, and the duration of the simulated leakage current is completely determined by the time for the field user to manually press the test button, which can be as long as several seconds. Pressing the first test circuit does not allow the user to know whether his earth leakage protector can trip within 0.1 seconds or less. Also because the length of time the leakage generated by the first and second test circuits cannot be controlled, the leakage protector manufacturer only has to select a large high power resistor to avoid component burnout when the user tests the leakage protector.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an instantaneous current test circuit of a leakage protector formed by electronic elements with smaller power and a test method using the same, which can increase the reliability and miniaturization of the circuit, test whether the state of the leakage protector is good or not, and test the tripping response sensitivity of the leakage protector.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the test method adopts a test circuit connected with the input end and the output end of the leakage protector, and the test circuit comprises a rectifying unit, one or two test keys, a current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current; when the test key is pressed, the current unit generates an analog leakage current, and the current value of the analog leakage current is determined by the input voltage of the leakage protector and the current limiting resistance of the current unit; the simulated leakage current is automatically cut off by the cut-off unit after lasting 0.1 to 0.2 seconds; the rectification unit converts alternating current input by the leakage protector into direct current, and two alternating current input ends of the rectification unit are respectively connected with a power input end and an output end of the leakage protector; the test keys are connected to the direct-current output end of the rectifying unit, and when two test keys exist, the two test keys are in parallel connection; the current unit is provided with a current limiting resistor which is connected with the test key in series.
The test circuit in the leakage protector instantaneous current test method comprises a bridge rectifier and a first test circuit, wherein two alternating current input pins of the bridge rectifier are respectively connected with a power input end and an output end of the leakage protector, one pin is connected with a zero line, and the other pin is connected with a live line; the first test circuit comprises a first test key, a first current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current, one end of the first test key is connected with the positive pin of the bridge rectifier, and the other end of the first test key is marked as an M1 end; the input end of the first current unit is marked as an N1 end and the input end of the intercepting unit is marked as a K end, the output end of the first current unit is connected with the output end of the intercepting unit to form a common output end, the common output end is marked as a COM end, the M1 end is connected with the N1 end, and the COM end is connected with the negative pin of the bridge rectifier; when a first test key is pressed, the first current unit generates an analog leakage current which is larger than or equal to 30mA, and the analog leakage current is automatically cut off by the cut-off unit after lasting 0.1 to 0.2 seconds.
The first current unit comprises a first resistor and a first triode, one end of the first resistor is connected with the N1 end, and the other end of the first resistor is connected with the collector electrode of the first triode; the shutoff unit comprises a capacitor, a voltage stabilizing diode and a second triode, wherein one end of the capacitor is marked as an X end and is connected with the K end, and the other end of the capacitor is connected with the COM end; the negative electrode of the voltage stabilizing diode is connected with the X end of the capacitor, and the positive electrode of the voltage stabilizing diode is connected with the base electrode of the second triode; the collector electrode of the second triode is connected with the base electrode of the first triode and is connected with the N1 end together, and the emitter electrodes of the second triode and the first triode are connected with the COM end.
A first light emitting diode is connected between the N1 end and the first resistor.
The positive electrode of the voltage-stabilizing diode is connected with the COM, the collector of the second triode is connected with the K end, the sixth resistor is connected between the collector of the second triode and the base of the first triode, and the seventh resistor is connected between the collector of the second triode and the base of the first triode. The fourth resistor and the seventh resistor in the circuit are used for limiting the base currents of the second triode Q2 and the first triode Q1, and the fifth resistor is used for stabilizing the action of the second triode Q2.
The leakage protector instantaneous current test circuit also comprises a second test circuit, wherein the second test circuit comprises a second test key, a second current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current, one end of the second test key is connected with the positive pin of the bridge rectifier, the other end of the second test key is marked as an M2 end, and the shutoff unit of the second test circuit is shared with the shutoff unit of the first test circuit; the input end of the second current unit is connected with the M2 end, the output end of the second current unit is connected with the COM end, and when a second test key is pressed, the second current unit generates an analog leakage current with rated tripping current of 40-49.9%; the K end of the intercepting unit is connected with the M2 end.
The first current unit comprises a first resistor and a first triode, one end of the first resistor is connected with the N1 end, and the other end of the first resistor is connected with the collector electrode of the first triode; the second current unit comprises an eighth resistor and a first triode, the eighth resistor is connected between the K end and the input end of the first resistor, the intercepting unit comprises a capacitor, a zener diode and a second triode, one end of the capacitor is marked as an X end and is connected with the K end, and the other end of the capacitor is connected with the COM end; the negative electrode of the voltage stabilizing diode is connected with the X end of the capacitor, and the positive electrode of the voltage stabilizing diode is connected with the base electrode of the second triode; the collector of the second triode is connected with the base of the first triode and is connected with the K end together, and the emitter electrodes of the second triode and the first triode are connected with the COM end.
A first light emitting diode is connected between the M1 end and the N1 end, and a second light emitting diode is connected between the M2 end and the K end.
The positive electrode of the voltage-stabilizing diode is connected with the COM, the collector of the second triode is connected with the K end, the sixth resistor is connected between the collector of the second triode and the base of the first triode, and the seventh resistor is connected between the collector of the second triode and the base of the first triode. The fourth resistor and the seventh resistor in the circuit are used for limiting the base currents of the second triode Q2 and the first triode Q1, and the fifth resistor is used for stabilizing the action of the second triode Q2.
The first triode is replaced by a thyristor.
The first current unit comprises a first resistor and a first field effect transistor, one end of the first resistor is connected with the N1 end, and the other end of the first resistor is connected with the drain electrode of the first field effect transistor;
the second current unit comprises an eighth resistor and a first field effect transistor, and the eighth resistor is connected between the K end and the input end of the first resistor;
the shutoff unit comprises a capacitor, a first zener diode, a second zener diode and a second field effect transistor, wherein one end of the capacitor is marked as an X end and is connected with the K end, and the other end of the capacitor is connected with the COM end; the grid electrode of the second field effect transistor is connected with the X end of the capacitor; the second zener diode is connected in parallel with the two ends of the capacitor, and the cathode of the second zener diode is connected with the X end of the capacitor; the first zener diode is connected in parallel with the two ends of the second field effect transistor, and the cathode of the first zener diode is connected with the drain electrode of the second field effect transistor; the grid electrode of the first field effect tube is connected with the drain electrode of the second field effect tube and is connected with the K end together; the positive electrode of the first zener diode, the positive electrode of the second zener diode and the source electrode of the second field effect transistor are connected with the COM end;
the second resistor is connected between the K end and the X end of the capacitor, the third resistor is connected in parallel with the two ends of the capacitor, and the sixth resistor is connected with the drain electrode of the second field effect transistor and the K end.
According to the test method of the instantaneous current test circuit of the leakage protector, if the leakage protector has tripping reaction to the first test key before and does not react to the second test key, the leakage protector is normal in state, and the wiring and the load of the output end of the leakage protector are good.
According to the test method of the instantaneous current test circuit of the leakage protector, when the first test key SW1 in the first test circuit is pressed, as alternating voltage and current limiting resistance in the circuit are arranged at two ends of the circuit, analog leakage of about 30mA (effective value, RMS) occurs in the first test circuit, the duration of 30mA leakage current is between 0.1 and 0.2 seconds, equal current difference value is correspondingly generated between a live wire and a zero wire in the leakage protector, and as the current difference value reaches the trip rated leakage value (30 mA) of the leakage protector, the zero sequence transformer in the leakage protector is seriously unbalanced, and the tripping of the tripping device is triggered to cut off a power supply;
when the leakage protector is in normal operation and the second test button SW2 in the second test circuit is pressed, the AC power supply at two ends of the circuit and the current limiting resistor in the circuit generate an analog leakage, the current value of the analog leakage is 40% to 49.9% of the rated tripping current, the duration of the low-value leakage current is between 0.1 and 0.2 seconds, and the equal current difference value between the live wire and the zero wire in the leakage protector correspondingly occurs, but the current difference value does not reach half of the tripping rated leakage value (30 mA) of the leakage protector, so that the tripping action of the leakage protector without load cannot be generated.
If a small leakage to ground occurs in the wiring at the output end of the leakage protector or in the live wire of the electrical load, for example, 14mA, the simulated low-value leakage generated by triggering the second test key is added with the live wire leakage actually occurring in the wiring load, so that the current difference between the live wire and the zero wire in the leakage protector is correspondingly increased, and once the current difference approaches the tripping rated leakage value (30 mA), the leakage protector trips.
When the second test button SW2 is pressed to trigger a low value analog leakage current through the indicator lamp LED2, the LED2 is activated to indicate that the indicator lamp is turned off after a short time (between 0.1 and 0.2 seconds).
As shown in fig. 3, the first test button of the instantaneous current test circuit of the leakage protector, once triggered, simulates the circuit inside the matched leakage protector to generate a short-time (between 0.1 and 0.2 seconds) leakage with an effective value of 30mA, so that the leakage protector starts a tripping reaction and cuts off the output power supply. If the leakage protector does not react, the leakage protector is not sensitive and needs to be further checked.
As shown in FIG. 4, the second method of testing the key of the present invention is to connect a new similar circuit in parallel to the first test circuit of the instantaneous current test circuit of the leakage protector, which is called the second test circuit.
The second test circuit comprises a second test button which is normally open, once the second test button is pressed, a low-value simulated leakage current is generated, the leakage quantity is 40 to 49.9 percent of the rated tripping leakage current of the leakage protector, the leakage current lasts for a short time (between 0.1 and 0.2 seconds), if the output end of the leakage protector is not connected with any load, the tripping phenomenon occurs, the situation of the leakage protector is unstable, the sensitivity is too high, the misoperation is easy, and the further inspection is needed. If the normally good leakage protector is loaded and has a trip response to the second test button, this indicates that the load and its wiring have a small leakage present and further electrical inspection is required.
If the leakage protector has tripping reaction to the first test key before and has no reaction to the second test key, the leakage protector is in normal state, and the wiring and the load of the output end are good. In summary, we can know the following reliable and comprehensive leakage protector conditions according to the response of the tripping of the double test keys:
the invention also provides a test indicator lamp, the display test key is used for displaying the operation state, the test state of the leakage protector is displayed through the on or off of the indicator lamp, the first test key is pressed down, the LED1 lamp is on, the indicator lamp is off after a short time (between 0.1 and 0.2 seconds), the second test key is pressed down, the LED2 lamp is on, and the indicator lamp is off after a short time (between 0.1 and 0.2 seconds).
Compared with the prior art, the electric leakage protector instantaneous current test circuit adopting the technical scheme has the following beneficial effects:
the instantaneous current test circuit of the leakage protector can test whether the leakage protector can trip in time by using the electronic element to generate an instantaneous, transient and accurate analog leakage current, and can adopt the electronic element with smaller power, thereby improving the reliability and miniaturization of the circuit, and the test is more stable and accurate.
Drawings
Fig. 1: an internal circuit structure and a load wiring schematic diagram of a traditional single-phase leakage protector;
fig. 2: the internal structure of the leakage protector of the double-test circuit and the wiring schematic diagram of the load are shown;
fig. 3: the invention relates to a working schematic diagram of a single-key instantaneous current testing method of a leakage protector;
fig. 4: the invention relates to a working schematic diagram of a double bond instantaneous current testing method of a leakage protector;
fig. 5: the invention relates to a schematic diagram of a single-key instantaneous current testing circuit of a leakage protector, which uses a triode;
fig. 6: the double-bond instantaneous current testing circuit of the leakage protector uses a schematic diagram of a triode;
fig. 7: the double-bond instantaneous current testing circuit of the leakage protector uses a schematic diagram of a field effect transistor;
fig. 8: the invention relates to a schematic diagram of a single-key instantaneous current test circuit of a leakage protector, which uses a thyristor;
fig. 9: the double-bond instantaneous current testing circuit of the leakage protector uses a schematic diagram of a voltage comparator;
fig. 10: the double bond instantaneous test circuit of the leakage protector uses a schematic diagram of an MCU chip;
fig. 11: the double bond instantaneous test circuit of the leakage protector uses a schematic diagram of an LM555 chip;
fig. 12: the double-bond instantaneous test circuit of the leakage protector uses a principle diagram of 4016BD chip.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
Example 1: circuit using triode for leakage protector single-key instantaneous current test circuit
As shown in fig. 3 and 5, the test circuit is capable of generating an instantaneous trip analog leakage of greater than or equal to 30mA for a brief period of time of between 0.1 and 0.2 seconds. The circuit structure comprises a bridge rectifier BR1, two alternating current input pins of the bridge rectifier BR1 are connected with a zero line N1 of a power input end of the leakage protector and a live wire L2 of a power output end of the leakage protector (or connected with the live wire L1 of the power input end of the leakage protector and the zero line N2 of the power output end of the leakage protector), a negative (-) pin of the bridge rectifier BR1 is connected with a common loop point COM (also called a common end and a common connection point) of the whole circuit, a positive (+) pin of the bridge rectifier BR1 is connected with one end of a key SW1 (NO type), and the other end of the bridge rectifier BR1 is connected with an anode of a light emitting diode LED1, and is also connected with a common end of a sixth resistor R6 and a second resistor R2. The other end of the second resistor R2 is simultaneously connected with the third resistor R3, the fourth resistor R4 and the capacitor C. The third resistor R3 and the other end of the capacitor C are connected to the COM terminal. The other end of the fourth resistor R4 is connected with the cathode of the zener diode D3. The anode of the zener diode D3 is connected to one end of the fifth resistor R5 and the base b of the second triode Q2 at the same time. The emitter electrode e of the second triode Q2 and the other end of the fifth resistor R5 are connected to the COM end. The other end of the sixth resistor R6 is connected to the collector c of the second triode Q2 and the seventh resistor R7 at the same time. The other end of the seventh resistor R7 is connected with the base b of the first transistor Q1. The cathode of the first light emitting diode LED1 is connected with a first resistor R1, the other end of the first resistor R1 is connected with a collector electrode c of the first transistor Q1, and a radio electrode e of the first transistor Q1 is connected with a COM end. The ac input voltage is 220V, the resistance r1=6.8kΩ, r2=6.2mΩ, r3=1mΩ, r5=10mΩ, r6=400 kΩ, r7=200Ω, and the capacitance c=680 nF.
The electrical operation of the schematic diagram in block a in fig. 5 is explained as follows: in the initial period when the Normally Open (NO) button SW1 is pressed, the voltage of the capacitor C is zero volt, so that the second triode Q2 is in the cut-off state, and the ac power enters the base b of the first triode Q1 from the L2 and N1, through the bridge rectifier BR1, the test button SW1, the sixth resistor R6 and the seventh resistor R7, and the first triode Q1 is turned on. The first transistor Q1 is conducted to enable another current to appear, and the current flows from the alternating current power supply through the bridge rectifier BR1, the test key SW1, the test indicator light LED1 (the LED1 is lightened at the moment), the first resistor R1, the collector c of the first transistor Q1 and the radio electrode e of the first transistor Q1 to return to the common loop point COM end of the whole circuit. The first resistor R1 has a resistance of 6.8K ohms, so that its current value is 32mA (220 volts/6.8 ohms), i.e., the analog leakage current between L2 and N1 exceeds the trip rated current (30 mA) of the leakage protector. When the first transistor Q1 is turned on and current flows through R1, the third tiny current charges the capacitor C through the second resistor R2 to gradually increase the voltage of the capacitor C, and once the voltage exceeds the sum of the voltage stabilizing diode D3 and the Vbe (voltage of the base and the emitter electrode) turn-on voltage of the second transistor Q2, the second transistor Q2 enters a saturated conduction state, and also pulls down the Vbe voltage of the first transistor Q1, so that the first transistor Q1 returns to an cut-off state, cuts off the current of the first resistor R1, and cuts off the analog leakage current between L2 and N1. The analog leakage current generated by the circuit is transient, the time depends on the charging speed of the capacitor C, and the charging speed of the capacitor C mainly depends on the electrical parameters of the capacitor C, the second resistor R2, the third resistor R3 and the zener diode D3, and the time of the 30mA analog leakage current is set between 0.1 and 0.2 seconds.
Example 2: circuit using thyristor for single-key instantaneous current test circuit of leakage protector
As shown in fig. 3 and 8, this embodiment 2 is different from embodiment 1 in that the first transistor Q1 in embodiment 1 is replaced with a thyristor, where r2=1.2mΩ, r7=20Ω, and other electrical parameters of electronic components, and the wiring between electronic components is the same as that of embodiment 1.
Example 3: circuit using triode for double-key instantaneous current test circuit of leakage protector
As shown in fig. 4 and 6, the test circuit can generate two short-term analog leakage currents, the circuit structure comprises a bridge rectifier BR1, two ac input pins of the bridge rectifier BR1 are connected to a zero line N1 at a power input end of the leakage protector and a live wire L2 at a power output end of the leakage protector, a negative (-) pin of the bridge rectifier BR1 is connected to a common loop point COM (also called a common end, a common connection point) of the whole circuit, a positive (+) pin of the bridge rectifier BR1 is connected to a common end of a first key SW1 (NO type) and a second key SW2 (NO type), the other end of the bridge rectifier SW1 is connected to an anode of a light emitting diode LED1, and the other end of the bridge rectifier SW2 is connected to an anode of the light emitting diode LED 2. The cathode of the LED1 is connected with the common end of the first resistor R1 and the eighth resistor R8. The other end of the first resistor R1 is connected with the collector c of the first transistor Q1, and the emitter e of the first transistor Q1 is connected with the COM end. The other end of the eighth resistor R8 is connected with the cathode of the LED2, and is also connected with the second resistor R2 and the sixth resistor R6. The other end of the second resistor R2 is simultaneously connected with the third resistor R3, the fourth resistor R4 and the capacitor C, and the other ends of the third resistor R3 and the capacitor C are connected with the COM end. The other end of the fourth resistor R4 is connected with the cathode of the zener diode D3, the anode of the zener diode D3 is connected with the fifth resistor R5 and the base b of the second triode Q2, and the other end of the fifth resistor R5 and the emitter e of the second triode Q2 are connected with the COM end. The other end of the sixth resistor R6 is connected with the collector c of the second triode Q2 and the seventh resistor R7 at the same time, and the other end of the seventh resistor R7 is connected with the base b of the first triode Q1. The ac input voltage is 220V, the resistance r1=6.8kΩ, r2=6.2mΩ, r3=1mΩ, r5=10mΩ, r6=340 kΩ, r7=200Ω, r8=9.2kΩ, and the capacitance c=680 nF.
The electrical operation of the schematic diagram in block a in fig. 6 is explained as follows: SW1 and SW2 are two Normally Open (NO) keys, which are keys that trigger the start of the test. When SW1 is triggered, ac power flows from L2 and N1 through bridge rectifier BR1, test button SW1, test indicator LED1 (LED 1 is now on), eighth resistor R8, second resistor R2, and capacitor C is charged, and the voltage of C thus rises gradually from zero volts, but before this voltage reaches the sum of Vbe conduction voltages of zener diode D3 and second transistor Q2, second transistor Q2 is in an off state, which causes base b of first transistor Q1 to receive current through sixth resistor R6 and seventh resistor R7, and first transistor Q1 is thereby turned on into saturation. At this time, the current flowing through the collector c and the emitter electrode e of the first transistor Q1 is passed through the first resistor R1, and the current value thereof is 32mA (220 v/6.8K ohms). After 0.1 to 0.2 seconds, the voltage of the capacitor C increases to the sum of the Vbe conduction voltages of the zener diode D3 and the second transistor Q2, at this time, the second transistor Q2 is turned on to saturation, and the Vbe (the voltage of the base and the emitter) of the first transistor Q1 is also pulled down, so that the first transistor Q1 returns to the cut-off state, and the current of the first resistor R1 is cut off, i.e. the analog leakage current between L2 and N1 is cut off.
When the test button SW2 in fig. 6 is activated, the ac power flows from L2 and N1 through the bridge rectifier BR1, the test button SW2, the test indicator LED2 (LED 2 is lit at this time), the second resistor R2 and charges the capacitor C, and the voltage of the capacitor C gradually rises from zero volts, but before the voltage reaches the sum of the Vbe conduction voltages of the zener diode D3 and the second transistor Q2, the second transistor Q2 is in the off state, which causes the base b of the first transistor Q1 to obtain a current flowing through the sixth resistor R6 and the seventh resistor R7, and the first transistor Q1 is thereby turned on to enter the saturated state. At this time, the current flowing through the collector c and the emitter e of the first transistor Q1 is passed through the eighth resistor R8 and the first resistor R1 (total resistance 9.2k+6.8k=17K ohms), and the current value is 13mA (220 v/17K ohms). After 0.1 to 0.2 seconds, the voltage of the capacitor C increases to the sum of the Vbe conduction voltages of the zener diode D3 and the second transistor Q2, at this time, the second transistor Q2 is turned on to saturation, and the Vbe voltage of the first transistor Q1 is also pulled down, so that the first transistor Q1 returns to the cut-off state, and the currents of the eighth resistor R8 and the first resistor R1 are cut off, so that the analog leakage current between L2 and N1 is interrupted. The fourth resistor and the seventh resistor serve to limit the base currents of the second transistor Q2 and the first transistor Q1, and the fifth resistor stabilizes the action of the second transistor Q2.
Embodiment four: circuit using field effect transistor for double-bond instantaneous current test circuit of leakage protector
As shown in fig. 4 and 7, the test circuit can generate two short-term analog leakage currents, the circuit structure comprises a bridge rectifier BR1, two ac input pins of the bridge rectifier BR1 are connected to a zero line N1 at a power input end of the leakage protector and a live wire L2 at a power output end of the leakage protector, a negative (-) pin of the bridge rectifier BR1 is connected to a common loop point COM (also called a common end, a common connection point) of the whole circuit, a positive (+) pin of the bridge rectifier BR1 is connected to a common end of a first key SW1 (NO type) and a second key SW2 (NO type), the other end of the bridge rectifier SW1 is connected to an anode of a light emitting diode LED1, and the other end of the bridge rectifier SW2 is connected to an anode of the light emitting diode LED 2. The cathode of the LED1 is connected with the common end of the first resistor R1 and the eighth resistor R8. The other end of the first resistor R1 is connected with the drain electrode d of the first field effect tube U1, and the source electrode s of the first field effect tube U1 is connected with the COM end. The other end of the eighth resistor R8 is connected with the cathode of the LED2, and is also connected with the second resistor R2 and the sixth resistor R6. The other end of the second resistor R2 is connected with the third resistor R3 and the capacitor C at the same time, and the other ends of the third resistor R3 and the capacitor C are connected with the COM end. The other end of the second resistor R2 is connected with the cathode of the zener diode D2, the other end of the sixth resistor R6 is connected with the grid electrode g of the first field effect transistor U1, the drain electrode D of the second field effect transistor U2 and the cathode of the first zener diode D1, and the anode of the first zener diode D1, the anode of the second zener diode D2 and the source electrode s of the second field effect transistor U2 are respectively connected with the COM end. The ac input voltage is 220V, resistor r1=6.8kΩ, r2=8mΩ, r3=600kΩ, r6=500kΩ, r8=9.2kΩ, and capacitor c=1 μf. The electrical operation of the schematic diagram of the circuit in block a in fig. 7 is similar to that of embodiment 3, and the description is not repeated here.
As shown in fig. 9, 10, 11 and 12, the circuits in the block in the circuit diagram a use voltage comparators, a single-chip microcomputer MCU, and integrated circuits LM555 and 4016BD chips to generate analog leakage currents with a duration of 0.1 to 0.2 seconds, and also achieve the required electrical performance and operation.
The instantaneous current test circuit of the leakage protector of the embodiment can test whether the leakage protector can trip in time or not by generating an instantaneous short-term and accurate analog leakage current through the electronic element, and can adopt the electronic element with smaller power, so that the reliability of the circuit is improved, the circuit is convenient to miniaturize, and the test is more stable and accurate.
The above embodiments are merely for illustrating the present invention, and are not to be construed as limiting the present invention in any way, and any equivalent embodiments that are part of the present invention or modified by the disclosure of the present invention will be apparent to those of ordinary skill in the art.
Claims (10)
1. The test method is characterized in that the test method adopts a test circuit connected with the input end and the output end of the leakage protector, and the test circuit comprises a rectifying unit, one or two test keys, a current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current; when the test key is pressed, the current unit generates an analog leakage current, and the current value of the analog leakage current is determined by the input voltage of the leakage protector and the current limiting resistance of the current unit; the simulated leakage current is automatically cut off by the cut-off unit after lasting 0.1 to 0.2 seconds;
the rectification unit converts alternating current input by the leakage protector into direct current, and two alternating current input ends of the rectification unit are respectively connected with a power input end and an output end of the leakage protector; the test keys are connected to the direct-current output end of the rectifying unit, and when two test keys exist, the two test keys are in parallel connection; the current unit is provided with a current limiting resistor which is connected with the test key in series;
the input end of the current unit is marked as an N1 end and the input end of the intercepting unit is marked as a K end, and the output end of the current unit is connected with the output end of the intercepting unit to form a common output end which is marked as a COM end;
the current unit comprises a first resistor (R1) and a first triode (Q1), one end of the first resistor (R1) is connected with the N1 end, and the other end of the first resistor is connected with a collector electrode of the first triode (Q1); the intercepting unit comprises a capacitor (C), a voltage stabilizing diode (D3) and a second triode (Q2), wherein one end of the capacitor (C) is marked as an X end and is connected with the K end, and the other end of the capacitor (C) is connected with the COM end; the negative electrode of the voltage stabilizing diode (D3) is connected with the X end of the capacitor (C), and the positive electrode of the voltage stabilizing diode is connected with the base electrode of the second triode (Q2); the collector of the second triode (Q2) is connected with the base of the first triode (Q1) and is connected with the N1 end together, and the emitter electrodes of the second triode (Q2) and the first triode (Q1) are connected with the COM end.
2. The instantaneous current testing circuit of the leakage protector is characterized by comprising a bridge rectifier (BR 1) and a first testing circuit, wherein two alternating current input pins of the bridge rectifier (BR 1) are respectively connected with a power input end and an output end of the leakage protector, one pin is connected with a zero line, and the other pin is connected with a live wire; the first test circuit comprises a first test key (SW 1), a first current unit for generating analog leakage current and a shutoff unit for automatically shutting off the analog leakage current, one end of the first test key (SW 1) is connected with the positive pin of the bridge rectifier (BR 1), and the other end is marked as an M1 end; the input end of the first current unit is marked as an N1 end and the input end of the intercepting unit is marked as a K end, the output end of the first current unit is connected with the output end of the intercepting unit to form a common output end, the common output end is marked as a COM end, the M1 end is connected with the N1 end, and the COM end is connected with the negative pin of the bridge rectifier (BR 1); when a first test key (SW 1) is pressed, the first current unit generates an analog leakage current which is more than or equal to 30mA, and the analog leakage current is automatically cut off by the cut-off unit after lasting 0.1 to 0.2 seconds;
the first current unit comprises a first resistor (R1) and a first triode (Q1), one end of the first resistor (R1) is connected with the N1 end, and the other end of the first resistor is connected with a collector electrode of the first triode (Q1); the intercepting unit comprises a capacitor (C), a voltage stabilizing diode (D3) and a second triode (Q2), wherein one end of the capacitor (C) is marked as an X end and is connected with the K end, and the other end of the capacitor (C) is connected with the COM end; the negative electrode of the voltage stabilizing diode (D3) is connected with the X end of the capacitor (C), and the positive electrode of the voltage stabilizing diode is connected with the base electrode of the second triode (Q2); the collector of the second triode (Q2) is connected with the base of the first triode (Q1) and is connected with the N1 end together, and the emitter electrodes of the second triode (Q2) and the first triode (Q1) are connected with the COM end.
3. The leakage protector instantaneous current testing circuit according to claim 2, wherein a first light emitting diode (LED 1) is connected between the N1 terminal and the first resistor (R1).
4. The leakage protector instantaneous current test circuit according to claim 2, wherein a second resistor (R2) is connected between the K terminal and the X terminal of the capacitor (C), a third resistor (R3) is connected in parallel to the two terminals of the capacitor (C), a fourth resistor (R4) is connected between the X terminal of the capacitor (C) and the negative electrode of the zener diode (D3), a fifth resistor (R5) is connected between the positive electrode of the zener diode (D3) and the COM, a sixth resistor (R6) is connected between the collector of the second triode (Q2) and the K terminal, and a seventh resistor (R7) is connected between the collector of the second triode (Q2) and the base of the first triode.
5. The leakage protector instantaneous current test circuit according to claim 2, further comprising a second test circuit, wherein the second test circuit comprises a second test key (SW 2), a second current unit for generating an analog leakage current, and a shut-off unit for automatically shutting off the analog leakage current, one end of the second test key (SW 2) is connected to the positive leg of the bridge rectifier (BR 1), the other end is denoted as an M2 end, and the shut-off unit of the second test circuit is shared with the shut-off unit of the first test circuit; the input end of the second current unit is connected with the M2 end, the output end of the second current unit is connected with the COM end, and when a second test key (SW 2) is pressed down, the second current unit generates an analog leakage current with rated tripping current of 40-49.9%; the K end of the intercepting unit is connected with the M2 end.
6. The leakage protector instantaneous current testing circuit of claim 5, wherein the second current cell comprises an eighth resistor (R8) and a first transistor (Q1), the eighth resistor (R8) being connected between the K terminal and the input terminal of the first resistor (R1).
7. The leakage protector instantaneous current testing circuit of claim 6, wherein a first light emitting diode (LED 1) is connected between the M1 terminal and the N1 terminal, and a second light emitting diode (LED 2) is connected between the M2 terminal and the K terminal.
8. The leakage protector instantaneous current test circuit according to claim 6, wherein a second resistor (R2) is connected between the K terminal and the X terminal of the capacitor (C), a third resistor (R3) is connected in parallel to the two terminals of the capacitor (C), a fourth resistor (R4) is connected between the X terminal of the capacitor (C) and the negative electrode of the zener diode (D3), a fifth resistor (R5) is connected between the positive electrode of the zener diode (D3) and the COM, a sixth resistor (R6) is connected between the collector of the second triode (Q2) and the K terminal, and a seventh resistor (R7) is connected between the collector of the second triode (Q2) and the base of the first triode.
9. The leakage protector instantaneous current testing circuit according to any one of claims 2, 3, 4, 5, 7, 8, wherein said first transistor (Q1) is replaced with a thyristor.
10. The leakage protector instantaneous current testing circuit according to claim 5, wherein the first triode (Q1) is replaced by a first field effect transistor (U1), one end of the first resistor (R1) is connected to the N1 end, and the other end is connected to the drain of the first field effect transistor (U1);
the second current unit comprises an eighth resistor (R8) and a first field effect transistor (U1), and the eighth resistor (R8) is connected between the K end and the input end of the first resistor (R1);
the capacitor (C), the zener diode (D3) and the second triode (Q2) of the intercepting unit are replaced by the capacitor (C), the first zener diode (D1), the second zener diode (D2) and the second field effect transistor (U2), one end of the capacitor (C) is marked as an X end and connected with the K end, and the other end of the capacitor (C) is connected with the COM end; the grid electrode of the second field effect tube (U2) is connected with the X end of the capacitor (C); the second zener diode (D2) is connected in parallel with the two ends of the capacitor (C), and the negative electrode of the second zener diode (D2) is connected with the X end of the capacitor (C); the first zener diode (D1) is connected in parallel with the two ends of the second field effect tube (U2), and the cathode of the first zener diode (D1) is connected with the drain electrode of the second field effect tube (U2); the grid electrode of the first field effect tube (U1) is connected with the drain electrode of the second field effect tube (U2) and is connected with the K end together; the positive electrode of the first zener diode (D1), the positive electrode of the second zener diode (D2) and the source electrode of the second field effect transistor (U2) are connected with the COM end;
a second resistor (R2) is connected between the K end and the X end of the capacitor (C), a third resistor (R3) is connected in parallel with the two ends of the capacitor (C), and a sixth resistor (R6) is connected between the drain electrode of the second field effect transistor (U2) and the K end.
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