Introduction
According to incomplete statistics, China's annual the shock accident caused by leakage, fire, caused thousands of deaths and billions of economic losses, and therefore can prevent electric fire and personal electric shock protection performance of leakage protection higher requirements. Automatic test system of the operating characteristics of the article describes the leakage protection measure residual operating current value of leakage protection, breaking time and the current value of leakage does not move, the main technical parameters to improve the reliability of leakage protection, detection process has higher level of automation can be run online and offline running leakage protection testing,Grid tie inverter.
1 system hardware design
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parameters to characterize the leakage protection, which is most closely related to electricity users personal safety relationship residual operating performance, and describe the the residual operating performance of the main parameters for the rated residual operating current (I △ n) and the residual operating time. Rated leakage current leakage protection device under specified conditions specified by the manufacturer must be the action of residual operating current value, which reflects the the leakage leakage protection action sensitivity. Leakage action time means suddenly applied residual operating current from the cut off time until the protection circuit. Malfunction in order to prevent the leakage protection, national standards for the leakage non-operating current (I △ N0), it refers to the leakage protection device must not under the predetermined condition the operation of the leakage current value (priority value 0.5I △ n) is technical parameters of the run must be invested in the electricity grid,power inverter. http://www.gridtieinverter.de/
system has extended test current generation and adjustment module, the the action execution units, the current detection circuit as well as the keyboard and other peripherals,www.12vgridtiepowerinverters.com. LPC2132 is a real-time simulation and tracking 32-bit ARM7TDMI-S core microcontroller, a 10-bit 8-channel A / D converter, two 32-bit timer / counter, 6-channel PWM unit output, two hardware I2C interface and 47 GPIO, 2 16C550 industry standard UART, and up to nine edge or level triggered external interrupt. 16kB on-chip static RAM and 64kB of on-chip Flash program memory to avoid the LPC2132 external expansion memory, simplifying the circuit to improve the operating speed. Leakage protection of the operating characteristics of automated test system block diagram shown in Figure 1.
Figure 1 leakage protection test system block diagram
1.1 test current and adjustment module
test current generating and regulating module shown in Figure 2. The current generation of the test is to output sinusoidal AC 0 ~ 12V, 50Hz, 220V sinusoidal AC 220:12 step-down transformers and electric regulator, and then produce the desired test current through the loop resistance,Grid tie inverter. Test current generation is divided into 3 files, to meet the different measurement ranges. Relay J1 pull, can produce a test current of 0 ~ 1000mA; relay J2 pull, 0 to 500mA test current; relay J1, J2 not pull, can produce 0 ~ 100mA test current. Each stall test current regulation by LPC2132 control electric voltage regulator implementation. In order to make the test current can be changed evenly, the electric voltage regulator using the AC servo control. In the testing process, LPC2132 comparison with the test current value and set value of the collected real-time circuit, and calculates the control amount, the control servo motor rotation, driven electric voltage regulator of the brush to slide stably in the sub edge, the secondary voltage changes, thus changing the current in the loop. LPC2132 P0.2-pin output pulse signal to control the speed of movement of the servo motor, the P0.3 as pin output high or low level signal, and control the direction of rotation of the servo motor.
Figure 2 test current and adjustment module
1.2 current detection circuit
current detecting circuit shown in Figure 3. After sampling the test current through the current transformer on the secondary side of the current transformer output signal after filtering, amplification, the voltage boosting circuit, is converted into a unipolar voltage signal (0 to 5V) can be collected by the A / D module fed into the LPC2132.
detection current size, according to the the test current cycle (frequency) in accordance with 40 points per cycle sampling, sampling a cycle, according to the attenuation of multiples of the current transformer and enhance the value of voltage through software algorithms calculated actual current rms. The circuit should satisfy the following conditions, when the instantaneous value of the AC current reaches a positive peak amplifier output 5V; When the instantaneous value of the AC current reaches the negative peak amplifier output 0V.
3 current detection circuit
1.3 A / D conversion, and control circuit
output signal VOUT
current detecting circuit fed LPC2132 built 8-channel 10-bit high-speed A / D converter input terminal, detects the size of the leakage current,power inverter.
A / D converter 10, when the input voltage is 5V, the output data value is 1024 (4FFH), the maximum resolution for 0.0049V (5V/1024). If you generate test current loop resistance of 12Ω, the resolution of the leakage current 0.4mA (0.0049V/12Ω) fully meet the testing needs. Start signal generated by the leakage current leakage protection and dynamic and static contact disconnect signal were sent to the LPC2132 the external interrupt input, using interrupted action leakage protection, static contact breaking time for testing. P0.5 and P0.6 foot control relay J1, J2 closed and breaking, choose three different measurement range test current. LPC2132 between the host computer using the serial communication system is a 3.3V system SP3232E RS-232 level converter to use. The SP3232E is the 3V power RS-232 converter chip. The A / D converter, and a control circuit is shown in Figure 4.
Figure 4 A / D conversion and a control circuit
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