The function of this high-pressure test stand:
1. The test bench has automatic functions;
2. The test bench can carry out pressure test, continuous pressure rise test and breakdown flashover test of the test product.
3, with a report printing function
4, with SQL database storage
5, with scanning bar code function
The experimental bench consists of: high-voltage test transformer, ball gap protection, intelligent PLC console, low voltage control cabinet, etc.
Test console control principle: Digital ammeter and voltmeter acquisition control system operating parameters on the console. The digital display has MODBUS communication function.
The digital display and PLC communicate in modbus mode, and the computer and PLC communicate via Ethernet.
Problems that occur during the operation:
In the actual operation, in the normal test (no flashover), all instruments communicate properly. When a flashover occurs, the instrument communication chip will be damaged immediately;
problem analysis:
After on-site analysis, the problem occurred on the system ground. When the sample was broken down (flashover occurred), tens of thousands or even tens of thousands of voltages quickly grounded, and the current increased instantaneously, causing the meter measuring port to
The instantaneous voltage increases rapidly, causing the RS485 chip differential signal line level voltage inside the instrument to rise, damaging the chip; under normal circumstances, the differential signal line level voltage is between 7-12V.
Solution:
1. Add optocoupler isolation circuit to the operating voltage pin of RS485 chip.
2, RS485 chip A, B output plus clamping voltage protection, so that the chip's differential signal line level voltage clamped between 7-12v. For example join P6E6.8CA
3. Add resistance and capacitance to the measuring signal of the meter, and add the capacitor and ground the resistor.
4. Replace the RS485 chip with an EE-grade lightning protection chip.
5. Reduce the resistance of the test equipment to earth and control it to 0.5 Euro or less.
result:
After the above transformation, the equipment is in normal use. Even if it breaks down (flashover), the instrument will not be damaged. problem solved. .
Component parameter table
name
model
Quantity
price
capacitance
Operating voltage 275V
Capacity 0.1-0.2uF
6
2 yuan
TVS device
P6KE6.8CA
14
3 yuan
diode
1N4001 or 1N4007
30
0.5 yuan
RS485 lightning protection chip
SP485EE or MAX485EE
6
4-7 yuan
resistance
10-100 ohms
6
1 Yuan
Optocoupler isolation element
TLP521
12
2 yuan