Working Principle of Microcomputer Relay Protection Tester
The relay protection test instrument is divided into two circuits: the main circuit and the auxiliary circuit. The main circuit is adjusted by a large knob, while the auxiliary circuit is adjusted by a small knob. The main circuit controls its various output quantities through the "output selection" button switch on the panel, and each time the output is switched, the digital voltage/current meter on the instrument can automatically monitor the output value. The auxiliary circuit directly adjusts the output through the output switch control, and the measurement can be performed with an external multimeter.
Main Circuit Principle of Relay Protection Test Instrument
The input AC220V power supply passes through the fuse and enters the input end of the double carbon brush voltage regulator T1 through the output control relay K1. The electric quantity adjusted by the large knob of T1 enters the isolation transformer T2 (also serving as a current booster). The current booster has three tap outputs: one tap outputs AC0-250V with a rated current of 3A; the output voltage of this tap can be rectified and filtered to output 0-350V DC voltage; the second tap is 15V (10A), which outputs 0-10A AC current through a sensor and relay control, 0-500mA AC current through a resistor, and can be converted by a relay to output 0-10A or 0-500mA DC current; the third tap is the 10V (100A) high current terminal, which passes through the primary side of the sensor and directly outputs 100A current. This circuit has strong load capacity, but if the output is slightly overloaded, it cannot be in a high current state for a long time. Thermal relay calibrator
Auxiliary Circuit of Relay Protection Test Instrument
The auxiliary circuit of the relay protection test instrument is the same as the main circuit. The AC220V power supply enters the double carbon brush voltage regulator T1 through the fuse, and the voltage adjusted by the small knob can be directly adjusted to output 0-20V or 0-250V AC voltage or 0-350V DC voltage through the isolation transformer T4. The rated current of this circuit is 1A. Press the "output control" switch of the auxiliary circuit and adjust the small knob to output.
