A simple method to determine the AC and DC power supply
The AC and DC power supplies in the power box and terminal box inside the substation were not clearly labeled during construction. Due to the age of the rescue table, it is difficult to see clearly. If electrical equipment is blindly connected, accidents may occur. We have experienced multiple incidents of mistakenly connecting welding machines and voltage regulators to DC power sources, resulting in equipment burnout accidents. Based on work experience, there are few simple methods for judging AC and DC power supplies, for beginners to refer to.
1. Use a measuring pen to determine if only one pole of the neon tube inside the measuring pen emits light, then the measured power source is direct current, and the principle is that when one pole of the metal head of the measuring pen (i.e. the pole close to hand touch) is lit, the measured power source is positive, otherwise it is negative.
2. Use a mechanical multimeter to determine and test the multimeter in both AC and DC voltage ranges. If there is a reading in the AC gear and no reading in the DC gear, then the measured power source is AC power; If the readings measured in two gears are similar, then the measured power supply is DC.
3. Use a digital multimeter to determine and test the multimeter in both AC and DC voltage ranges. If there is no reading in the DC gear while reading in the AC gear, then the measured power source is AC power; On the contrary, it is direct current. If the DC power is impure, there will also be readings when using an AC DC TV, but the values are generally very small, which is actually the AC component contained in the DC power.
Basic knowledge of DC power supply
A DC power supply has two electrodes, positive and negative, with the positive electrode having a high potential and the negative electrode having a low potential; When two electrodes are connected to the circuit, the DC power supply can maintain a constant potential difference between the two electrodes, thereby forming a constant current from positive to negative in the external circuit.
There are two important physical quantities that characterize the characteristics of a power supply: one is the electromotive force E of the communication power supply, and the other is the internal resistance (referred to as internal resistance) r0 of the switching power supply.
To maintain a constant potential difference between the two poles of the power supply, it is necessary to ensure that the positive charge flowing from the positive pole to the negative pole in the external circuit returns to the positive pole inside the power supply against the direction of the electric field force. This process cannot rely on electrostatic forces, but can only be achieved by some 'non electrostatic force' that is opposite in direction to the electrostatic force. Therefore, a power source is a device that provides non electrostatic force, which works by converting non electric energy into potential energy between positive and negative electrodes.
There are many types of DC power sources, and different types of DC power sources have different properties of non electrostatic forces and different processes of energy conversion.
