Use a test pen to touch the live wire and neutral wire respectively:
①The neutral wire will not respond and the light will not turn on because the neutral wire is directly connected to the earth. ;
② When the test pen contacts the live wire, the light will turn on, because the live wire itself is live. When the test pen contacts the live wire, current flows. through the test pen through the human body then to the earth.
How to use a test pen to identify live wire and neutral wire:
1. First of all, the equipment to be prepared for testing is: two resistors (one of which is half-watt and 680K), an electric pen, plastic copper core hard wires, a single-pole double-pole switch and a plug power cord.
2. Precautions for using the test pen:
(1) When using the test pen, be sure to alwaysdear the metal part at the end of the test pen with your hand, otherwise, the charged body and the test pen may The electric pen, the human body and the earth do not form a circuit, and the neon bulb in the test pen will not emit light, causing error in judgment and thinking that the charged object is not charged, which is very dangerous.
(2) Before using the test pen, first check whether there is a safety resistance in the test pen, then visually check whether the test pen is damaged, s It is affected by moisture or water, and it can only be used after passing inspection.
A test pen is also called a test pen, or “electric pen” for short. This is an electrician's tool used to test whether electrical wires are live. There is a neon bulb in the pen body. If the neon bulb glows during the test, it means the wire is electrical or it isacts as a live wire in the path. The tip and tail of the test pen are made of metal materials, and the pen body is made of insulating materials.
When using the test pen, be sure to touch the metal part at the end of the test pen with your hand, otherwise, because there is no circuit between the charged body, the test pen and the human body. and the ground, the neon bulb in the test pen will not emit light, causing error in judgment, thinking that the charged object is not charged.
Detailed information:
In addition to being able to determine whether an object is charged, the test pen also has the following uses:
(1) It can be used to perform low-voltage tests Checking the voltage phase and measuring all wires in the circuit whether they are in phase or out of phase. The specific methode is as follows: Stand on an object isolated from ground, hold a test pen in each hand, and then test the two wires to be tested. If both test pens glow very brightly, the two leads are otherwise in phase; , it's the same phase.
It is based on the principle that the voltage difference between the two poles of the neon bulb in the test pen is proportional to the intensity of its luminescence.
(2) Can be used to distinguish between alternating current and direct current. When testing with an electric test pen, if both poles of the neon bulb of the test pen light up, it is alternating current; if only one of the two poles emits light, it is a direct current;
(3) You can determine the positive and negative poles of direct current. Connect the test pen to the DC circuit for testing. The illuminated pole of the neon bulb is the negative pole and the unlit pole is the positive pole.
(4)Sayavailable to determine if DC is grounded. In a DC system isolated from the ground, you can stand on the ground and touch the positive or negative pole of the DC system with a test pen. If the test pen neon bulb does not light up, there is no ground. phenomenon.
If the neon bulb shines, it means that there is a grounding phenomenon. If it glows like the tip of the pen, it means the positive electrode is grounded. If it lights up on your fingertip, it means the negative pole is grounded. It should be noted, however, that in a DC system with a ground monitoring relay, this method cannot be used to determine if the DC system is grounded.
The voltage test pen is one of the tools frequently used by electricians to determine whether an object is charged. Its internal structure is a bulb with two electrodes. The bulb is filled with gas bornon, commonly known as neon bulb. One pole is connected to the pen tip and the other pole is connected in series with high resistance. then connected to the other end of the pen. When the voltage between the two poles of the neon bulb reaches a certain value, a glow occurs between the two poles and the intensity of the glow is proportional to the voltage between the two poles.
When the voltage of the grounded charged object is higher than the initial glow voltage of the neon bulb and the tip of the test pen touches it, the other end is switched to the earth through the human body, so that the test pen will glow. The function of the resistance of the electric test pen is to limit the current flowing in the human body to avoid danger.
References:
The situation you mentioned will need toit be due to movement of neutral point after single phase earthing in three phase power system and the earthed phase becomes opposite. The ground voltage is zero and the neutral point lead wire (neutral line) should be grounded, but it has been disconnected from ground, so the neutral line voltage rises to the phase voltage (220V), which is equivalent to the neutral line and the functions of the grounded phase wire are reversed, that is, the neutral wire becomes the live wire and the live wire becomes the live wire neutral. I think the motor you mentioned should be a single phase motor, because if it is a 3 phase motor it will not start due to phase loss. Even if the phase is missing during operation, it will generate significant heat, the load. the capacity will decrease and the ammeter reading will be too high, etc. , if it is a single-phase motor, it is locatedve that it is connected to the grounded single-phase phase line and the neutral line. The voltage between the two lines is. always 220v, so the motor can start normally and charge without being affected. The same principle applies to electric lamps. They should also be taken from this grounded phase wire, except that the original neutral wire becomes the live wire and the live wire becomes the neutral wire. The voltage is also 220 V, so not only. won't explode, but it will light up normally. If the phase wire taken by the above equipment is not the grounded one but another phase wire, it will be troublesome, because the rated voltage of the single-phase motor itself is 220 V. After the grounded, original wiring of a zero and a light. becomes two. If the live wire, i.e. the voltage applied to the winding, changes from the phase voltage of 220 V to the line voltage of 380 V, the motor windingr may grill. If the lamp is also applied with a voltage of 380 V, the brightness should increase instantly, then the filament will burn out quickly due to overvoltage. If the transformer ground wire is energized, it must be the transformer ground wire. The ground condition is not good, there is a large resistance to the ground, or it has simply been disconnected, and there is also a three-phase imbalance.