How is the three phase resistance imbalance of the motor caused?

1. The motor is damp, overloaded and overheated for a long time, resulting in inter-turn short circuit due to winding insulation damage, which will make the DC resistance of the three-phase winding unbalanced.

2. The motor is seriously damp, seriously overloaded, and out of phase due to rain, resulting in damage to the winding insulation, short circuit, grounding or open circuit, which will make the resistance of the three-phase winding unbalanced.

3. Caused by the three-phase load imbalance and the asymmetry of the three-phase parameters of the system components. Three-phase imbalance.

This will result in additional heating of the rotating machine.

and vibration, increased magnetic flux leakage and local overheating of transformers, increased line loss of the power grid, and malfunction of various protection and automatic devices, etc.

The reason for the unbalanced three-phase resistance of the motor is the reduction of insulation and the short circuit between turns.

Electric machinery (commonly known as "motor") refers to an electromagnetic device that converts or transmits electrical energy according to the law of electromagnetic induction. In the circuit it is indicated by the letter M (D in the old standard).

Its main function is to generate driving torque, as a power source for electrical appliances or various machinery. Generators are denoted by the letter G in the circuit. Its main role is to use mechanical energy to convert into electrical energy, and the most commonly used at present is to use thermal energy, water energy, etc. to push the generator rotor to generate electricity.

The most basic reason is the reduction of insulation and the short circuit between turns.

If there is a short circuit in the winding, it is equivalent to a decrease in the number of coils, and the resistance is smaller.

Phase-to-phase short circuits, turn-to-turn short circuits, manufacturing defects.

Will the number of coil turns be deliberately reduced during maintenance?

The motor is three sets of independent coils, if the three groups of coils are disconnected, the measured resistance is 0, it is a short circuit between the three sets of coils, and the motor cannot be used. If the three sets of coils are not disconnected, that is, the resistance between the three terminals of the motor is directly measured, it is equal to 0, which does not mean that the motor is damaged, because the coil resistance of the motor with slightly larger power is very small, and the ordinary meter measures that the resistance of 0 is completely normal. It is necessary to use a milliohmmeter to measure its resistance value.

Summary. How is the three-phase resistance imbalance of the motor caused? Hello dear , glad for your question :

The three-phase resistance imbalance of the motor is mostly caused by the inter-turn short circuit in the winding? Under normal circumstances, the three-phase resistance value of the three-phase motor is equal, if a phase winding coil has an inter-turn short circuit, the resistance value will be smaller than the resistance value of the other two-phase winding coils, and the unbalanced resistance of the three-phase winding of the three-phase asynchronous motor will cause the motor to burn out.

How is the three-phase resistance imbalance of the motor caused? Hello dear, glad to have your question: The three-phase resistance imbalance of the motor is mostly caused by the inter-turn short circuit in the winding?

Under normal circumstances, the three-phase resistance value of the three-phase motor is equal, if a phase winding coil has an inter-turn short circuit, the resistance value will be smaller than the resistance value of the other two-phase winding coils, and the unbalanced resistance of the three-phase winding of the three-phase asynchronous motor will cause the motor to burn out.

Okay, thanks.

The resistance value of the V phase is greater than that of the other two phases.

Among them, the resistance value of the V phase is larger than that of the other two phases, and I am glad to ask you for your question: the interphase resistance value of the motor includes the DC resistance value of the winding and the interphase insulation resistance value. The DC resistance value of the winding is measured by the U, V and W binding posts respectively after the winding is connected, and the resistance value of the three measurements is equal to indicate that there is no inter-turn short circuit.

To measure the insulation resistance value between phases, the connection group of the motor should be disassembled, and the resistance value between the binding posts of U, V and W should be measured with a 500V shake meter, and the above is qualified.

There is no break between turns, alas, what's going on.

There is no open circuit between turns, alas, what's going on Hello dear, I'm glad for your question: short circuit refers to a very small resistance and a very large current. One of the cases of non-short circuit is that the resistance is large enough and the current is small enough, and the other is that when the coil passes through the alternating current, the coil will generate an induced electromotive force in the opposite direction to the alternating voltage, and when the inductance is large enough, the inductive reactance reduces the alternating current voltage and current, so that there will be no short circuit.

Coils mostly fall into the latter category.

( ) The three-phase current imbalance will lead to the increase of the loss of the motor and the aggravation of heating, so this situation should be avoided, and the three-phase current unbalance should first check whether the three-phase power supply voltage is balanced, and find out the cause of the three-phase current imbalance of the motor.

The main reasons for the three-phase current imbalance are: 1. If the one-phase voltage drop of the line is too large for some reason, resulting in the three-phase voltage imbalance, the three-phase current is also unbalanced, and if the power supply is out of phase and the motor is out of phase, the current in the other two-phase windings rises sharply, which is the most serious situation of the three-phase current imbalance.

2. There is an open circuit fault in a certain branch of the motor winding, resulting in different three-phase impedance, so the three-phase current is unbalanced.

3. If the interphase, turn or ground short-circuit fault occurs in the three-phase winding of the motor, if the short-circuit fault is serious, the fuse will be fused, and if the short-circuit fault is not serious, the fuse will not fuse, and the three-phase current will be unbalanced.

4. After repairing the motor (after rewinding the motor winding), due to the wrong phase head and phase tail, the first phase is reversed or some coils in the winding are reversed, which will also make the three-phase current unbalanced.

5. Improper operation and maintenance. The operator can not do a good job of inspection and maintenance of electrical equipment on a regular basis, which is artificially caused by the lack of power and phase of the motor, resulting in unbalanced current.

There are the following reasons for the unbalanced three-phase current of the motor in operation:

1. Route reasons.

Poor contact or fuse of the test line fuse wire; Three-phase unbalance of power supply voltage; The three test wires are not properly connected to the motor terminals.

2. The reason for the motor wiring.

Internal wiring errors, including one or several coils in a polar phase group, inverted or incorrect head and tail connections, reverse polar phase combinations, incorrect connection of multiple parallel winding branches, etc.;

3. The motor winding is wrong.

There is a short circuit or open circuit fault in the winding; The polarity of the power line (start and termination) is mismarked; Poor welding;

4. The number of winding turns is wrong.

The number of turns of the three-phase winding is not equal after the winding is rewound.

5. The launcher is wrong.

The starter is in poor contact, which makes the motor coil partially broken.