What are the working principles and burning faults of fan coil motor?

First, the working principle

At present, single-phase asynchronous motors are widely used in fan coil motors, which have high, medium and low speed regulation, and the speed regulation method is L-shaped speed regulation with sub-phase taps. The number of poles of the motor is four or six poles.

Second, the wiring error caused burning

It is caused by mistaken zero line and parallel use of multiple units.

Burning principle:

When the wiring is wrong, the energized winding is only 3, but the resistance of this winding is very small, which leads to excessive current and sharp temperature rise. Moreover, because the motor thermal protector is connected in series with the zero line, the power supply cannot be cut off, which eventually leads to the motor burning.

Note: When the unit has been running in mid-range, the motor will not burn out.

Distinguish between main and auxiliary:

When the main phase and the auxiliary phase are distinguished, the auxiliary phase lead can be pulled away, and the auxiliary phase winding is connected with it.

Reference case:

1: Many motors in a hotel were burnt down, and the engineering department removed the wiring of the burnt-out units. Another one burned during the inspection on the same day, check the wiring; The yellow line is the zero line, so the high-grade power cord is connected to the zero line of the unit.

2: Many motors in a hotel were burnt down, and it was found on the spot that the power lines all use the same color line. It is found that the power line is confused with the zero line.

The problems are as follows:

1. Multiple units are used in parallel

Two or more coil units are controlled at the beginning of the same control, that is, multiple units are connected in parallel. When the motors are running in high, medium and low grades, there will be potentials on the secondary phase windings, i.e. red, blue and black. Different motors have different potentials on the corresponding color lines. If they are forced to be connected together in parallel, there will be currents flowing from high potential to low potential, which will form a circulating current between the motors, resulting in higher temperature rise of local windings. In severe cases, local windings will burn and the motors will stop running. This burnt-out motor forms a short circuit to the corresponding motor local winding, which will soon lead to the burning-out of another motor local winding. Similar situations will occur for units of the same model due to different wind resistance.

2. Overall high temperature

There are mainly the following factors:

A: abnormal power supply, such as high voltage and unequal frequency;

B: abnormal load, such as the size of air duct and air return box does not meet the requirements, and the wind wheel changes;

C: locked rotation, e.g., wind wheel stuck, etc.

3, turn-to-turn burning

Turn-to-turn short circuit is mainly caused by the damage of paint film.

The factors leading to turn-to-turn short circuit are:

A: there are many pinholes in enameled wire;

B: the paint film is damaged when the stator is wound around the embedded wire;

C: When using, foreign objects poke into the stator, causing damage to the enameled wire.

Third, the inspection process

When the motor does not run, check as follows:

1. Check whether the controller and power supply are normal;

2. Check whether external factors such as air ducts meet the installation requirements;

3. check the motor resistance and unit wiring;

4. Check the stator condition after the motor burns down, and judge according to the above reference.

5. The burning phenomenon is that the vice phase burns black and the main phase is normal, so the unit wiring should be checked. If necessary, the unit wiring of the whole project should be checked.