TEAAC IC666 High Voltage Variable Frequency AC Induction Motor

1. Basic concept of variable frequency motor The variable frequency motor adopts the AC speed regulation method of “special variable frequency induction motor + inverter”, which greatly improves the degree of mechanical automation and production efficiency, miniaturizes equipment and increases comfort. It is currently replacing traditional mechanical speed regulation and DC speed regulation schemes.

2. Manufacturing principle of variable frequency motor

1. Electromagnetic design of variable frequency motor For ordinary asynchronous motors, the main performance parameters considered in the design are overload capacity, starting performance, efficiency and power factor. For variable frequency motors, since the critical slip rate is inversely proportional to the power supply frequency, it can be started directly when the critical slip rate is close to 1. Therefore, overload capacity and starting performance no longer need to be considered too much, and the key problem to be solved is how to improve the motor’s adaptability to non-sinusoidal power supply. The methods are generally as follows:

1) Reduce the stator and rotor resistance as much as possible. Reducing the stator resistance can reduce the fundamental wave copper loss to compensate for the increase in copper loss caused by high-order harmonics

2) In order to suppress high-order harmonics in the current, the inductance of the motor needs to be appropriately increased. However, the larger the rotor slot leakage reactance, the greater the skin effect, and the higher harmonic copper loss. Therefore, the size of the motor leakage reactance should take into account the rationality of the impedance matching in the entire speed regulation range.

3) The main magnetic circuit of the variable frequency motor is generally designed to be unsaturated. First, it is considered that high-order harmonics will deepen the magnetic circuit saturation, and second, it is considered that at low frequency, the output voltage of the inverter should be appropriately increased in order to increase the output torque.

2. Variable frequency motor structure design When designing the variable frequency motor structure, the main consideration is the impact of non-sinusoidal power supply characteristics on the insulation structure, vibration, noise cooling method and other aspects of the variable frequency motor. Generally, the following issues should be paid attention to:

1) Insulation level, generally F level or higher, strengthen the insulation to the ground and the insulation strength of the wire turns, and especially consider the ability of the insulation to withstand impulse voltage.

2) For the vibration and noise problems of the motor, the rigidity of the motor components and the whole should be fully considered, and its natural frequency should be increased as much as possible to avoid resonance with each force wave.

3) Cooling method: generally forced ventilation cooling is adopted, that is, the main motor cooling fan is driven by an independent motor.

4) Measures to prevent shaft current: Bearing insulation measures should be adopted for motors with a capacity of more than 160KW. Mainly, it is easy to produce magnetic circuit asymmetry, which will also generate shaft current. When the current generated by other high-frequency components is combined, the shaft current will increase greatly, resulting in bearing damage, so insulation measures are generally required.

5) For constant power variable frequency motors, when the speed exceeds 3000r/min, special high-temperature resistant grease should be used to compensate for the temperature increase of the bearing.