condition

condition

condition

The torque of an asynchronous motor is proportional to the square of the voltage

condition

condition

λm overload multiple =Tm/TN

Starting torque ratio λ=Tst1/Tst2

z2s=r2≈sN*E2N/√2I2n

Reverse braking

feedback braking

Energy consumption braking

Cage asynchronous motor

subtopic

The number of pole pairs of the cage rotor can automatically follow the change of the number of pole pairs of the stator.

By changing the current direction of one of the half-phase windings, the number of pairs of magnetic poles produced by the motor can be changed.

Y-YY transformation

Δ-YY transformation

The equipment is simple, has relatively hard mechanical properties, and operates reliably. High efficiency, suitable for constant torque speed regulation. It can also be applied to approximately constant power speed regulation.

Only step-by-step speed adjustment is possible

Constant torque load

Fan load

Applicable to

Changing the size of the thyristor trigger delay angle α can change the size of the motor stator voltage, thereby achieving speed regulation.

Modern voltage and speed regulation system

The equipment is simple, the initial investment is low, and it is suitable for production machinery that does not require high speed regulation.

At low speed, the copper loss of the rotor is large, the efficiency is low, the motor heats up seriously, the mechanical properties are soft, and the stability is poor.

Extreme speed regulation

E2 is the induced electromotive force when the rotor is open circuit, which is a constant. When changing the size of the additional electromotive force Ead, The size of the slip ratio s can be changed to achieve the purpose of speed regulation.

The rotor electromotive force sE2 is rectified into DC, and then added to the On the thyristor inverter, the inverter converts DC into AC , connected to the grid through a transformer

Hard mechanical properties, good speed regulation smoothness, It can achieve stepless speed regulation and high efficiency. But the equipment is complicated and the cost is high

High-voltage, large-capacity situations such as driving fan equipment

Super synchronous cascade speed regulation

Subsynchronous cascade speed regulation

U1≈E1=4.44f1N1kw1Fm

Approximate constant power speed regulation

principle

advantage

The frequency is continuously adjustable, enabling stepless speed regulation with a wide speed regulation range. It has hard mechanical properties, good rotational speed stability and high efficiency.