Epekto sa Load sa usa ka Synchronous Motor

Ang synchronous motor nagoperasyon sa konstante nga synchronous speed, walay kalabutan sa load. Karon, atong sulayan ang impakto sa pagbag-o sa load sa motor. Usa ka synchronous motor nga initially nag-run uban leading power factor. Ang phasor diagram nga naka-correspond sa leading power factor gipresentar kini:

Kung ang load sa shaft mag-increase, ang rotor adunay momentary slowdown. Kini mahitabo tungod kay lisud ra ang motor makuha ang additional power gikan sa electrical line. Bisag unsa, bagama't ang rotor nag-maintain sa iyang synchronous rotational speed, efektibong "slips back" sa spatial position tungod sa increased load demand. Sa proseso, ang torque angle δ mag-expand, kini maka-cause sa induced torque nga mag-increase.

Ang equation para sa induced torque gipresentar kini:

Subsequently, ang increased torque nag-accelerate sa rotor, enabling the motor to once again achieve synchronous speed. Pero, kini nga restoration nahitabo uban larger torque angle δ. Ang excitation voltage Ef directly proportional sa ϕω, relying on both the field current and the motor's rotational speed. Given that the motor operates at a constant synchronous speed and the field current remains unchanged, the magnitude of the voltage |Ef| stays constant. Therefore, we can conclude that

Gikan sa equations above, it becomes evident that when the power P increases, the values of Ef sinδ and Ia cosϕ also rise accordingly.The following figure illustrates the impact of a load increase on the operation of a synchronous motor.

As depicted in the figure above, as the load increases, the quantity jIaXs steadily grows, and the equation V=Ef+jIaXs 

remains valid. Concurrently, the armature current also rises. The power factor angle undergoes a transformation with the load variation; it gradually becomes less leading and then increasingly lagging, as clearly illustrated in the figure.

In summary, when the load on a synchronous motor increases, the following key observations can be made:

• The motor maintains its operation at the synchronous speed.

• The torque angle δ expands.

• The excitation voltage Ef stays constant.

• The armature current Ia drawn from the power supply increases.

• The phase angle ϕ shifts further in the lagging direction.

It's important to note that there is a limit to the mechanical load that a synchronous motor can handle. As the load continues to rise, the torque angle δ keeps increasing until a critical point is reached. At this juncture, the rotor is pulled out of synchronism, causing the motor to come to a halt.

The pull - out torque is defined as the maximum torque that a synchronous motor can generate at the rated voltage and frequency while still maintaining synchronism. Typically, its values range from 1.5 to 3.5 times the full - load torque.