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Since rotation at synchronous speed does not induce rotor current, an induction motor always operates slightly slower than synchronous speed. The difference, or "slip," between actual and synchronous speed varies from about 0.5% to 5.0% for standard Design B torque curve induction motors. [30]
The machine thus starts as an induction motor until it approaches synchronous speed, when the rotor "pulls in" and locks to the stator field. [19] Reluctance motor designs have ratings that range from fractional horsepower (a few watts) to about 22 kW. Small reluctance motors have low torque, and are generally used for instrumentation ...
An induction generator produces electrical power when its rotor is turned faster than the synchronous speed. For a four-pole motor (two pairs of poles on stator) powered by a 60 Hz source, the synchronous speed is 1800 rotations per minute (rpm) and 1500 RPM powered at 50 Hz. The motor always turns slightly slower than the synchronous speed.
The rating of a brushless motor is the ratio of the motor's unloaded rotational speed (measured in RPM) to the peak (not RMS) voltage on the wires connected to the coils (the back EMF). For example, an unloaded motor of K v {\displaystyle K_{\text{v}}} = 5,700 rpm/V supplied with 11.1 V will run at a nominal speed of 63,270 rpm (= 5,700 rpm/V ...
During this period the rotor moves at synchronous speed ω s in rad/s. The electric torque T e corresponds to the net air-gap power in the machine and thus accounts for the total output power of the generator plus I 2 R losses in the armature winding. The angular position θ is measured with a stationary reference frame.
In vector control, an AC induction or synchronous motor is controlled under all operating conditions like a separately excited DC motor. [21] That is, the AC motor behaves like a DC motor in which the field flux linkage and armature flux linkage created by the respective field and armature (or torque component) currents are orthogonally aligned such that, when torque is controlled, the field ...
A synchronous motor may have a squirrel-cage winding embedded in its rotor, used to increase the motor starting torque and so decrease the time to accelerate to synchronous speed. The squirrel cage winding of a synchronous machine will generally be smaller than for an induction machine of similar rating.
Synchronous reference frame: Reference frame speed is equal to synchronous speed(ω= ω e), variables denoted by f e dqo or f d e, f q e and f os, transformation matrix denoted by K s e. The choice of reference frame is not restricted but otherwise deeply influenced by the type of analysis that is to be performed so as to expedite the solution ...