#POSSIBL VALUES OF SYNCHRONOUS SPEED NS SERIES#

That is, one coil corresponds to an N-pole, the other to an S-pole until the phase of AC changes polarity.

#POSSIBL VALUES OF SYNCHRONOUS SPEED NS SERIES#

The individual coils of a pair are connected in series and correspond to the opposite poles of an electromagnet. The 2-phase induction motor stator above has 2-pairs of coils, one pair for each of the two phases of AC. The stator in the figure above is wound with pairs of coils corresponding to the phases of electrical energy available. Figure 5.3 Tesla polyphase induction motor The simple 2-phase induction motor below is similar to the 1/2 horsepower motor which Nikola Tesla introduced in 1888. By induction motor, we mean that the stator windings induce a current flow in the rotor conductors, like a transformer, unlike a brushed DC commutator motor.ДЄn induction motor is composed of a rotor, known as an armature, and a stator containing windings connected to a polyphase energy source as shown in the figure below. While we include numerous illustrations of two-phase motors for simplicity, we must emphasize that nearly all polyphase motors are three-phase. In practice, this is two or three phases. By polyphase, we mean that the stator contains multiple distinct windings per motor pole, driven by corresponding time-shifted sine waves. Tesla sold the manufacturing rights to George Westinghouse for $65,000.Most large ( > 1 hp or 1 kW) industrial motors are polyphase induction motors. Nikola Tesla conceived the basic principles of the polyphase induction motor in 1883 and had a half horsepower (400 watts) model by 1888. In fact, 90% of industrial motors are induction motors. Induction motors are favored due to their ruggedness and simplicity. AC motors also have some losses not encountered by DC motors: hysteresis and eddy currents. Thus, one goal is to maximize motor efficiency, reducing heat loss. It must be removed from the motor and may adversely affect longevity. The heat is an undesired byproduct of this conversion. Some of the electric energy is lost to heat, another form of energy, due to I2R losses (also called copper losses) in the motor windings. Unfortunately, electric motors are not 100% efficient. Such has been the case with diesel-electric locomotives on a smaller scale for many years.ДЄt the system level, (Figure above) a motor takes in electrical energy in terms of a potential difference and a current flow, converting it to mechanical work. The figure above shows the family tree of the AC motors described in this chapter.Д¬ruise ships and other large vessels replace reduction geared driveshafts with large multi-megawatt generators and motors. And, the stepper motor, a digital version of the motor, is driven by alternating current square waves, again, generated by solid-state circuitry. The brushless DC motor, actually an AC motor, is replacing the conventional brushed DC motor in many applications. Modern solid-state electronic circuits drive brushless DC motorsВ withВ AC waveformsВ generated from a DC source. Above one horsepower (750 W), the Tesla motor reigns supreme. Yet small brushed AC motors, similar to the DC variety, persist in small appliances along with small Tesla induction motors.

Its ruggedness and simplicity make for long life, high reliability, and low maintenance. His new type of motor, the AC induction motor, is the workhorse of the industry to this day. Nikola Tesla envisioned an entirely new type of motor when he visualized a spinning turbine, not spun by water or steam, but by a rotatingВ magnetic field. Steinmetz contributed to solving these problems with his investigation of hysteresis losses in iron armatures. Figure 5.1 AC electric motor family diagramД¬harles P. Initially, AC motors were constructed like DC motors, but numerous problems were encountered due to changing magnetic fields. However, motors were a problem with alternating current. Transmission of electrical energy covered longer distances at a lower loss withВ alternating current. The lighting worked as well on AC as on DC. Motors that rotate slower than the synchronous speed are called asynchronous motors.After the introduction of the DC electrical distribution system by Edison in the United States, a gradual transition to the more economical AC system commenced.

Synchronous speed No = ДЇ = Frequency p = Number of magnetic polesДЄ collective name for the motors that run at the synchronous speed is the synchronous motor. It is determined by the frequency and the number of magnetic poles. Synchronous speed is a significant parameter for the rotating magnetic field-type AC motor.

Possibl values of synchronous speed ns