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Induction Motor

Reduced Voltage Motor Starters

reduced voltage starter

Induction motors draw very large currents when started at full voltage. Thus, it is desirable, especially for large motors, to start them at reduced voltage to keep the starting current low. Reduced voltage motor starting methods include resistance starting, reactance starting, autotransformer starting, wye-delta starting, part-winding starting, and electronic soft …

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Single-Phase Induction Motor Working

single phase induction motor

Figure 1 shows the cross-sectional view of a single-phase induction motor. Consider the motor in Figure 1 at standstill. Current is applied to the windings, establishing two counter-rotating waves. As they sweep past the rotor bars they both try to start the machine but they cancel each other out. Thus, …

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Starting Methods of Three Phase Induction Motor

Results of Y-Delta motor start

Three-phase Induction motors draw six or more times rated current when started at rated voltage. Such high currents may pose serious problems for the motor and the electrical system when large motors are started. One way to reduce the starting current is to start the motor at reduced voltage. After …

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Three Phase Induction Motor Performance

Characteristic curves of an induction motor

Using the equivalent circuit of the three-phase induction motor and some additional information about the mechanical and core loses, one could calculate the performance of the three-phase induction motor from no-load to full-load. Figure 1 shows a set of generic curves of efficiency, current, power factor, and slip for an …

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Torque Speed Characteristics of Induction Motor

Induction motor torque-speed characteristic 2

Figure 1 showed a plot of induction motor torque vs speed from zero to synchronous speed. This curve is called the torque-speed characteristic curve. We can derive an equation from the equivalent circuit that allows the calculation of the torque for a given value of slip. FIGURE 1    Induction motor …

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Three-Phase Induction Motor Efficiency

Power flow diagram for an induction motor

The equivalent circuit of the induction motor can be used to examine the losses and the efficiency of the machine. Efficiency is defined for an induction motor the same way as it is for any device: \[\begin{matrix}   \eta =\frac{Power\text{ }Out}{Power\text{ }In}=\frac{{{P}_{out}}}{{{P}_{in}}} & {} & \left( 1 \right)  \\\end{matrix}\] Defining the …

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Three Phase Induction Motor Equivalent Circuit

Per-phase induction motor equivalent circuit

The three-phase induction motor operates in some ways like a transformer. In the transformer, AC voltage is applied to the primary, which creates AC flux in the core. That flux links the secondary and induces a voltage of the same frequency, but with a voltage that depends on the transformer …

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Three Phase Induction Motor Working Principle

difference between dc motor and dc generator

The three-phase induction motor, like all electric motors, operates by means of interaction between magnetic fields. The stator magnetic field in a three-phase induction motor rotates around the air gap between the stator and the rotor. The direction of field rotation determines which way the motor turns and is controlled …

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Three Phase Induction Motor Construction

Exploded view of a three-phase induction motor

Like all motors, a three-phase induction motor contains a stator (the stationary part) and a rotor (which rotates). Each contains electrical windings that carry current and thus creates a magnetic field. The interaction of the magnetic fields creates the torque that rotates the rotor and the load. Figure 1 shows …

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