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 …

Read More »## Three Phase Induction Motor Performance

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 …

Read More »## Torque Speed Characteristics of Induction Motor

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 …

Read More »## Three-Phase Induction Motor Efficiency

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 …

Read More »## Three 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 …

Read More »## Three Phase Induction Motor Working Principle

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 …

Read More »## Three Phase Induction Motor Construction

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 …

Read More »## Electric Motor Nameplate Details Explained | Induction Motor Nameplate

Figure 1 is a drawing of a typical induction motor nameplate. The electric motor nameplate contains a variety of information that can be used to calculate other items. NEMA specifies the information that must be included on the motor’s nameplate. The motor manufacturer may include additional information, such as the …

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