Induction Motor

SUMMARY (Induction Motor)

3.6 Most induction motors in industrial and household use operate in an uncontrolled manner, being supplied directly from the power system. The motor speed is roughly constant, but the developed torque is sensitive to changes in the stator voltage. In many applications, significant energy savings could be realized by replacing the uncontrolled drive with an […]

ABNORMAL OPERATING CONDITIONS (Induction Motor)

3.5 Abnormal operation of an induction motor drive may be caused by internal or external problems. The most common electrical and mechanical faults in the motor are: FIGURE 3.6 Pole changing: (a) four-pole stator winding, (b) eight-pole stator winding. 1. Short circuit in the stator winding, which can occur between turns of the same phase […]

CONTROL OF STATOR VOLTAGE (Induction Motor)

4.1 As seen from Eq. (3.3), the speed of an induction motor can be controlled by changing the number of poles, slip, and the supply frequency. The pole changing has already been described, and, if the motor has that capability, it only requires an appropriate switch. Changes of slip can be effected by varying the […]

POWER ELECTRONIC CONVERTERS FOR INDUCTION MOTOR DRIVES

In this topic, we review power electronic converters used in ASDs with induction motors. Various types of rectifiers providing the dc supply voltage for inverters feeding the motors are presented, and we describe voltage source inverters, including three-level and soft-switching inverters, and current source inverters. Control methods for inverters, with a stress on the use […]

RECTIFIERS (Induction Motor)

4.2 Rectifiers in induction motor ASDs supply dc voltage to inverters. The three-phase full-wave (six-pulse) diode rectifier, shown in Figure 4.1, is most commonly employed. At any time, only two out of six diodes conduct the output current, iQ. These are the diodes, subjected to the highest line-to-line input voltage. For instance, if at a […]

INVERTERS (Induction Motor)

4.3 The three-phase voltage source inverter (VSI) is shown in Figure 4.13. The voltage source for the inverter is made up from a rectifier and the so-called dc link, composed of a capacitor, C, and inductor, L. If the ac machine fed from the inverter operates as a motor (i.e., in the first or third […]

FREQUENCY CHANGERS (Induction Motor)

4.4 A cascade of a rectifier, dc link, and inverter can be thought of as a frequency changer, in which the fixed-frequency input voltage and current are converted into adjustable-frequency output variables. Frequency changers with a reversible power flow are of particular interest in the drive technology. The rectifier in such a scheme may be […]

CONTROL OF VOLTAGE SOURCE INVERTERS (Induction Motor)

4.5 To explain the principles of control of inverters, it is convenient to introduce the so-called switching variables, variously defined depending on the type of inverter. For the most common, two-level voltage source inverter depicted in Figure 4.13, three binary switching variables, a, b, and c, one per phase of the inverter, are sufficient. As […]

CONTROL OF CURRENT SOURCE INVERTERS (Induction Motor)

4.6 Current source inverters are less commonly used in induction motor ASDs than voltage source inverters, mostly due to the poorer quality of output currents. Still, they have certain advantages, such as imperviousness to overcurrents, even with a short circuit in the inverter or the load. The absence of freewheeling diodes further increases the reliability. […]

SUMMARY (Induction Motor)

4.8 Induction motors in ASDs are supplied from inverters, which are dc to ac power electronic converters. The dc supply voltage for inverters is provided by rectifiers. These usually have the three-phase bridge topology and are based on power diodes or, if control of the input current or inverted power flow is required, on SCRs. […]

← Previous Entries

Next Entries →