Control of Electric Motors

Current Source Inverter Fed Induction Motor Drive: Current Source Inverter Fed Induction Motor Drive – In a voltage source inverter fed induction motor the applied voltage to the stator is proportional to the frequency, with a correction for the stator resistance drop, particularly at low speeds, to keep the flux constant. It is a very […]

PWM Inverter Fed Induction Motor Drive: Voltage control in the square wave inverter has been external to the inverter, by means of a phase controlled rectifier on the line side. This posed some practical application problems on the drive by limiting the lowest operating frequency and introducing torque pulsations and harmonic heating. However, the harmonic

Square Wave Voltage Source Inverter Fed Induction Motor Drive: Square Wave Voltage Source Inverter Fed Induction Motor Drive is a kind of dc link converter, which is a two stage conversion device. A three phase supply is first rectified using a rectifier on the line side. The rectified dc is inverted to ac of desired

Cycloconverter Feeding Three Phase Induction Motor Drive: Variable frequency supply to an induction motor may be obtained by using a cycloconverter. As has already been discussed, a cycloconverter is a single stage frequency conversion device which converts ac line frequency to a variable frequency. A Cycloconverter Feeding Three Phase Induction Motor Drive is shown in Fig.

Speed Control of Variable Frequency Induction Motor: Speed Control of Variable Frequency Induction Motor of a squirrel cage induction motor can be controlled very effectively by varying the stator frequency. Further, the operation of the motor is eco­nomical and efficient, if it operates at very small slips. The speed of the motor is, therefore, varied

Static Scherbius Drive: The main limitation of the Kraemer drive discussed is the operation at sub-synchronous range due to diode rectifier. Super synchronous speeds can be achieved if the power is fed to the rotor from the ac mains. This can be made possible by replacing the converter cascade by a Static Scherbius Drive system using

Braking and 4 Quadrants Operation: Subsynchronous converter cascades have been used, till now, in applications requiring one quadrant operation. These can be employed for drives where at least one electrical braking is required. A 4 Quadrants Operation can also be made possible in these cascades, using suitable switching. The braking is obtained by connecting the

Speed Control Using Slip Energy Recovery Schemes: The foregoing discussion makes it very clear that the methods of voltage control and rotor resistance control have poor efficiency, particularly at low speeds, and find limited application. The Slip Energy Recovery Schemes is wasted in the rotor resistance, either inherent in the rotor (high resistance rotors for

Chopper Resistance in the Rotor Circuit: Speed control by means of slip variation can be achieved by employing a variable resistance Chopper Resistance in the Rotor Circuit. From the equations it is clear that the maximum value of torque does not depend upon the value of rotor resistance. However, the rotor resistance influences the slip

Derating Factor of an Electric Motor Operating on AC Voltage Controller: Typical derating factor of an induction motor fed from a voltage controller are shown in Fig. 4.5(d) when the motor drives a fan or pump loads (T α N2). The derating factor depends on the rated speed also. Change of phase sequence changes the