Electrical Machines

What is PWM Inverter?: What is PWM Inverter? – In presenting the arguments here attention will be focused on a single-phase inverter. Instead of the single rectangular pulse output of Figs 11.46 and 11.48 during each half-cycle, a commutation circuitry can be devised to produce a series of short duration pulses as output in each […]

Voltage and Harmonic Control of Inverters: Voltage and Harmonic Control of Inverters – In applying Inverters for motor control both V and f (keeping V/f constant) need to be varied. Further, the inverters apply essentially nonsinusoidal ac voltage to the motor. External filter circuits cannot be employed due to the difficulty in operating inverters over

Three Phase Bridge Inverter | Working Principle: The basic three phase bridge inverter is a six-step inverter. A step is defined as a change in the firing sequence. A 3-phase thyristor bridge-inverter is shown in Fig. 11.49. Th1 to Th6 are the six load-carrying thyristors while D1 to D6 are the free-wheeling diodes. Each pair

Single Phase Bridge Inverter: A serious disadvantage of the half-Bridge Inverter of Fig. 11.46 is that it requires a 3-wire dc supply. This is overcome by the commonly employed Single Phase Bridge Inverter circuit of Fig. 11.48(a) which needs four thyristors and four free-wheeling diodes. The sequence of thyristor gating and the output waveforms are shown

Single Phase Half Bridge Inverter | R Load | RL Load | RLC Load: Figure 11.46(a) gives the circuit configuration of a Single Phase Half Bridge Inverter. It has two thyristors and two free-wheeling diodes. Each thyristor is gated at frequency f = 1/T of the ac supply desired. The gating signals of the two

Phase Control of Three Phase Induction Motor: Figure 11.44 shows the schematic representation of Phase Control of Three Phase Induction Motor. Two thyristors are connected in antiparallel in each line. The firing sequence of the thyristors for all modes of operation is 1, 3′, 2, 1′, 3 and 2′ as shown in Fig. 11.45. The

Static Kramer Drive: The Static Kramer drive system which consists of variable-speed drive system shown in Fig. 11.43 consists of a slipring induction motor and a rectifier-fed dc motor. The machines are connected electrically in cascade. The slip power recovery takes place through the rectifier and the auxiliary dc motor. Torque supplied to the load

Static Scherbius Drive Circuit Diagram: A basic scheme of a Static Scherbius Drive Circuit Diagram converter cascade, that is employed for recovery of slip power in electrical form itself, is given in Fig. 11.42. For achieving both subsynchronous and supersynchronous speed control, converters C1 and C2 must be fully-controlled thyristor bridges, one functioning at slip

Induction Motor Speed Control Methods: The only way to control the speed of a synchronous motor is to control the input frequency and voltage such as to keep V/f constant. The Induction Motor Speed Control, on the other hand, can be controlled by the following means: Stator Voltage Control Frequency Control Slip Control 1. Stator

Basic Principle of Chopper Circuit: A Basic Principle of Chopper Circuit is essentially a thyristor switch in series with the load as shown in Fig. 11.27(a). A shunting diode is provided across the load for free-wheeling the load current when the thyristor is off. The thyristor shown enclosed by a dotted square can be turned-on