Category: DC Motor Drives

Closed Loop Speed Control of DC Motor

Closed Loop Speed Control of DC Motor: Closed Loop Speed Control of DC Motor – The converters (rectifiers and choppers) are built using semiconductor devices, which have very low thermal capacity. Consequently their transient and steady state current ratings are same. The dc motors can carry 2 to 3.5 times the rated current during transient […]

Chopper Control of Series Motor

Chopper Control of Series Motor: Motoring : Chopper Control of Series Motor and va and ia waveforms will be same as shown in Fig. 5.41. Va is given by Eq. (5.113). However, e is not constant but varies with ia. Due to saturation of magnetic circuit, relationship between e and ia is non-linear. The approximation is already […]

Chopper Control of Separately Excited DC Motor

Chopper Control of Separately Excited DC Motor: Motoring Control : A transistor Chopper Control of Separately Excited DC Motor drive is shown in Fig. 5.41(a). Transistor Tr is operated periodically with period T and remains on for a duration ton. Present day choppers operate at a frequency which is high enough to ensure continuous conduction. […]

Drawbacks of Rectifier Fed DC Drives

Drawbacks of Rectifier Fed DC Drives: Drawbacks of Rectifier Fed DC Drives are as follows: 1. Distortion of Supply: Source current of a rectifier has harmonics. In a weak ac source, with high internal impedance, current harmonics distort source voltage. Furthermore, temporary short circuit of lines during commutation of thyristors, causes sharp current pulses, which […]

Rectifier Control of DC Series Motor

Rectifier Control of DC Series Motor: Single-phase controlled Rectifier Control of DC Series Motor are employed in traction. A single-phase half-controlled Rectifier Control of DC Series Motor is shown in Fig. 5.37(a). Equivalent circuit of motor is also shown. Since back emf decreases with armature current, discontinuous conduction occurs only in a narrow range of […]

Four Quadrant Drive With Field Reversal

Four Quadrant Drive With Field Reversal: Four Quadrant Drive With Field Reversal as shown in Fig. 5.36, armature is fed from a fully-controlled rectifier and the field from a dual converter so that field current can be reversed. With field current in one direction, the motor operates is quadrants I and IV. When field current […]

Dual Converter Control of DC Separately Excited Motor

Dual Converter Control of DC Separately Excited Motor: A Dual Converter Control of DC Separately Excited Motor (Fig. 5.35) consists of two fully-controlled rectifiers connected in anti-parallel across the armature. For power ratings upto around 10 kW, sigle-phase fully-controlled rectifiers can be used. For higher ratings, three-phase fully controlled rectifiers are employed. Rectifier A, which […]

DC Motor Reversing Switch Diagram

DC Motor Reversing Switch Diagram: DC Motor Reversing Switch Diagram is shown in Fig. 5.34(a). A fully-controlled rectifier feeds the motor through a reversing switch RS which is used to reverse the armature connection with respect to the rectifier. A fully-controlled rectifier is capable of providing operation in quadrants I and IV. The reversal of […]

Three phase Fully Controlled Rectifier Control

Three phase Fully Controlled Rectifier Control of DC Separately Excited Motor: Three phase Fully Controlled Rectifier Control (6 pulse) fed separately excited dc motor drive is shown in Fig. 5.32(a). Thyristors are fired in the sequence of their numbers with a phase difference of 60° by gate pulses of 120°duration. Each thyristor conducts for 120, […]

Single Phase Half Controlled Rectifier Control

Single Phase Half Controlled Rectifier Control of DC Separately Excited Motor: Single Phase Half Controlled Rectifier Control is shown in Fig. 5.29(a). In a cycle of source voltage defined by Eq. (5.71), T1 receives gate pulse from α to π and T2 from (π+ α) to 2π. Motor terminal voltage and current waveforms for the dominant […]