What are DC Drives and How it Works?

What are  DC Drives?


1.0   Introduction


DC drives are defined as Electric drives using DC motors as prime movers. DC motor drives were dominated variable speed applications before the introduction of Power Electronic converters. But they are still popular even after the invention of power electronics. Common applications are rolling mills, hoists, traction, and cranes.

•         Controlled rectifiers provide a variable dc output voltage from a fixed ac voltage, whereas a dc-dc converter can provide a variable dc voltage from a fixed dc voltage.
•         Due to their ability to supply a continuously variable dc voltage, controlled rectifiers and dc-dc converters made a revolution in modern industrial control equipment and variable-speed drives, with power levels ranging from fractional horsepower to several megawatts.
•         Controlled rectifiers are generally used for the speed control of dc motors.
•         The alternative form would be a diode rectifier followed by dc-dc converter.
•         DC drives can be classified, in general, into three types:
–       1. Single-phase drives
–       2. Three-phase drives
–       3. DC-DC converter drives

Advantages of DC motor:

  • ·        Precise torque and speed control without sophisticated electronics
  • ·        Deliver high starting torque
  • ·       Near-linear performance


Disadvantages:

  • ·        High maintenance
  • ·        Large and expensive (compared to induction motor)
  • ·        Not suitable for high-speed operation due to commutators and brushes
  • ·        Not suitable in explosive or very clean environment
  •      Commonly used DC motors

—  Separately excited
—  Series (mostly for traction applications)

Comments

Post a Comment

Popular posts from this blog

Basic Concepts of Instrumentation and Controls for Oil & Gas Sector

Image
In part one of this instrumentation and control (I & C) series, we'll go over the fundamental terminology and concepts used when working with industrial plants. This is the first of a series of technical articles about instrumentation and control. In this series, we will discuss the basic concepts and principles that govern the operation of industrial plants. Concepts associated with measurements of flow, level, temperature and pressure, electronics and pneumatics instrumentation, control loops, PID control, and others will be addressed. Article Scope Someone once asked a colleague what his occupation was. He replied without hesitation, "I am an instrumentation and control engineer." "And what is that?" asked his interlocutor. "...Oh. Oh ... I'm in trouble," thought the engineer. To explain what a mechanical, electrical, chemical, or electrical engineer does is relatively easy, but it is another story to concisely describe the work pe
Read more

What is Ics, Icm

Icu:  The rated breaking capacity (Icu) or (Icn) is the maximum fault-current a circuit-breaker can successfully interrupt without being damaged. The probability of such a current occurring is extremely low, and in normal circumstances the fault-currents are considerably less than the rated breaking capacity (Icu) of the CB. On the other hand it is important that high currents (of low probability) be interrupted under good conditions, so that the CB is immediately available for reclosure, after the faulty circuit has been repaired. It is for these reasons that a new characteristic (Ics) has been created, expressed as a percentage of Icu, viz: 25, 50, 75, 100% for industrial circuit-breakers.
Read more

What is Hydrograph, Topograph, Hectograph, Monograph?

Image
Hydrograph:  A hydrograph is a plot of the variation of discharge with respect to time (it can also be the variation of stage or other water property with respect to time). Discharge is the volume of water flowing past a location per unit time (usually in cubic feet per second (cfs)). Topograph:  Topography  is the study of the shape and features of the  surface  of the  Earth  and other     observable  astronomical objects  including  planets ,  moons , and  asteroids .The topography of an area could refer to the surface shapes and features themselves, or a description (especially their  depiction  in maps). Hectograph:  The hectograph was an early duplicating method. "Hecto" means one hundred, so this is a method designed to make (roughly) a hundred copies of something. With the advent of cheap computer printers, there's not a lot of practical use for this technology. But it's a fun method of duplicating, and produces surprisingly good copies. With this
Read more