This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. Its general construction is shown in Fig. 1. It is usually designed for fixed-speed operation, larger ratings having such features as deep rotor bars to limit Direct on Line (DOL) starting currents. Electronic variable speed drive technology is …
Motor starting problem and high motor inrush currents
Electric motor protection device depends on the accurate and correct selection of overload(s), fuses and/or circuit breakers. Over the years the protective devices have been selected according to the applicable code requirements with only minimal nuisance tripping. However, in recent years, the problem of nuisance tripping due to the high motor inrush currents that occur …
What is the major difference between a two-phase and a three-phase stator?
Rotor Behavior In a Rotating field For purposes of explaining rotor movement, let’s assume that we can place a bar magnet in the center of the stator diagrams of figure 0. We’ll mount this magnet so that it is free to rotate in this area. Let’s also assume that the bar magnet is aligned so …
5 steps to choose best motor for your application
Step 1: Know the load characteristics For line-operated motors, loads fall into three general categories: constant torque, torque that changes abruptly, and torque that change gradually over time. Bulk material conveyors, extruders, positive displacement pumps, and compressors without air unloaders run at relatively steady levels of torque. Sizing a motor for these applications is simple …
Why do we need variable speed drives (VSD)?
Reasons for using variable speed drives There are many and diverse reasons for using variable speed drives. Some applications, such as paper making machines, cannot run without them while others, such as centrifugal pumps, can benefit from energy savings. In general, variable speed drives are used to: • Latch the speed of a drive to …
Motors and drives for efficient control – ABB
Potential for major energy savings With electric motors accounting for an estimated 65 percent of industrial energy use, any increases in efficiency clearly provide the potential for major savings. The energy consumption of electric motors can be reduced in two main ways – by implementing efficient speed control and by increasing the efficiency of the …
DC motor and generator – design, application and operation
DC Motor History will recognize the vital role played by DC motors in the development of industrial power transmission systems, the dc machine being the first practical device to convert electrical power into mechanical power. Inherently straight forward operating characteristics, flexible performance and high efficiency have encouraged the widespread use of DC motors in many …
Cooling and ventilation of electric motors (IC)
All rotating electrical machines generate heat as a result of the electrical and mechanical losses inside the machine. Losses are high during starting or dynamic braking. Also, losses usually increase with increased loading. Cooling is necessary to continuously transfer the heat to a cooling medium, such as the air. The different methods of cooling rotating …
AC motors – Protection against short circuits
Every electric motor has operating limits. Overshooting these limits will eventually destroy it and the systems it drives, the immediate effect being operating shutdown and losses. A short circuit is a direct contact between two points of different electric potential: – Alternating current: phase-to-phase contact, phase-to-neutral contact, phase-to-ground contact or contact between windings in a …
Construction of 3-Phase AC induction motors
For industrial and mining applications, 3-phase AC induction motors are the prime movers for the vast majority of machines. These motors can be operated either directly from the mains or from adjustable variable frequency drives. In modern industrialized countries, more than half the total electrical energy used in those countries is converted to mechanical energy …
