1 / 7

AC Variable Speed

The easiest and cheapest way to control the speed of a process or equipment is to run all equipment at full speed.<br><br>Many applications require the speed of a process or piece of equipment to vary. Before the advent of the adjustable speed drive, many technologies were used, although each had its inherent advantages and disadvantages.

Tabish
Download Presentation

AC Variable Speed

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AC Variable Speed Drive (ASD) - An Overview Variable speed control The easiest and cheapest way to control the speed of a process or equipment is to run all equipment at full speed. Many applications require the speed of a process or piece of equipment to vary. Before the advent of the adjustable speed drive, many technologies were used, although each had its inherent advantages and disadvantages. There are few types of variable speed control: · Control valves, dampers, and vanes · Fossil fuel engines · Eddy current clutches · Hydraulic couplings · Variable pitch sheaves · DC Static Controllers · AD Variable Speed Drives (ASD)

  2. AC variable speed drive (ASD) Variable speed drive (ASD) has become a very popular variable speed control devices used in industrial, commercial, and some residential applications. These devices have been available for about 20 years and have a wide range of applications ranging from single motor pumps, fans, and compressors, to highly sophisticated multi-drive machines. They work by varying the frequency of the alternating voltage supplied to the motor using solid-state electronic devices. These systems are quite expensive but provide more control over the operation and, in many cases, reduce power consumption enough to compensate for the additional cost as little as possible or even exceed it. ASDs allow precise control of the speed of a standard induction motor and can result in significant energy savings and improved process control in many applications. ASD can also control the speed of a standard squirrel cage NEMA Type B induction motor and is suitable not only for new applications but also for upgrading existing motors. Variable Speed Drive (ASD) AC variable speed drives can be thought of as an electrical control device that changes the operating speed of a motor. ASDs can vary the operating speed of the motor by changing the motor's electrical frequency input. The speed at which an AC induction the motor operates is given by the following equation: Synchronous speed = 120 x frequency/number of poles Or: The frequency = the Electric frequency of the power supply in Hz. Number of poles = Number of electric poles in the motor stator.

  3. Change engine speed The speed of the motors can be changed by changing the electric frequency, the number of poles, or both. Motor speed can also be changed by changing the number of poles in a motor from 4 to 2: 4 pole motor operating at 60 hertz = 1800 rpm. 2 pole motor operating at 60 hertz = 3600 rpm. We really changed the speed rather than the varied speed! The motor speed can be changed by changing the frequency of the power supply: 4 pole motor operating at 50 hertz = 1500 rpm. 4 pole motor operating at 40 hertz = 1200 rpm. By varying the frequency, we can adjust the speed over a wide range or vary it with precision using precise changes in the electrical frequency input to the motor. Power and torque ASDs actually control the frequency and voltage, simultaneously maintaining a constant volts/hertz ratio which maintains the current flow similar to full speed conditions. This allows the motor to draw all current at any speed and produce full torque as the motor speed changes. What happens to the power when we reduce speed and torque using frequency? Horsepower = speed (rpm) x torque (pounds sterling) / 5.252 Reduced power = Reduced energy consumption = Energy savings!!

  4. What about the increase in speed? Some motors specially designed for use with ASDs are designed to operate at speeds above normal at frequencies above 60 hertz. Increasing the frequency above 60-hertz speeds up motor operation and creates two main problems: 1. Was the motor or load it drives designed to operate at these higher speeds? Many motors and devices are not mechanically balanced to operate at higher speeds and will create vibration, mechanical, and safety issues. . 2. ASD systems are not able to increase the voltage. So when the frequency exceeds 60 hertz, the torque produced begins to decrease. In order to maintain a constant power to drive our load, if the speed increases, the torque must decrease! At a time of increased speed, we may not be able to produce enough torque to drive the load and at this point, the motor will slow down even with increasing frequency. This point is different for each manufacturer's motor and depends on the torque required by the load. </ P> Only the manufacturer can help determine when this is happening. ASD Advantages and disadvantages Adjustable speed drives have a number of advantages and disadvantages over other types of variable speed drives, including:

  5. Benefits - Energy savings - Improved process control - Reduced voltage starting - Lower system maintenance - Bypass capability - Multi-motor control Disadvantages - Initial cost - Low-speed motor heating - Maintenance - Output harmonics - Induced power line harmonics Variable speed drives can be used to save a significant amount of energy in processing operations compared to traditional control methods in which the load or speed of the operation varies. AC variable speed drives are among the most effective types of speed control when used on axial (variable torque) loads such as centrifugal fans, pumps, and compressors. When the motor reduces the operating speed of the fan, pump, or compressor, the power required to operate the system is greatly reduced. This is one of the main advantages of ASDs and one of the main reasons why ASDs have become so popular in many processing operations. Burraq Engineering Solutions is the best training institute in Lahore which is providing practical training in Electrical Automation and Short Electrical Courses including PLC course, SOLAR SYSTEM Installation, and DESIGN COURSE, ETAPcourse, DIALUX course, Panel FABRICATION course, VFD course, ADVANCED Course The panel, A A SWITCHGEAR design course, Building Electrical design course, and all electrical diploma courses. Both online and physical classes available. We introduce a

  6. platform Lyskills from where you can get lifetime access to your desire courses at a very reasonable price.

More Related