Variable Frequency Drive Applications - Australiaprice: contact company for price
controlled by a damper at the inlet of the fan scroll or in some cases
by a variable pitch drive sheave. For most of these applications a
variable frequency drive is much more efficient and retrofit is very
cost-effective. For buildings that have a centrally controlled HVAC
system, one variable frequency drive can be installed to achieve
maximum kW savings.
The role of variable frequency drive cable is to provide the most attractive path for these potentially harmful currents to return to the VFD with minimal disturbance to the surrounding networks and instrumentation. A VFD cable that provides the lowest impedance ground path will be most effective in reducing VFD common mode currents. It is observation that systems with a significant number of smaller VFDs tend to be proportionally more likely to see issues with common mode noise. We attribute this tendancy to faster switching devices and reduction of VFD output filtering in the more cost sensitive VFD products.
A VFD can often provide smoother operation compared to an alternative fixed speed mode of operation. For example, in a sewage lift station, sewage usually flows through sewer pipes under the force of gravity to a wet well location. From there it is pumped up to a treatment process. When fixed speed pumps are used, the pumps are set to start when the level of the liquid in the wet well reaches some high point and stop when the level has been reduced to a low point. Cycling the pumps on and off results in frequent high surges of electric current to start the motors resulting in electromagnetic and thermal stresses in the motors and power control equipment, the pumps and pipes are subjected to mechanical and hydraulic stresses, and the sewage treatment process is forced to accommodate surges in the flow of sewage through the process. When VFDs are used, the pumps operate continuously at a speed that increases as the wet well level increases. This matches the outflow to the average inflow and provides a much smoother operation of the process.
- Posted By: AC Variable Frequency Drives
- Phone: 61291130618
- Address: Wattle Street Asquith NSW 2077, NSW, Australia
- Website: http://www.vfds.org/
Published date: December 23, 2013 -
- Business Description: A VFD (see http://www.vfds.org ) is a system for controlling the
rotational speed of an AC electric motor by controlling the frequency of
the electrical power supplied to the motor. A VFD is a specific type of
variable frequency drive.
VFDs are also known as adjustable frequency drives (AFD), variable speed drives (VSD), AC drives or inverter drives. Since the voltage is varied along with frequency, these are sometimes also called VVVF (variable voltage variable frequency) drives.
VFD is widely used in ventilation systems for large buildings; variable speed motors on fans save energy by allowing the volume of air moved to match the system demand. They are also used on pumps, elevator, conveyor and machine tool VFDs.
VFD installations can increase energy efficiency (in some cases energy savings can exceed 50%), improve power factor and process precision, and provide other performance benefits such as soft starting and over speed capability. They also can eliminate the need for expensive and energy wasting throttling mechanisms such as control valves and outlet dampers.
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