What is a VSD?
A Variable Speed Drive (VSD) is a device that is used to change the electrical supply to a motor to reduce the speed. VSDs offer a high degree of motor control, accurately varying motor speed according to demand whilst adjusting torque accordingly - all within the specifications of a particular manufacturer.
There are different types of VSD's and different sizes ranging from 0.2kW to in the order of several Mega Watt's. It is important to match the correct size and type of VSD to the application. A VSD will also need to be programmed to suit the application. Programming will vary according to the manufacturer and the specific installation however options may include the time taken to 'ramp up' the drive, the required speed settings and how the VSD is controlled.
VSDs can have a wide range of applications however some of the more common are:
Feeders and augers
How A VSD Can Save Energy Costs?
During the operation of an electric motor the requirement for its operational loading may vary. For instance a water pump may only be required to run at 100% capacity during peak times. When operating outside of this peak time perhaps the motor can be reduced to 70% of its capacity thus reducing its energy usage. Often fans, pumps and drive speeds can be reduced with little to no impact on the application.
The reduction in energy usage associated with the reduction in speed is not linear and this is where savings can be recognised. Reducing a motors speed by 20% can in some cases reduce energy usage by up to 50% making the installation of a VSD a very attractive option.
VSD's also provide a soft start reducing initial current draw on startup. This may also provide savings for motors that are starting and stopping frequently.
Other Advantages of a VSD
VSDs have numerous benefits that go beyond energy efficiency, they can:
Reduced stress on system components such as motors and bearings by allowing soft starting, which can extend equipment life
Allow precise control over applications such as conveyors and process equipment
Assist to improve workplace safety and amenity, through reduced heat and noise levels
VSD's can be integrated with existing PLC and BMS systems to provide seamless automation/control
Is a VSD right for You?
To accurately determine if a VSD may reduce your energy costs it is important to understand the existing operating conditions of your motors. You will need to determine the load duty cycle, or percentage of time that motor operates at each load point. Once determined this information can be compared to the know operating efficiencies of the recommended VSD to provide the expected energy and cost savings.
Another determining factor will be the life expectancy of the application. The installation cost of a VSD varies greatly depending on the specific site requirements. However this capital expenditure can generally be offset by the energy savings in the long term.
Saving energy makes sense on every level and VSD's are a great energy saving option for industrial applications.
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References and Reading Material