A variable-frequency drive with synchronous bypass and transfer capabilities can help reduce long-term energy and maintenance costs in various motor-control applications.
By Brad Bugiardini, product manager, Medium Voltage Drives, and Gary Bankay, MV commercial engineer support, Rockwell Automation
The savings keep coming when you use a variable frequency drive (VFD) with synchronous bypass and transfer capabilities. It can help reduce up-front capital costs and long-term energy and maintenance costs in various motor-control applications. The VFD also can help increase efficiency and achieve more flexible process control.
A VFD with synchronous capabilities allows you to operate one motor continuously with variable speed control or to start and synchronize multiple motors. It also gives you the ability to soft start large motors. Let’s take a closer look at each of these abilities.
Operating One Motor
When operating one motor, the VFD operates the motor continuously with variable speed control and can transfer the motor to the bypass source when necessary.
This application can increase overall system efficiency to achieve energy savings. It also can deliver more savings by removing, or not requiring, the use or maintenance of certain apparatuses.
In fan applications, for example, dampers can be removed or left open, because they’re no longer needed to obtain variable airflow. In pumps, valves can be left open, because they’re no longer required to provide flow control.
Operating Multiple Motors
With synchronous capabilities, one VFD can start and synchronize multiple motors. This can reduce your full load current and energy consumption and optimize your process.
The number of motors that can be operated is limited by external factors, such as bus capacity and cabling limitations. But in some instances, the synchronous transfer application has been successfully applied to a 10-motor system.
There are two possible options in a multi-motor application: 1) all motors can be of equal rating, and 2) a range of motor horsepower can exist. In the second scenario, the drive system must be sized for the largest motor’s horsepower, but also be able to control the smallest motor.
A soft-start application is used to start motors, accelerate to full speed and transfer to the bypass source.
The drive isn’t intended for continuous application. Therefore, the drive’s ampacity rating can be reduced to match the starting requirement for the load. The drive is not rated for the motor horsepower rating, only the starting horsepower requirement.
Find the Right Drive
So, take the time to see if the drive is right for your operations. It could put you in the good graces of everyone from technicians on the plant floor, who have fewer parts to maintain, to the CFO, who’s looking to rein in energy costs in production.
Learn about VFDs with synchronous bypass and transfer capabilities from Rockwell Automation.
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