In today’s world of power transmission overloads in the.doc

In today’s world of power transmission overloads in the Northeast, blackouts in the West, the Department of Energy (DOE) is concentrating their efforts on reducing energy consumption. Approximately 63% of industrial electrical power consumed in the U.S. is used to operate electric motors according to the DOE. Water pumping is one of those applications that uses electric motors. Every municipality deals with getting water to and from every home and business. As these communities go throughout their day, the water usage varies. When the demand decreases, control valves are adjusted, yet the motor stays running full speed. This could be similar to approaching a red traffic light and instead of reducing the engine speed, you simply apply the brake on your car. Most people would say that’s an inefficient way to operate your car and it is! There is a better method of reducing the flow and/or pressure when the demand doesn’t call for it. That method is using an Adjustable Speed Drive (ASD). This technology is also known by the terms: Variable Frequency Drive (VFD), Variable Voltage/ Variable Frequency (VVVF), Variable Speed Drive (VSD) or just plain Inverters. In this article, we will refer to them as Adjustable Speed Drives (ASDs), because that is what they truly are, “adjustable”. ASDs adjust the speed of AC induction type motors from zero speed to 3 or 4 times their normal across-the-line speed or base speed by changing the voltage and frequency supplied to the motor. This adjustment can come from several different sources, such as the operator or by intelligence built into control. Which adjustment source used is entirely based upon the initial set up of the control. *Adjustable Speed Let’s look at an example to see how adjusting speed can benefit an application. In this application if a 100Hp pump is required. First, there are 3 facts about variable torque type pumps (Also known as the affinity laws), which we should keep in mind: The flow produced is