While our customers are wholesalers, Packard knows that you, the contractor, have a choice. You are often presented with many buying options, and being well-informed about your purchase can help make your job easier and more successful. Our Tech Tips are also very helpful for our wholesalers as we present product information that can help as contractors have questions.
This is why we have dedicated a section of our site for contractors and wholesalers. In this section, you will find helpful product tips, tools and some clips from our training classes. We’ve also provided a distributor locator so you can find the nearest wholesaler who can give you access to Packard products.
How does an ECM save energy when compared to a PSC?
The electronically commutated motor (ECM) is a permanent magnet motor while the permanent split capacitor (PSC) is an induction motor. To operate either motor, power is applied. The amount of power applied is measured in Watts. This is often referred to as “Watts In”. This power is then converted to work. This work, or output power, is usually referred to as horsepower. However, horsepower can be converted to Watts. One horsepower equals 746 Watts. The output work can be measured as “Watts Out”. The Watts Out divided by the Watts In is the efficiency of the motor. A 6-pole (1075 RPM) PSC motor is 60% efficient on high speed. On medium speed it is about 50% efficient, and about 40% efficient on low speed. The ECM is 80% efficient at all speeds. The higher efficiency of the ECM will result in more work from the motor for an equivalent amount of power supplied to the motor as compared to the PSC. This will be seen in lower electric bills.
This is only part of the picture. Another important aspect of the ECM is that it can be operated at a much lower speed than a PSC.
When operating a load, power is consumed. The fan laws tell us that power consumed is to the cube of the speed. If a load were operated at twice the speed, it would require 8 times the amount of power (the cube of 2, the change of speed, is 2 x 2 x 2 = 8). If the speed was reduced by 1/2, then the required power to operate that same load would be reduced by 1/8 (the cube of 1/2, the change of speed, is 1/2 x 1/2 x 1/2 = 1/8)
In order to keep the math easy, assume that I operate a blower at 1650 RPM. To achieve 1650 RPM, 8 horsepower, or 5,968 Watts is required. If I were to operate the very same load at 1/2 of the speed, that is 825 RPM, it would now require only 1 horsepower, or 746 Watts. That represents a savings of 5,222 Watts! These same principles apply to pumps, and other devices. This is why variable frequency drives (VFDs) have become so popular. By reducing the frequency to the motor the speed can be reduced, resulting in significant energy savings.
By operating an ECM on continuous fan at a much lower speed than what a PSC can be operated, significant energy can be saved. Plus, the blower will operate more quietly, continuously filtering the air and eliminating stratification of air, that is, hot spots and cold spots in the living area.
Not only is the efficiency of an ECM much higher than a PSC, but the ability to operate the ECM at a much lower speed will result in significantly less power consumption.
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