It is easy to argue numbers but difficult to make sense of all of it. This is particularly true if the presenter is arguing “apples with oranges”. The Caterpillar and Cummings White Paper Reports argue in favor of AC generators, but the example(s) used in the comparison of DC generator technology leave Polar’s technology out of the picture. There are many types of AC and DC alternators; the Caterpillar and Cummings White Papers implied that all DC generators use the same technology and have the same efficiency. This is not the case.
Polar coined the term DC alternator for a brush-less Permanent Magnet Alternator; our electrical output is a high frequency (400 to 800 Hz), low voltage output optimized for conversion into DC without using a switch mode power supply as illustrated by Caterpillar and Cummings. The high frequency AC current passes through a simple diode bridge circuit then connects to and charges the battery directly, requiring no other electronics.
In Telecom, the term rectifier refers to a battery charger/power supply. In other Engineering Fields, a rectifier refers to a diode. This is where some confusion arises, the Polar DC generator uses a simple diode bridge and few other DC generator systems use a switch mode circuit to regulate voltage and current.
The best fuel efficiency test data is from field trials, not laboratory testing. Typically, laboratory testing fails at simulating real world use of generators as used in their applications. There are too many variables to account for in simulating the real world and at the same time laboratory engineers are always trying to simplify testing parameters. Also, it is unreasonable to compare two manufacturers’ equipment performance by using product data sheets. For an accurate comparison, both tests should use the same test technicians, fuels, weather conditions, loads, test equipment, and operate in actual field conditions.
The purpose of this report is to visually examine the differences in Polar’s technology versus Caterpillar’s Cummings’ and Generac’s technology. For those with some mechanical and electrical backgrounds, common sense will prove the point.
For high energy efficiency electric motors and alternators, most engineers target their design efficiency to be within 90 and 96%. Designers of electromagnetic machinery and power supplies very rarely include the parasitic losses, and marketing never mention them.