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PORTABLE GENERATORS

Smaller ­ Better - Quieter

Field Day, Emergency Operations, Camping, Power Failures ­ they all create the need for reliable, portable power. This presentation will look at a number of available generators in the 1000-6500W range that share a desirable characteristic ­ they use an inverter to produce clean, AC power.

We will look at the evolution of generator design and how an inverter generator functions. Also, we will look at how to safely use a generator.

Portable generators (gensets) have evolved over the last 10-15 years to be the quiet, light and fuel efficient devices available today. They are capable of producing AC power that is virtually a pure sine wave and that maintains the necessary 60 Hz line frequency at a reliable 120 Volts. Even with these improvements, these devices are available at prices that are about the same as those available 10 years ago. So, let's talk about what a "generator" really is.

How Simple Can A Genset Be?

Gasoline/Diesel Engine Permanent Magnet Alternator

THE CHALLENGES OF A CREATING A "PRACTICAL" GENSET

Weight Noise Cooling Fuel Consumption Power Regulation (Both Voltage and Frequency)

ALL of these requirements interact to a great extent!

Obviously, the lighter a Genset can be, the easier it is to handle. Lighter materials can be part of a design. Convenient carrying handles are also a help. The choice of engine can greatly influence the design process. Two Cycle engines, while having a higher power output per pound, need to run at higher RPMs, are inherently noisier, subject to wear in use, need specifically prepared fuel and tend to use more fuel. Diesel engines are long-lived, have better fuel economy but are often significantly noisier and heavier. Four cycle, air cooled, gasoline engines tend to be the choice for most current designs.

REGULATION

In a conventional generator, frequency is regulated by varying the RPM of the engine. This is accomplished by a mechanical or vacuum operated governor controlling the throttle. To produce a 60 Hz output, the engine typically rotates the generator at 3600 RPM When load increases, the engine speed slows and the governor responds by opening the throttle. This response is not instantaneous so the system depends on a flywheel and the rotating mass of the generator to bridge that gap. When the load decreases, the opposite occurs. Some more advanced generator designs incorporate an electronic Automatic Voltage Regulator (AVR) which can respond much more quickly than a governor. These are typically found in home backup generator systems.

WHY IS REGULATION IMPORTANT?

Standard Gensets, when not under load, can output voltages as high as 160V and frequencies as high as 64 Hz! When under full load conditions, the voltage can drop to as low as 105V and the frequency to 56 Hz! Modern electronics (Radios, Computers, TVs, etc.) are subject to stress of components or outright failure when exposed to these extremes of voltage and frequency. Additionally, some of the less expensive or "contractor grade" Gensets produce power that is more of a square wave than a sine wave. Electronics do not thrive well at all on this diet.

INVERTERS

But, there is a better way to get clean, well regulated power ­ an INVERTER! An AC-DC-AC inverter, working with an engine governor, is what we will examine more closely. The alternators in these systems use up to 24 poles to produce AC output at up to 20 Khz. This high frequency AC is used, similar to a switching power supply, to produce DC. At this point, we have a small bonus ­ some generators tap this DC to provide an output for battery charging. We can now send the DC power to an inverter to produce Clean, regulated AC power, as needed, without significant variations in voltage and frequency as loads change.

POWER RATINGS

Most Gensets have two power ratings: surge and continuous. Surge is what it can deliver for a short period of time (2 -3 seconds) to supply additional power needed to start up some devices. Continuous is what it can deliver for extended periods of time. Power ratings for your generator have to match or exceed the total requirements of the devices to be powered including their surge requirements.

Typical Power Requirements

DEVICE Incandescent/Halogen Lights Computer & Monitor Coffee Maker Microwave Small Refrigerator/Freezer Box Fan Space Heater Small TV 100W HF Transceiver 600W Solid State Linear Amplifier WATTAGE 20 - 500 Up to 800 Up to 1,000 Up to 1200 600* 200 Up to 1,500 300 Up to 500 Up to 1200

* These devices may require more than double the power to start up

RUN TIMES

Run Times for Gensets are expressed in a variety of ways: Full Load or Partial Load. Full Load reflects operation at the continuous rating while Partial Load run times are expressed in a fractional part of the continuous rating (i.e. 8.6 Hours at 1/4 Load). A few Gensets allow operation with auxiliary tanks to extend operation times.

GENERATOR SAFETY

READ THE MANUAL!! ALWAYS operate your generator outdoors!! Shield the generator from rain and liquids as necessary. Exhausts are HOT!!! Keep extension cords and electrical outlets out of puddles!!! Disconnect all loads before starting your generator, your electronics will thank you for this!

Electrical grounding of a Genset is mired in some level of controversy. Some users feel the the system is safest when left floating while others insist on a grounding rod(s). If there is any question about proper grounding, always defer to the manufacturers recommendations or any applicable electrical codes. ALL electrical cords should have three prong plugs and three wires! If your generator does not have Ground Fault Current Interrupter (GFCI) outlets, consider using an external device.

Size electrical cords according to the loads presented by the devices being powered. Low wattage loads, for distances of up to 100 feet, may be adequately carried 14 -16 AWG cords. For high wattage loads, 12 AWG is called for. Inspect all cords before use for damaged insulation or exposed wires and loose connectors.

FIRE SAFETY

NEVER refuel a generator without allowing at least five minutes to cool down

Always have a properly charged, ABC rated, fire extinguisher on hand and placed between you and the generator

Always store fuel in safety cans and away from the generator or open flames

Learn the proper technique for operating your fire extinguisher

COMPARISON OF SELECTED INVERTER GENERATORS

Output (W) Surge/ Cont 1000/900 2100/2000 4300/3800 2400/2000 2000/1600 2000/1600 6500/5500 RunTime (H) Full/ Partial Load NA/(1/4) 12.0 NA/(1/2) 5.0 5.3/NA NA/(1/4) 8.6 4.0/(1/4) 9.6 NA/(1/4) 6.5 4.7/(1/4) 14.0 Noise Level (dBa) 47 - 57 dBA 65 dBa 62 dBa 53 ­ 58 dBa 53 ­ 59 dBa N/A 60 ­ 52 dBa Dry Weight (Lbs) 28 59 163 75 46 50 254+ DC Output (A) 8 8 8 8 8 5 N/A Price (MSRP) $879 $899 $2,799 $1.332 $1,150 $649 $3,695

Make/Model Yamaha/ EF 1000 IS Honeywell/ Hw2000i Cummins Onan/ P4300ie Yahama/ EF2400iSHC Honda/ EU2000i Briggs & Stratton/ P2000 Honda/ EU6500ISA

Engine Type OHV, Air-Cooled, FourStroke, Single Cylinder OHV, Air-Cooled, FourStroke, Single Cylinder OHC, Air-Cooled, FourStroke, Single Cylinder OHV, Air-Cooled, FourStroke, Single Cylinder OHC, Air-Cooled, FourStroke, Single Cylinder OHV, Air-Cooled, FourStroke, Single Cylinder OHV, Air-Cooled, FourStroke, Single Cylinder

SUMMARY

Modern Inverter Generators are small, light, quiet, fuel efficient and kind to your valuable electronics ­ What's not to like??

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