Power Inverters

As consumers and service facilitators continue to turn to independent energy sources, primarily wind and sun, to power everything from homes and RVs to entire communities, parks, plus medical and military structures, energy inverters, or adaptors play an important role in the performance, efficiency and safety of independent energy systems and devices.

Ranging in size and application from simple solar yard lighting to portable and emergency backup systems, energy systems that are not connected to the utility grid share one common factor: a storage battery which collects and releases energy as DC or direct current electricity.

By contrast, municipal electric utility grids run on AC or alternating current, that is, anything that plugs directly into an electrical outlet in your home or business. For practical reasons, alternating energy works better for long distances. Because DC electricity can’t readily be directly utilized in our mobile focused lifestyles, inverters are essential to convert DC into AC electricity.

Inverters are complicated

Even though most power adapters or inverters appear to be just boxes with switches, there’s a lot going on inside those unassuming little boxes. For instance, a simple home solar inverter is called on to manage a broad range of loads, a.k.a. devices, from a simple light bulb to a well pump to a vacuum cleaner or power tool.

Oh, and your inverter regulates the output quality all of the devices it manages within a narrow window of constraint, with minimal power loss. So it stands to reason that choosing the appropriate inverter is no walk in the RV Park either, due to a laundry list of considerations:

  • What devices or loads do you need the inverter to manage?
  • What inverter options are available?
  • What type of environment is the inverter for?
  • Does the inverter conform to electrical standards?

Electricity— You’ve got some explaining to do

Wattage:  Watts simply measure the amount of power a device uses or can supply. A watt is a watt is a watt – some confusion exists in the usage of the terms, "watts per hour" and "watts per day". For example, a laptop computer that uses 100 watts could use 5 volts (amount of pressure) x 20 amps (rate of electricity).

Whether the device draws 5 amps at 20 volts or 1 amp at 100 volts, it is still 100 watts. Because one watt = one Joule per second, the term, “watts per hour," is the electrical equivalent of, “miles per hour per day."

Kilowatt hours:  A kilowatt-hour or kWh, what people mean by, “watts per day,” measures the amount of watts times the length of time in hours that electricity is used for that device per use. A 60-watt light bulb left on for 10 hours, uses 600 watt-hours. Likewise, an air compressor, running at 2000 watts for 20 minutes uses 400 watt-hours. A space heater, at 1000 watts x 4 hours = 4000 watt hours.

Amp-hours: When someone talks about AH or amp-hours they generally are referring to amps per hour or amps multiplied by time—Amps x time = AH. Amp-hours are of interest, because most inverters run from batteries and because amp-hours measure a battery’s capacity, the AH capacity denotes how long your device will run. 

How much wattage do you need?

Choose an inverter that is sized for the maximum peak load and for the typical continuous load of your device.

Surge power refers to the maximum power an inverter can supply. Appliances with electric motors, pumps and air compressors need a lot more power to start than they do when they are running continuously.

Typical power refers to the power an inverter needs to supply on continuing basis, which is the continuous rating.

Average power is lower than both surge and typical power ratings and is only useful in estimating battery capacities.

High speed vs. transformer

The most common inverters, high-speed electronic switching mechanisms, are used for lowest surge ratings, typically with 25%-50% maximum overload capacities. Most inverters in the 50 to 5,000-watt range fall into this category. High frequency switching type inverters are much lighter, generally smaller and less expensive than transformer type inverters.

For highest surge ratings, transformer based low-frequency inverters offer the best performance. Transformer inverters are built to handle surge ratings up to 300% for short periods and are necessary for applications like submersible well pumps, where you need either a very high surge capacity or to oversize the inverter above its typical usage, so that even at its maximum surge the inverter will not exceed its surge rating.

Pure sine wave or modified sine wave

Pure sine waves, generated naturally by rotating AC machinery are what your electricity company produces. Since all of the equipment sold on the market is designed for pure sine waves, you do the math. The two main types of inverters on the market are pure sine wave and modified sine wave. Pure sine wave inverters produce a higher quality of electricity, more like grid electricity than modified sine wave inverters, but some modified sine wave inverters can run almost all devices adequately.

Inverter manufacturers print spec sheets with information that includes info detailing specific inverters required for buildings, recreational vehicles, boats and portable devices. Spec sheets also include info about electrical standards to ensure the DC input voltage conforms to your electrical system, battery bank, as well as regional standards for AC utility service, which in North America are 115 and 230 volts.  To order your inverter products go to DC Direct Connect at http://www.dcdirectconnect.com/.