PROBING MYSTERIES OF THE INVERTER: PART I

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

I'd like to stress, at this point, that the power factor of an inverter itself doesn't affect its efficiency ... it merely changes the unit's rating. For example, a 4-KW inverter with a power factor of 0.5 is rated at 8 KVA. This doesn't mean that only half the power is being delivered to the load, though, since if the power factor were corrected to unity (using capacitance), the unit's capability would still be 4 KW.

WIRE NUTS AND BOLTS. Unfortunately, tying into a utility isn't as easy as it may first appear. Whether you use a self- or line-commutated inverter, there are important safety considerations to be taken into account. The self-commutated inverter, for instance, would keep right on humming if the utility lines went dead. This could have several serious consequences. First, if the disruption were caused by a component failure—such as a transformer—the inverter would feed power into the defect, which could wreak havoc. At the same time, a service worker could conceivably receive a lethal shock while trying to repair equipment that was supposedly "dead".

In theory, at least, a line-commutated inverter should stop working if the utility power is removed. This should protect the grid from independent producers ... unless more than one such plant is on the line. You see, it's not impossible for two, or more, inverters to synchronize between themselves and continue producing power.

A synchronous inverter, therefore, must include a sensor to disconnect it from the grid when even one cycle (1/60 of a second) is missed. Actually, though, it's not unusual for a utility to skip a beat now and then, because of the many switching stations such firms employ to manage power flow. So the inverter's "fail safe" detector must be smart enough to judge the difference between a slight case of the jitters and an honest-to-goodness failure.

Living in an AC world may not be the best (or the worst) of all possibilities, but it is one that we all have to deal with. Through the proper use of an inverter, DC and AC power can be made compatible—and cost-effective—though ... and, for many of us, it may be the only practical method of having our electricity and using it too.

EDITOR'S NOTE: In the next issue ofMOTHER, we'll tell you how to go aboutselecting, sizing, and using inverters. Don'tmiss it!

RSS | Comments | E-mail | Print