Power rating of Microwaves
The power rating of the microwave generally refers to the cooking power.
The electrical power consumed by the microwave will beapproximately 2 times the
cooking power. The
“surge power”
of the inverter should be 2 times the electrical
power (i.e., 4 times the cooking power). Please note that the surge power of the
microwave is not as long as the motor load and hence, the surge power of the inverter
can be considered to determine adequacy of meeting the starting surge power.
Powering a water supply pump
A water well or pressure pump often place the greatest demand on the inverter.
It warrants special consideration. Most pumps draw a very high surge of current during
start up. The inverter must have sufficient surge capacity to handle it while running
any other loads that may be on. It is important to size an inverter sufficiently, especially
to handle the starting surge (if the exact starting rating is not available, the starting surge
can be taken as 3 times the normal running rating of the pump). Oversize it still further
if you want it to start the pump without causing lights to dim or blink.
Idle power
Idle power is the consumption of the inverter when it is on, but no loads are running.
It is “wasted” power, so if you expect the inverter to be on for many hours during which
there is very little load (as in most residential situations), you want this to be as low
as possible.
Phantom and idling loads
Most of the modern gadgets draw some power whenever they are pluged in. Some of
them use power to do nothing at all. An example is a TV with a remote control.
Its electric eye system is on day and night, watvhing for your signal to turn the screen on.
Every appliance with an external wall-plug transformer uses power even when the
appliance is turned off. These little loads are called “phantom loads” because their
power draw is unexpected, unseen and easily forgotten.
A similar concern is “idling loads”. These are devices that must be on all the time in order
to function when needed. These include smoke detectors, alarm systems, motion detector
lights, fax machines, and answering machines. Central heating systems have a transformer
in their thermostat circuit that stays on all the time. Cordless (rechargeable) appliances
draw power even after their batteries reach a full charge. If in doubt, feel the device.
If it’s warm, that indicates wasted energy.
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