Xantrex Technology 120 VAC/60 - Manual (Page 67)

OPERATION
 2001 Xantrex Technology, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. C: February 2001
Page
59
POWER VS. EFFICIENCY
There are two primary losses that combine to create the efficiency curve of the SW Series inverter. The
first is the energy that is required to operate the inverter at full output voltage while delivering no current.
This is the no load or idle power. At low power levels, the idle power is the largest contributor to efficiency
losses. At high power, the largest source of loss is a result of the resistance in the transformer and power
transistors. The power lost here is proportional to the square of the output power. For example, losses at
2000 watts will be four times higher than losses at 1000 watts. This graph represents a typical inverter’s
efficiency while operating resistive loads. Inductive loads such as motors are run less efficiently due to the
impact of power factor losses.
Figure 19, Trace™ SW Series Efficiency Curves
The SW Series offers an extremely good efficiency curve. The inverter reaches high efficiency at very low
AC load levels, which is important because the inverter often spends the majority of the time at the lower
power range. The high efficiency is maintained over a wide power range. Only when operating at high
power levels at or above the continuous power levels does the efficiency begin to drop off. Since this
usually only occurs for short periods of time, the impact may be negligible.
If your application involves the inverter powering heavy loads for significant periods of time, selecting a
model with a higher continuous power rating and a higher DC input voltage would improve the operation of
the system. Since the low power efficiency of all the SW Series is extremely good, oversizing the inverter
does not reduce system performance.
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