Samlex America SAM-800-12 - Manuel (Page 6)

4 | SAMLEX AMERICA INC.
SECTION 2 | Introduction
Load controlled cooling fan
Cooling is carried out by convection and by forced air circulation by load-controlled fan.
The fan will normally be off and will be switched oN automatically at the following
loads:
• SAM-250-12 and SAM-450-12:
At load of 8W to 12W
• SAM-800-12: At load of 35W to 45W
This will reduce energy consumption by the fan and will increase overall efficiency
principle of operation
Conversion of 12 VDC from the battery / other DC source to 115 VAC takes place in 2
stages. In the first stage, the 12 VDC is converted to high voltage DC (around 160 VDC)
using high frequency switching and Pulse Width Modulation (PWM) technique. In the
2nd stage, the 160V high voltage DC is converted to 115V, 60 Hz Modified Sine Wave AC.
(Note: 115V is the RMS value of the Modified Sine Wave AC voltage. The peak value of
the Modified Sine Wave AC voltage will be equal to the value of the above high voltage
of around 160V. See the fig 2.1 below)
modified Sine Waveform -
characteristics & comparison with pure Sine Waveform
Please refer to Fig 2.1 below which shows one cycle of Modified Sine Wave and
Pure Sine Wave for comparison.
Fig 2.1 Modified Sine Wave and Pure Sine Wave - Comparison
TIME
180
160
140
120
100
80
60
40
20
0
20
40
60
80
100
120
140
160
180
Modified Sine
Wave sits at
0V for some
time and then
rises or falls
Sine Wave
Modified Sine Wave
Pure Sine Wave
crosses 0V
instantaneously
Legend
V +
V -
115 RMS