8 | SAMLEX AMERICA INC.
SeCTIOn 2 |
Features, Applications &
Principle of Operation
• Temperature controllers e.g.:
• Temperature Controlled Electric Blankets
• Devices using high capacitance based voltage multipliers for generating high
voltage (will create very high surge currents) e.g.:
• Photographic Strobe Lights
• Laser Printers
2.4.2 measuring modified Sine Wave voltage with a "true rmS"
voltmeter
As mentioned above, Modified Sine Wave voltage is a type of square wave that has an
RMS (Root Mean Square) value of 115 VAC in this Inverter. A general-purpose AC volt
-
meter is calibrated to accurately measure the rMS value of a Pure Sine Wave and NoT
of a Modified Sine Wave. If this general-purpose voltmeter is used to measure Modified
Sine wave voltage, it will indicate a lower value (96 VAC to 104 VAC). For accurately
measuring the voltage of a Modified Sine Wave, use a voltmeter which is designed to
measure “True RMS Values” like Fluke 87, Fluke 8060A, Fluke 77 / 99, Beckman 4410 etc.
2.5 principLe of operation anD cHarGinG aLGoritHm - Battery
cHarGer
The battery charger is a 2 Stage, Switched Mode Design using fly back Topology.
120 VAC from the AC Input is rectified to high voltage DC of around 170 VDC, which
is then converted to high frequency pulses using MoSfeT Switch and then stepped
down through switching transformer. The transformed voltage is rectified and filtered.
A sample of the output voltage is used as feedback signal for the drive circuit for the
switching Mosfet to achieve desired voltage regulation of 13.8 VDC using Pulse Width
Modulation (PWM). It is designed to provide maximum charging current of 15A.
2.5.1 charging / Discharging curves for Lead acid Batteries
fig. 2.2 shows the charging and discharging characteristics of a typical 12V / 24V flooded
Lead Acid battery at electrolyte temperature of 80°F / 26.7°C. The curves show the %
State of Charge (X-axis) versus terminal voltage (Y-axis) during charging and discharging
at different "C-rates".
please note that X-axis shows % State of charge. State of Dis-
charge will be = 100% - % State of charge.
The value of charging / discharging curent is
expressed as "C-Rate" which is a ratio as defined below
:
C-rate in Amperes
=
C
T
where,
C =
Capacity of the battery in Ampere Hours (Ah)
T = Time in Hours over which the battery in discharged from fully charged condition to
10.5V (12V battery) or 21V (24V battery) at constant current = C-Rate
e.g. if 100Ah
battery (C = 100) is discharged in 5 Hours (T = 5) the C-Rate =
100
5
= 20 Amperes
Summary of Contents for SAM Series
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