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SECTION 4 |
4.1 GENERAL DESCRIPTION
EVO
is a Pure Sine Wave, Bi-directional, Single-Phase Inverter / Charger with a Transfer Relay
TM
that operates either as an inverter OR as a smart battery charger. It uses a common Converter
Section that can work in two directions – in one direction it converts external AC input power to
DC power to charge the batteries using Grid / Generator (Charging Mode) and in the other direc-
tion, it converts DC power from the battery to AC power (Inverting Mode). This allows the same
power components to be used in both directions resulting in high-energy transfer efficiency with
fewer components. Please note that it can NOT work in both the directions at the same time (i.e.
it cannot work as an inverter and as a charger at the same time).
High performance 100 MHz DSP (Digital Signal Processing) type of micro-controller and Pulse
Width Modulated (PWM) conversion circuits are used for the above implementation.
4.2 COMPONENTS OF THE SYSTEM
It consists of 3 Sections – Inverter Section, Battery Charger Section and AC Input/Transfer Relay
Section. The unit is fed with the following inputs:
120 VAC / 60 Hz Grid input. Good quality Inverter Generator with stable 120 VAC / 60 Hz
–
output may also be used if Grid is not available.
DC Battery Source consisting of 12V/24V battery bank. - 4 versions of EVO
–
versions for 12 VDC battery input (EVO-1212F and EVO-1212F-HW) & 2 for 24 VDC battery
input (EVO-1224F and EVO-1224F-HW)
Additional external charging source: Solar Charge Controller of up to 50A capacity. The
–
output of the external Solar Charge Controller is routed through this unit and operates in
parallel with the internal charger. The current delivered by the external charge controller is
measured in real time. The internal charging current is controlled to ensure that the com-
bined current fed to the battery does not exceed the programmed Bulk Charging Current.
This improves the life of the battery. Please see Section 5.4 for more details.
4.3 INVERTER SECTION
The Inverter Section is a heavy-duty, continuous rated, DSP micro-controller based inverter gener-
ating a Pure Sine Wave output of 120 VAC, 60 Hz from the DC Battery Source. It is able to supply
AC power to various types of AC loads such as resistive loads (heaters, incandescent lamps etc)
or reactive loads (motors, air conditioners, refrigerators, vacuum cleaners, fans, pumps, Switched
Mode Power Supplies (SMPS) used in audio / video equipment and computers, etc.).
4.3.1 Principle of working of Inverter Section
The low DC voltage from the DC Battery Source is inverted to the AC voltage in two steps. The
low DC voltage from the DC Battery Source is first converted to low frequency (60 Hz), low volt-
age synthesized sine wave AC using an H-bridge configuration and high frequency PWM (Pulse
Width Modulation) technique. The low frequency, low voltage synthesized sine wave is then
stepped up to 120 VAC pure sine wave voltage using a low frequency Isolation Transformer and
filtration circuit. This type of DC to AC inversion is called Hybrid Type – a combination of low
frequency and high frequency implementation. Other distinctive features of the Inverter Section
are given below:
Soft Start: The inverter design incorporates "Soft Start" feature with the following advan-
tages and protections:
General Description & Principles of Operations
are available. 2
TM
SAMLEX AMERICA INC. | 71
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