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1.4 Bypass Platform Configurations
The two bypass platform configurations are ECB and EMB2.
The features available as options with each platform are
listed in Table 1.2. The ECB, also listed below, has all option
features available. See 5 Electromechanical Bypass (EMB2)
Operation for additional details on the EMB2 and
6 Electronically Controlled Bypass (ECB) Operation for the
ECB.
Control Features EMB2 ECB
Safety Interlock X X
Common Start / Stop X X
Automatic Bypass X X
Run Permissive X X
Basic Fire Mode X X
Advanced Fire Mode X
Serial Communication X
Table 1.2 Bypass Configurations
Figure 1.2 Basic Bypass Circuit
1.5 Switch Mode Power Supply
The VFD’s logic circuitry is backed up by an independent
panel-mounted switch mode power supply so if the drive
loses power, control and communication functions are
maintained. The SMPS converts three-phase AC input
power to 24 V DC control power. Since the SMPS draws
power from all three phases, it offers immunity protection
from most phase-loss and brown-out conditions. The SMPS
is internally protected from short circuit on its output and
three board-mounted fuses provide additional protection.
The SMPS is not designed for external use and may take
up to 5 sec. to initialize at power-up. The SMPS will
maintain a 24 V DC output with a low input line voltage.
The 200 Volt SMPS will maintain the 24 V DC output with
a line voltage as low as 150 V AC and the 600 V SMPS to
335 V AC. Refer to Figure 1.2.
1.5.1 Control Transformer
A control transformer is included on larger horsepower
units where the contactor coils are AC. The control
transformer steps down the line input voltage to 120V AC.
The coils of AC contactors are isolated from the Switch
Mode Power Supply via relays.
1.6 Disconnects
1.6.1 Main Disconnect
The main disconnect removes line input power to the
drive and bypass. A main disconnect is available in four
options.
•
Fused disconnect. Two-position (ON/OFF) rotary
switch, padlock compatible, with three fuses, one
on each phase, built into the switch. For safety,
the switch must be in the OFF position before
Introduction
BAS-SVX49A-EN 1-3