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Introduction
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.
MAIN DISCONNECT
L1
1L1
INPUT
Fuse
L2
1L2
POWER
Fuse
L3
1L3
Fuse
DS1
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.
Vertical Bypass/Non Bypass Panel
EARTH
GROUND
M1
2L1
3L1
Fuse
L1/91
Type 1 Enclosure
2L2
3L2
Fuse
L2/92
2L3
3L3
Fuse
L3/93
MK903
MK902
MK904
24 V DC SMPS
MK901
1
2
3
4
5
6
7
8
-
+
®
MG.13.A1.22 - VLT
is a registered Danfoss trademark
Control Features
Safety Interlock
Common Start / Stop
Automatic Bypass
Run Permissive
Basic Fire Mode
Advanced Fire Mode
Serial Communication
Table 1.2 Bypass Configurations
VFD
2T1
U/96
2T2
V/97
2T3
W/98
EARTH
GROUND
CONTROL
TRANSFORMER
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
EMB2
ECB
X
X
X
X
X
X
X
X
X
X
X
X
CUSTOMER
SUPPLIED
OL1
M2
AC MOTOR
1T1
T1
1T2
T2
1T3
T3
M3
1-3
1
1
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