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Introduction
1 Introduction
1.1.1 Purpose of the Manual
This manual is intended to provide detailed information for
the installation and operation of the vertical panel used in
conjunction with a Danfoss variable frequency drive (VFD).
To enable efficient handling of the equipment,
requirements are provided for installation of mechanical,
electrical, control wiring, proper grounding, and environ-
mental considerations. Pre-start and start up procedures
are detailed. Also included is a detailed overview of the
panel bypass function. In addition, identification of other
optional components and their operation and start up
troubleshooting instructions are included. For the electron-
ically controlled bypass, additional programming and
operation information is provided.
1.1.2 Overview
A variable frequency drive regulates the speed and
operation of an electric motor. The drive is programmable
and offers many features and savings compared to
operating a motor from unregulated line voltage. The
panel is a protective enclosure in which the drive and
various optional components are assembled and mounted.
The vertical non bypass panel is always configured with a
disconnect switch and fuses to protect the drive. The
vertical bypass panel allows switching between running
the motor from the drive (variable speed) or across the line
input power (constant speed).
The vertical bypass panel comes with one of two control
options:
•
The electromechanical bypass (EMB2)
•
Electronically controlled bypass (ECB)
The EMB2 is operated by a selector switch on the front of
the panel. The EMB2 controls a motor by switching
between drive control, operation in bypass, or off. In
addition, a test selection is available, which disengages the
motor from the drive but keeps the drive operational while
the motor runs in bypass. The switching function activates
contactors to provide power to the motor through the
drive or bypass circuitry, as required.
The ECB also uses contactors to provide power to the
motor through the drive or bypass circuitry. However, the
ECB contains a local processor that interacts with the
drive's control logic for programmable options, remote
Vertical Bypass/Non Bypass Panel
inputs, and status reporting. The VFD's logic circuitry is
backed up by an independent panel-mounted power
supply so that, even if the drive loses power, control and
communication functions are maintained. Programming
and display are provided by the LCP. An important feature
of the ECB is the ability to accept commands from a
building automation system (BAS) and to report
operational status in return.
See more detailed descriptions of the EMB2 in 5 Electrome-
chanical Bypass (EMB2) Operation and ECB in 6 Electronically
Controlled Bypass (ECB) Operation of this manual.
1.1.3 Typical Bypass Operation
With contactors M1 and M2 closed and contactor M3
open, the motor is running in drive control. Opening
contactor M2 removes power to the motor but allows the
drive to remain under power. This is referred to as test
mode. With contactors M1 and M2 open and contactor M3
closed, the motor is running in bypass from the line input
power.
1.2 Bypass Circuits
1.2.1 Three-contactor Bypass
The bypass circuit consists of a bypass contactor (M3)
interlocked with a drive output contactor (M2), a drive
input contactor (M1), and an overload relay. For the EMB2,
a door mounted Drive/OFF/Bypass/Test Selector switch is
used to electrically select whether the motor is powered
by the drive, connected to the full speed bypass, or
disconnected from both. The test position applies power
to the motor through the bypass (M3 closed) contactor but
removes power from the drive (M2 open) while keeping
the drive powered (M1 closed). A Pilot light indicates when
in bypass. For the ECB, control selection is made through
the drive keypad by pressing the DRIVE BYPASS key and
selecting from the available options shown. Display data
indicates when in bypass. The circuitry may be supplied
with either an input disconnect switch or an input circuit
breaker.
®
MG.13.A1.22 - VLT
is a registered Danfoss trademark
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