Typical Bypass Operation - Trane TR200 Operating Instructions Manual

The ECB also uses contactors to provide power to the motor through the drive or bypass circuitry. However, the
ECB contains a local processor which interacts with the drive's control logic for programmable options, remote
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. Program-
ming and display are provided by the VFD's keypad. 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 EMB in Sections 5 and ECB in Section 6 of this manual.

Typical bypass operation

With contactors M1 and M2 closed and contactor M3 open (see the following figure (
functions )), 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 the test mode and only available in the three-contactor configuration
shown. With contactors M1 and M2 open and contactor M3 closed, the motor is running in bypass from the line
input. For a two-contactor configuration, M1 is absent. In this case, contactors M2 and M3 control the options
for running in drive or bypass mode. The drive disconnect and fuses shown in the figure are controlled by an
ON/OFF disconnect on the bypass panel.
Bypass Circuits
Two-contactor bypass.This bypass consists of motor starter circuitry used in bypass, a bypass contactor (M3)
interlocked with a drive output contactor (M2) mounted in the bypass enclosure. For the electromechanical
bypass (EMB), an enclosure-mounted Drive/OFF/Bypass selector is used to electrically select whether the motor
is controlled by the drive, connected to the full-speed bypass, or disconnected from both. The contactor and
motor starter are controlled by this switch. A light indicates when in bypass. For the electronically controlled
bypass (ECB), control selection is made through the drive keypad by pressing the DRIVE BYPASS key and se-
lecting from the available options shown. Display data indicates when in bypass. A drive disconnect is also
available with the two-contactor bypass and is required for the option panel components without bypass.
Three-contactor bypass.This bypass consists of motor starter circuitry used in bypass, a bypass contactor (M3)
interlocked with a drive output contactor (M2), a drive input contactor (M1), and an overload relay mounted in
the option panel. For the EMB, an enclosure mounted Drive/OFF/Bypass/ Test switch is used to electrically select
whether the motor is driven by the drive, connected to the fullspeed bypass, or disconnected from both. The
test position applies power to the motor through the bypass (M3 closed) while removing power to the motor
(M2 open) but keeps the drive powered (M1 closed). A 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 dis-
connect switch or an input circuit breaker.
Contactor Drive Mode
M1 Closed
M2 Closed
M3 Open
Table 1.2
Illustration 1.1: Basic 3-contactor Bypass Functions
TR200 Option Panel Operating Instructions
OFF Bypass Mode
Open Open
Open Open
Open Closed
Introduction
Basic 3-contactor bypass
Test Mode
Closed
Open
Closed
5