Appendix a - mch with bypass option, A.1 mch operation with bypass – Lenze MCH Series User Manual
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APPENDIX A - MCH WITH BYPASS OPTION
A.1
MCH OPERATION WITH BYPASS
The MCH Series drive is available with a Bypass option that allows the motor to be
operated at full speed from line power while the drive is being serviced. The Bypass
option contains three contactors. Two are used to isolate the drive while in bypass
mode. One isolates the drive from input power, and the other isolates the drive output
from the motor. The third contactor is used to start the motor across line power.
The bypass option contains three selector switches: HAND/OFF/AUTO, DRIVE MODE/
OFF/BYPASS MODE and DRIVE TEST/OFF/DRIVE NORMAL.
HAND/OFF/AUTO - In HAND mode, the drive or bypass will start.
In AUTO mode, the drive or bypass will start when terminal B3 is closed to B4 on
TB50. Drive or Bypass mode is selected using the DRIVE MODE/OFF/BYPASS
MODE switch.
When configured with the Bypass option, the HAND (START), and AUTO (START)
keys on the drive's keypad are disabled and cannot be used to start the drive. The
OFF (STOP) key will still function to stop the drive.
If an MCH drive with bypass is running in drive mode, and is stopped using the OFF
(STOP) key on the drive's keypad instead of the OFF position on the H/O/A selector
switch, the drive cannot be started again until the HAND (START) or AUTO (START)
key on the keypad is pressed to reset the OFF (STOP) command from the keypad.
DRIVE MODE/OFF/BYPASS MODE - In DRIVE MODE, the MCH drive controls the
motor (the MCH input and output contactors are closed).
In BYPASS MODE, the bypass contactor is used to start and stop the motor (the
MCH input and output contactors are open).
DRIVE TEST/OFF/DRIVE NORMAL - In DRIVE TEST mode, input power is applied to
the drive for testing purposes, but the output contactor remains open to isolate the
drive from the motor.
In DRIVE NORMAL mode, the input and output contactors are closed, allowing the
drive to control the motor.
NOTE 1:
If any of the three selector switches is in the OFF position, the motor cannot
be operated.
NOTE 2:
When the drive is equipped with the bypass option, motor rotation must be
checked in both drive mode and bypass mode. Refer to NOTE 2 in Section
12 for the procedure for checking and correcting motor rotation.