Damper control using PowerXL DH1 Variable Frequency Drives
Application Note
Effective March 2019
2.A) SW1 set to VFD position: The sequence of events:
a. The SW1 on the drive enclosure/panel is set to VFD position.
b. The BYPASS start is triggered from the Drives keypad. Optionally the switch on the
panel/enclosure wired to DI7 (Optional switch not shown in Figure:2).
c. The step b above will put the drive in Bypass mode (see Figure 1).
d. Trigger the start command to the drive like the start command to the drive in VFD
mode.
e. The start command to the drive will trigger RO3, initiating the damper motion.
f. After the damper position feedback is received the drive will close RO1, closing the
Bypass contactor and starting the motor.
Figure: 1 Showing Drive in Bypass mode
2.B) SW1 set to BYP position: The sequence of events
a. The SW1 is set to BYP position on the drive enclosure/panel.
b. The step a above will put the drive in Bypass mode (See Figure 1).
c. Trigger start command to the drive like the start command to the drive in VFD mode.
d. The start command to the drive will trigger RO3, initiating the damper motion.
e. Once the damper position feedback is received, the bypass contactor will close.
3) Bypass mode during Emergency Faults, damper is manually operated.
In an unlikely event of failure of the VFD control board (MCU), the user can start the motor
in the bypass mode by manually moving the damper to the required position.
Sequence of events in this emergency bypass mode are as below:
a. User to manually position the damper to the required position to provide the
required position feedback to run the motor.
b. After the user verifies that the required position feedback is available, user turns
the SW1 to the BYP position.
c. SW1 in BYP position closes the bypass contactor starting the motor.
3 EATON www.eaton.com
(Please note that the damper position feedback will also close RO1 but in this mode
the bypass contactor pick-up is not dependet on RO1 status)
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