Yaskawa AC Drive Z1000 AC Drive HVAC Fan - Manual (Page 144)

u S4: Bypass Operation
The Drive/Bypass functionality allows the drive to control contactors that switch the motor voltage source between the drive
and line voltage. A digital input can force the drive to go into Bypass mode and cause the motor to run on line voltage (full
speed).
A second digital input (override) will run the motor on line voltage provided that dampers open feedback is present. The drive
can switch to running the motor on line voltage if a fault occurs in the drive and also be configured to switch to Bypass for
energy saving purposes if it is running near full speed for a set amount of time.
n Enabling Programmable Bypass Logic
The programmable bypass logic is enabled when the following digital inputs are assigned: A4 (BP Emergency Override), A5
(BP Drive/Bypass Select), and A7 (BP Customer Safeties), and the following digital outputs are assigned:
A4 (BP Drive Relay Contact), and A5 (BP Bypass Relay Contact)
Note: 1. If o1-16 or o1-17 are set to 2 (Drive/Bypass), it is not necessary to set digital output A5.
2. If o1-16 or o1-17 are set to 3 (Bypass Run Command), it is not necessary to set digital output 84.
When Bypass functionality is enabled, the drive can allow the motor to run off of line voltage instead of the drive output. The
drive will only run in Drive or Bypass mode if a Run command is entered. The drive must also be configured to 2-Wire control
to enable Bypass functionality. Each time the drive performs a switch from Drive mode to Bypass mode it will follow the
procedure outlined below.
Immediate Transfer to Bypass
Three conditions: Emergency Override (Smoke Purge), Transfer on Fault Required, and Energy Saving Transfer, require the
drive to perform an immediate transfer to bypass.
To protect system hardware, this transfer cannot happen instantly. When an immediate transfer is required, the drive will block
the output. After the L2-03 time (Minimum Baseblock Time) elapses, the BP Drive Relay Contact opens to disconnect the
drive from the motor. The drive then allows the Minimum Baseblock Time (L2-03) to elapse before closing the BP Bypass
Relay Contact. This causes the motor to operate on line voltage.
This process ensures that any residual field present in the motor is allowed to dissipate before the voltage source is changed.
Transfer to Drive Operation
When this occurs, the drive will open the BP Bypass Relay Contact, wait until the Minimum Baseblock Time (L2-03) elapses,
close the BP Drive Relay Contact and wait for the L2-03 time to elapse again. After the drive is connected to the motor, it will
remove the Baseblock condition, perform a speed search, catch the spinning motor, and ramp to the desired output frequency.
n Programmable Bypass Logic
When the Drive/Bypass MFDI (H1-oo = A5) is closed and a Run command is entered, the drive switches to Drive mode
and allows the drive to run the motor. Refer to Transfer to Drive Operation on page 144 for details.
If the Drive/Bypass Select digital input is opened and the Bypass Run command is given, the drive switches to Bypass mode
and allows the motor to run on line voltage. Refer to Immediate Transfer to Bypass on page 144 for details.
When Drive/Bypass MFDI (H1-oo = A5) is open, but no Run command is present, the HOA keypad displays “Bypass Select
Off”.
When Drive/Bypass MFDI (H1-oo = A5) is open and the BP Bypass Relay Contact is closed, the HOA keypad displays
“Bypass Select Run”.
When o1-16 or o1-17 is set to 2 (Drive/Bypass), the HOA keypad DRV/BYP multi-function key selects the bypass operating
mode instead of the Drive/Bypass MFDI.
When o1-16 or o1-17 is set to 3 (Bypass Run Command), the HOA keypad RUN BYP multi-function key is used to run in
Bypass mode instead of the Bypass Run Command MFDI.
Safety Circuit
The Customer Safeties Relay must to be closed for drive or bypass operation to be functional. If the Customer Safeties Relay
is open, the drive will not run in Drive or Bypass mode.
The Customer Safeties Alarm “SAFE Customer Safety” displays when the BP Customer Safeties MFDI (H1-oo = A7) is
open.
1.11 S: Special Parameters
144 YASKAWA ELECTRIC SIEP YAIZ1U 03A YASKAWA AC Drive – Z1000 Programming Manual