Mechanical Installation
2
2.4 Bypass Components
YASKAWA SIEPYAIH6B01A HV600 AC Drive Bypass Technical Reference 37
2.4 Bypass Components
◆ Input Disconnect Switch
Electrically located on the input power side of the bypass, the door mounted rotary input disconnect switch provides a
way to disconnect bypass from line power for equipment maintenance. Put the disconnect in the OFF position to open
the bypass enclosure door. When open, you can use a padlock to lock the handle in the OFF position. The customer
must supply branch short circuit protection for the bypass.
◆ Contactors
The bypass is a 2-contactor or 3-contactor bypass circuit employing IEC rated contactors in an electrically interlocked
arrangement to allow mutually exclusive operation in Drive or Bypass modes.
The control logic and “soft start” characteristic of the drive limit the drive input and output contactors to motor FLA
current or less. For this reason, the drive output contactor has a lower current rating than the bypass contactor. The
bypass contactor is exposed to motor inrush current (LRA) when starting the motor across-the-line and therefore
requires a higher current rating.
◆ Overload Relay
Electronic overload relay consists of bypass relay board and two pass-through current transformers. Overload relay
functions, settings, adjustments and reset operations are done through the keypad. The bypass three-phase output
power connection to the motor is made to terminal block TB3.
◆ Control Power Transformer
A Control Power Transformer (CPT) is provided to power the bypass 120 Vac control circuit. The VA capacity is
determined by the control circuit and optional functions specified for the unit. The CPT primary is fused in both legs,
the secondary is fused when required by NEC (transformer VA and wire size dependent). One side of the transformer
secondary is grounded to the bypass enclosure.
◆ Electronic Bypass Control Logic
Operating elements such as indicating LEDs, selector buttons, and control logic are incorporated into a PCB assembly
to eliminate the potential for loose wires after shipment.
The operating elements are located on PCB A3 and the control logic PCB A2 is mounted to the left-hand side of the
enclosure and contains the control circuit field wiring terminal blocks TB1 through TB5.
◆ Drive/Bypass Logic Interlocks
The bypass 120 Vac logic circuit is interconnected with the drive multi-function digital input terminals and
multifunction digital output terminals to allow a single customer interface to control both drive and bypass circuits.
These drive terminals are not available for field connections. All field control connections are landed at terminal
blocks TB1 through TB5 on control logic PCB A2 and drive PCB A1.
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