Yaskawa E7L Drive Bypass - Manual (Page 25)

Physical Installation 1 - 13
Contactors
The Bypass is a “2 contactor Bypass” circuit employing IEC rated contactors in an electrically interlocked arrangement to
allow mutually exclusive operation in Drive or Bypass modes. To minimize enclosure space requirements, they are mounted in
a 2 contactor assembly.
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
The OverLoad Relay (OLR) is mounted to the contactor assembly or back panel (depending on rating), just above the Bypass
contactor (see Figure 1.7). Electrically on the output power side of the Bypass unit, the adjustable thermal OLR provides
overload protection for the motor in both the Drive and Bypass operating modes. The Bypass three phase output power
connection to the motor is made to the output terminals of the overload relay. The OLR is set up in the factory to be a manual
reset device, requiring operator attention if an overload trip-out is experienced.
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 and selector buttons, as well as the control logic, have been incorporated into a
PCB assembly to eliminate the potential for loose wires after shipment and to control factory costs.
The operating elements are located on PCB A3, mounted to the inside of the enclosure door and ribbon cable connected to the
control logic PCB A2.
The control logic PCB A2 is mounted to the left hand side of the enclosure and contains the control circuit field wiring termi-
nal strips (TB1 through TB5).
Drive/Bypass logic interlocks explained
The Bypass 120 VAC logic circuit is interconnected with the Drive multi-function digital input terminals and multi-
function digital output terminals to allow a single customer interface to control both Drive and Bypass circuits. These Drive
terminals are therefore not available for other field use. All field control connections are landed at terminal strips TB1 through
TB5 on control logic PCB A2.
PCB Jumpers explained
J1 is a field configuration jumper to allow the user to select the internal 120 VAC power supply, a customer supplied 120 VAC
power supply or a customer supplied 24 VDC power supply for the digital inputs.
J2 and J3 are field configuration jumpers to allow the user to select the signal level (0 to 10 VDC or 4 to 20 mA) for the two
analog output signals.