Bypass Unit Information - Emerson EVH Series Installation Manual

Bypass Unit Information

All products are enclosed VFDs that convert 3-phase AC input power into 3-phase output power for controlling motors.
Some configurations incorporate bypass circuits. All models are enclosed in either a wall-mounted or a floor standing
enclosure using Metal or Plastic cover designs. All models contain a short-circuit protective device, fuses, thermal-magnetic
circuit breaker or compact motor controller (CMC), and an associated disconnect handle/operator. All designs are suitable for
use in compartments handling conditioned air. These devices may be marked for "Service Entrance". Operating Mode
defines the type of motor control: VFD or Bypass. VFD is when the motor is under speed control from the VFD, Bypass is
when the motor is run "across the line" at fixed/full base speed.
Control mode defines the method/source used to start the motor and control the speed of the motor when operating on the
VFD. The VFD can be programmed for many methods but the default control mode is HAND-OFF-AUTO. The default setup
is that the HAND-OFF-AUTO selection is made from the Keypad Buttons. Other selection programming is available.
A bypass unit contains a VFD drive with a 24 Vdc bypass control circuit. It also includes 24 Vdc power supply and 24 Vdc
VFD output and bypass contactors.
Input Device Choices: MMP, CB, Non-fusible disconnect with separately mounted fuses
Operator Controls: VFD Keypad only.
Optional: 3-position VFD-OFF-BYPASS selector switch and VFD Keypad
Operation Modes: Without the selector switch option, the operation mode is selected by the keypad as: Bypass, Off or VFD
With the selector switch option: The mode is determined by the selector switch on the front of the unit. VFD position– the
keypad determines the mode as described above.
BYPASS position–Forced Bypass mode – motor starts in bypass immediately. OFF position – Force off mode
Control Modes: Start/Stop of VFD or Bypass: Via the VFD keypad HOA keys and remote run contacts wired directly to VFD
logic PCB
Speed Ref for VFD: HOA operation: via VFD keypad or remote speed signal wired to VFD logic PCB
Bypass Options: VFD Isolation contactor or VFD isolation switch or VFD isolation fuses
Light option: Single Multi-color pilot light: VFD Run, VFD Fault, Bypass Run and Bypass Run and VFD faulted.
Component locations
Typical locations of key components are shown on the connection diagram provided with the unit. Some examples are shown
below.
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