Introduction
1 Introduction
1.1.1 Purpose of the Manual
This manual is intended to provide detailed information for the installation and operation of the option panel used in conjunction with a Trane variable frequency drive (VFD or drive). To enable efficient handling of the equipment, requirements are provided for installation of mechanical, electrical, control wiring, proper grounding, and environ- mental considerations.
1.1.2 Overview
A variable frequency drive regulates the speed and operation of an electric motor. The drive is programmable and offers many features and savings compared to operating a motor from unregulated line voltage. The option panel is a protective enclosure in which the drive and various optional components are assembled and mounted. The vertical non bypass panel is always configured with a disconnect switch and fuses to protect the drive. The vertical bypass panel allows switching between running the motor from the drive (variable speed) or across the line input power (constant speed).
The vertical bypass panel comes with one of two control options:
•The electromechanical bypass (EMB2)
•Electronically controlled bypass (ECB)
The EMB2 is operated by a selector switch on the front of the panel. The EMB2 controls a motor by switching between drive control, operation in bypass, or off. In addition, a test selection is available, which disengages the motor from the drive but keeps the drive operational while the motor runs in bypass. The switching function activates contactors to provide power to the motor through the drive or bypass circuitry, as required.
The ECB also uses contactors to provide power to the motor through the drive or bypass circuitry. However, the ECB contains a local processor that interacts with the drive’s control logic for programmable options, remote
inputs, and status reporting. The VFD’s logic circuitry is backed up by an independent
See more detailed descriptions of the EMB2 in 5 Electrome- chanical Bypass (EMB2) Operation and ECB in 6 Electronically Controlled Bypass (ECB) Operation of this manual.
1.1.3 Typical Bypass Operation
With contactors M1 and M2 closed and contactor M3 open, the motor is running in drive control. Opening contactor M2 removes power to the motor but allows the drive to remain under power. This is referred to as test mode. With contactors M1 and M2 open and contactor M3 closed, the motor is running in bypass from the line input power.
1.2 Bypass Circuits
1.2.1
The bypass circuit consists of a bypass contactor (M3) interlocked with a drive output contactor (M2), a drive input contactor (M1), and an overload relay. For the EMB2, a door mounted Drive/OFF/Bypass/Test Selector switch is used to electrically select whether the motor is powered by the drive, connected to the full speed bypass, or disconnected from both. The test position applies power to the motor through the bypass (M3 closed) contactor but removes power from the drive (M2 open) while keeping the drive powered (M1 closed). A Pilot light indicates when in bypass. For the ECB, control selection is made through the drive keypad by pressing the DRIVE BYPASS key and selecting from the available options shown. Display data indicates when in bypass. The circuitry may be supplied with either an input disconnect switch or an input circuit breaker.
