Trane Vertical Bypass/Non Bypass Panel Bypass Platform Configurations, Switch Mode Power Supply

Introduction

1.4 Bypass Platform Configurations

The two bypass platform configurations are ECB and EMB2. The features available as options with each platform are listed in Table 1.2. The ECB, also listed below, has all option features available. See 5 Electromechanical Bypass (EMB2) Operation for additional details on the EMB2 and

6 Electronically Controlled Bypass (ECB) Operation for the ECB.

Control Features	EMB2	ECB
Safety Interlock	X	X
Common Start / Stop	X	X
Automatic Bypass	X	X
Run Permissive	X	X
Basic Fire Mode	X	X
Advanced Fire Mode		X
Serial Communication		X

Table 1.2 Bypass Configurations

Figure 1.2 Basic Bypass Circuit

1.5 Switch Mode Power Supply

The VFD’s logic circuitry is backed up by an independent panel-mounted switch mode power supply so if the drive loses power, control and communication functions are maintained. The SMPS converts three-phase AC input power to 24 V DC control power. Since the SMPS draws power from all three phases, it offers immunity protection from most phase-loss and brown-out conditions. The SMPS is internally protected from short circuit on its output and three board-mounted fuses provide additional protection. The SMPS is not designed for external use and may take up to 5 sec. to initialize at power-up. The SMPS will maintain a 24 V DC output with a low input line voltage. The 200 Volt SMPS will maintain the 24 V DC output with a line voltage as low as 150 V AC and the 600 V SMPS to 335 V AC. Refer to Figure 1.2.

1.5.1 Control Transformer

A control transformer is included on larger horsepower units where the contactor coils are AC. The control transformer steps down the line input voltage to 120V AC. The coils of AC contactors are isolated from the Switch Mode Power Supply via relays.

1.6 Disconnects

1.6.1 Main Disconnect

The main disconnect removes line input power to the drive and bypass. A main disconnect is available in four options.

•Fused disconnect. Two-position (ON/OFF) rotary switch, padlock compatible, with three fuses, one on each phase, built into the switch. For safety, the switch must be in the OFF position before

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