Variable Frequency Drives
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Variable Frequency Drives Bypass Options - PowerPoint PPT Presentation

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Variable Frequency Drives Bypass Options. VFD Bypass Operation. Two Contactor Bypass. Power Supply. SED2 Drive. Mechanically Interlocked. Drive Output Contactor. Bypass Contactor. Motor. VFD Bypass Operation. Three Contactor Bypass. Power Supply. Optional Input Contactor. SED2

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VFD Bypass Operation

Two Contactor Bypass

Power Supply



Mechanically Interlocked

Drive OutputContactor

Bypass Contactor


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VFD Bypass Operation

Three Contactor Bypass

Power Supply




Mechanically Interlocked

Drive OutputContactor

Bypass Contactor


Optional “3rd” drive input contactor electrically isolates the VFD

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Bypass Types – Conventional and Electronic

  • Conventional bypass – uses hard-wired electrical components for mechanical bypass control

    • Switches

    • Fuses

    • Relays

  • Electronic bypass – electronic logic control with simple keypad

    • Reduced wiring and mechanical components

    • Improved system reliability

    • Additional logic features standard

      • Interlocked Start

      • 2 Safety circuits

      • Smoke Purge logic

Conventional Bypass

Electronic Bypass

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SED2 Conventional Bypass

  • VFD and Bypass cabinet mounted on common back plate

  • Conventional electromechanical control

    • Indicating lights, selector switches, relays

  • All voltages and HP ratings

  • Configurations available:

    • Disconnect (fused on non- fused)

    • NEMA 1 cabinet

    • 2 or 3 contactor control

    • manual/auto bypass selection standard

    • line/load reactor option

    • Damper end-switch logic option

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Conventional Bypass Components


Gland Plate

Conduit Connector

Mounting Back Plate

Bypass ON Indicator Light

Drive /Off / Bypass Selector

Line Disconnect

Drive Test Selector (3 contactor only)

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Conventional Bypass Components

Line reactor (optional)


Input contactor (optional)


Power fuses (optional)

Output contactor

Line disconnect

Bypass contactor


Field wiring terminals

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For more info, see the Bypass menu on this CD

Conventional Bypass Power Range

A-F denotes VFD frame size

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Electronic Bypass Features

  • Easy-touch keypad with status display

  • Common remote start/stop

  • Auto bypass

  • Essential service mode

  • Interlock start logic

  • Disconnect options

    • Disconnect

    • Fused Disconnect

    • Circuit Breaker

  • Two and three contactor models

  • 6 digital inputs and 6 digital outputs

  • Optional line or load reactor

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Electronic Bypass Components


Input contactor (optional)


Line reactor (optional)

Power fuses (optional)


Line disconnect


Bypass contactor


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Electronic Bypass Keypad

  • Easy-touch electronic keypad displays status and operating configuration

  • Indicates current status with 14 LEDs

  • Built -in logic reduces wiring and ensures safe operation

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Electronic Bypass Keypad Features

Indicates that input contactor is closed and drive has power.

Indicates input contactor is closed when on, close pending when flashing.

Toggling this button opens / closes the input contactor.

Enables hand bypass mode.

Enable remote bypass. Bypass light w/ flash. Contactor closes and light comes on when Remote Start input closes.

Enable closes both drive input and output contactors.

Essential service light flashes when this feature is activated.

Auto Bypass light flashes when this feature is activated.

Disconnect the motor whether in drive or bypass mode.

Indicates that one of the safety inputs is open.

Indicates that either the overload input has closed or that the thermal overload has tripped.

Indicates present operational state of interlocked start logic.

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For more info, see the Bypass menu on this CD

Electronic Bypass Power Range

A-F denotes VFD frame size

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Siemens SED2 VFD Advantages

  • Low harmonics design

  • Small enclosure size

  • Many standard features

  • Reduces operating cost

  • Low power losses/high efficiency

  • Minimal effect on customer power

  • Wide power range – from ½ to 125 HP