Allen-Bradley 520F-BOD Bulletin520F 2-Speed Motor Starter Unit

Module Feature

520F-BOD belongs to Bulletin 520F NEMA two-speed consequent pole motor starter manufactured by Allen-Bradley (Rockwell Automation). NEMA Size1 open type assembly,control coil rated 115~120V,60Hz. It adopts eutectic alloy thermal overload relay for motor overcurrent protection. Contains low-speed contactor,high-speed contactor plus mechanical interlock to prevent both contactors closing simultaneously. Auxiliary contacts provide status feedback and interlock signal for PLC or hardwire control. Designed for consequent pole two-speed induction motors. Widely used for dual-speed fans,water pumps,conveyors and machine tool motor control.

Working principle

Low speed contactor energizes for low RPM operation; high speed contactor energizes for high RPM operation. Mechanical interlock prevents simultaneous closing of high/low speed contactors to avoid short circuit. Eutectic alloy overload relay continuously monitors motor current and trips to cut off power upon overload. Auxiliary contacts output running status and fault alarm signals to external control system.

Onboard components

Low speed main contactor,high speed main contactor,mechanical interlock assembly,auxiliary contact set,115-120V 60Hz coil assembly,eutectic alloy thermal overload relay,power terminal block,control terminal block,metal mounting base plate.

LED indicators

No built-in LED indicators; status feedback comes from auxiliary contact signal to external control cabinet.

Hardware self-diagnosis

Contact wear inspection,coil continuity resistance test,overload relay trip function test,mechanical interlock function check,wiring short circuit detection.

Programming software

No dedicated programming software,controlled by external PLC or hardwired relay logic.

Electrical & Process Parameters

Model:520F-BOD Brand:Allen-Bradley Device type:Bulletin520F NEMA Size1 Consequent Pole 2-Speed Motor Starter NEMA frame:Size1 Control coil:115~120V,60Hz Motor type:Consequent pole two-speed 3-phase motor Interlock:Mechanical interlock between high speed and low speed contactor Overload:Built-in eutectic alloy overload relay Cooling:Natural convection cooling Protection:Thermal overload protection; short circuit protection via external fuse or circuit breaker

Mechanical & Structure

Mounting:Back plate mounting inside control cabinet Protection class:Open type IP00 bare assembly Housing:No enclosure,metal base plate

Environmental

Operating temperature:-10℃ ~ +40℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non-condensing Certification:CE,UL compliant Status: Allen-Bradley Bulletin520F open two-speed starter for consequent pole dual speed motor

Installation

Follow strict ESD safety procedure before handling.Mount base plate firmly inside control cabinet.Connect three-phase main power and two-speed motor cable to main power terminals.Wire control circuit to coil and auxiliary contacts.Set overload relay trip current matching motor FLA before commissioning.Verify mechanical interlock action before power on.

Interface

Main power input terminal,motor multi-tap output terminal,coil control terminal,auxiliary contact terminal.

Diagnostic

Coil cannot pull in:coil burnout or missing 115-120V control voltage. Cannot switch speed:stuck mechanical interlock or auxiliary contact interlock fault. Overload trip:motor overload,locked rotor or incorrect FLA setting. Contact arcing:motor short circuit or excessive starting current.

Product Brief

Allen-Bradley 520F-BOD Bulletin520F NEMA Size1 open type two-speed consequent pole motor starter,115-120V 60Hz control coil,built-in eutectic alloy thermal overload relay,mechanical interlock design for dual-speed fan,pump and conveyor motor speed switching control.