Hubbell Euclid 4291 User Manual

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Hubbell Industrial Controls

 

Euclid™ Lifting Magnet Controller

4291

Varistor Type Automatic Discharge

 

Specification 4291 • May 2004 • Replaces July 1990

General Information

The Euclid Type 4291 Magnet Controller is for use with all types and makes of lifting magnets. It assures fast and clean release of all types of magnet loads.

All or just part of the load may be dribbled, if desired. In addition, because of the circuit design, the magnet and magnet leads are not subjected to high induced voltages.

Automatically discharges magnet.

Fast and clean release of load.

Peak magnet induced voltage limited to under 700 volts.

Wide reverse current adjustment for different types of magnet loads.

Mechanically interlocked mill-type“Lift” and “Drop” contactors.

High-thermalcapacity varistor discharge.

Permanently connected discharge path.

Discharge path completely independent from the line.

“Drop” contactor opens automatically at end of drop cycle.

Front wired, front removable components.

Long contact life.

Minimum maintenance.

Full voltage reverse current.

NEMA 3R Enclosed

Application

Euclid Type 4291 Lifting Magnet Controllers have many uses from light scrap handling to extremely heavy plate or billet handling. The flexibility of this magnet controller is illustrated by the ease of proper “cleaning” that can be accomplished when switching from one type of material to another. A simple adjustment of the potentiometer (P1) is all that is necessary. An inherent dribble characteristic is designed into each unit allowing material sorting such as steel plate stacking, by releasing one plate at a time.

Description

The Euclid Type 4291 Magnet Controller incorporates time proven components arranged to provide a new concept in magnet controller design and operation.

This controller includes all necessary power and reverse current contactors in addition to discharge path components.

Euclid’s standard mill-typecontactors are used to carry the power to the magnet. The

Euclid Lifting Magnet Controllers Provide 3-WayRelease of Load

Euclid Type 4291 automatic discharge type magnet controller is the only one on the market today that will assure (1) fast and clean release of full load, (2) accurate release of partial load and (3) precise control of dribbling. It can be used with all types and makes of lifting magnets in any industrial application.

reverse current or “Drop” contactor is also a mill-typecontactor. The commonly used discharge resistor has been replaced by a high thermal capacity varistor connected in series with a silicon rectifier to assure a permanently connected independent discharge path at all times around the magnet.

Main power of “Lift” contactors, due to the circuit design described herein, need only Euclid’s exclusive arc-centering,high-arcinterrupting system to handle the highly inductive magnet circuit.

The high thermal capacity of the nonlinear varistor dissipates the energy stored in the magnet at a much lower value of induced voltage than does the usual fixed type discharge resistor. The varistor assembly is a bank of silicon-carbidecomposition discs connected in parallel and cooled by aluminum radiating plates.

The maximum induced voltage permitted by the varistor is a peak of 700 volts. This feature assures extra protection of the magnet and lead system insulation. It also minimizes destructive arcing on the "Lift" contactor.

Non-linearcharacteristics of the varistorhelp maintain the discharge voltage at the maximum allowable voltage until all of the

stored magnet energy is dissipated. The Euclid Type 4291 Magnet Controller dissipates stored energy as fast as any comparable device, but with a much lower induced voltage. It is not necessary to close the "Drop" contactor immediately to provide a discharge path.

Full line voltage, for cleaning the magnet, is applied to the magnet terminals when the value of the induced magnet voltage declines to nearly the line voltage value. Resistors are eliminated from the reverse current circuit. This allows the reverse current to build up as fast as the magnet inductive characteristics will permit.

During the time of the stored energy dissipation, the reverse voltage across the magnet and the discharge varistor assembly signals the discharge Sensor Module (DSM) that the discharge cycle has begun. When the discharge voltage falls to 250 to 300 volts, the "DSM" closes a pilot Drop Relay (DR) that energizes the Drop Contactor (D).

The adjustable time reverse current cycle begins with the closing of the Drop Relay after practically all the stored magnet energy is dissipated by the Discharge Varistor (DVA) assembly. The DSM also controls the length of the reverse current cycle. After a preset

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Euclid Lifting Magnet Controllers: Automatic Discharge

Specifications 4291

period, controlled by the Potentiometer (P1) assembly, the DSM de-energizesthe Drop Relay. This causes the Drop contactor to open and end the reverse current cycle.

The remaining reverse magnet current flows through a secondary discharge path from the magnet through the normally closed "power auxiliary" interlock of 2L, the DVA and back to the magnet.

The Euclid magnet controller can be operated by a small notched position master switch or a maintained contact-typepushbutton station.

The arrangement of the circuit components allows an operator to drop portions of a load with ease. This is a feature most operators will appreciate. A portion of the load can be dropped by merely moving the master switch only the distance necessary to momentarily de-energizethe "Lift" contactor. This feature is possible because of the permanently connected discharge path and the elimination of having to close the "Drop" contactor before opening the "Lift" contactor.

FANNING PACKAGE includes Fanning Contactor and Fanning Resistor for separate

mounting suitably enclosed for NEMA 2 or NEMA 3R service.

Fanning is the insertion of a resistor discharge path in parallel with the DVA to give extended magnet discharge time that is activated by a separate fanning pushbutton. The operator is allowed to control the rate of magnet discharge, dropping all or part of the load, by activating the fanning control. Releasing the fanning pushbutton deactivates the fanning control and returns the magnet controller to the lift mode to retain the remaining magnet load.

Comparison ChartSchematic Diagram

Schematic Diagram

Symbol

Function

Symbol

Function

DR

DROP RELAY

MOV

SURGE SUPPRESSOR

PI

POTENTIOMETER ASSEMBLY

DVA

DISCHARGE VARISTOR

CFU

CONTROL FUSE

DSM

DISCHARGE SENSOR MODULE

RFU

DROP FUSE

D

DROP CONTACTOR

DI

DIODE

2L

LIFT CONTACTOR

RECT

RECTIFIER, MAGNET DISCHARGE PATH

1L

LIFT CONTACTOR

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