Instructions for Ampgard®

Isolating Switches Rated3500, 5000 or 7200 Voltsand Their Auxiliary Switches

I.L. 17116C

tor which is mounted in the Ampgard starter. In the openposition, the three fuse jaw fingers are grounded.

Arc resistant and flame retarding insulating barriersare mounted between phases and also between the twooutside poles and the isolating switch end plates. Theswitch can be easily removed from the Ampgardstructure.

Although Ampgard isolating switches are alwaysused enclosed they are identified by their open ampererating. See Table I.

APPLICATIONAn Ampgard isolating switch is used in an Ampgard

motor controller with either an air-break or a vacuum-break medium-voltage contactor and current-limitingfuses designed for motor branch circuits. This isolatingswitch is a non-load break device. It must neverclose or interrupt a power load. However, it does havea very limited capacity for interrupting the single-phasecontrol transformer exciting current or a load which doesnot exceed the values shown in Table I.

INSTALLATIONThis industrial type control is designed to be installed,

operated, and maintained by adequately trained work-men. These instructions do not cover all details, varia-tions, or combinations of the equipment, its storage,delivery, installation, check-out, safe operation, or main-tenance. Care must be exercised to comply with local,state, and national regulations, as well as safety prac-tices, for this class of equipment.

The assembled isolating switch slides into the Amp-gard structure on two rails. The isolating switch shouldbe positioned so that all doors close properly, themounting holes line up, and the mechanical interlockto the contactor is in the proper location. The switchis bolted in place with two 5/16’-18 x 1” socket head capscrews located above and to each side of the simulatedgrills. (See Figure 2.)

Fig. 1 Ampgard Starters

THE SWITCHEach Ampgard isolating switch is a medium-voltage,

three-pole, manually operated device. It consists of anoperating mechanism and a sliding tray or crossbarmounted between two steel end plates. The sliding trayis molded insulating material and carries three sets offuse jaw finger assemblies. One end of the fuse jawfinger assembly grips the upper ferrule of the powerfuse while the other end engages the line stab connec-

TABLE I — ISOLATING SWITCH RATINGSMaximum Carry Current Maximum Make and Break Capacity Reference

FigureCatalog

DesignationMaximum

Voltage 3501 to Maximum VACOpen Enclosed 601 to 3500 VAC

935 LFR250 LFR272 LFR272 LFR472 LFS472 LFM772 LFM8

3500 VAC5000 VAC7200 VAC7200 VAC7200 VAC7200 VAC7200 VAC

200 Amp200 Amp200 Amp400 Amp400 Amp700 Amp800 Amp

180 Amp180 Amp180 Amp360 Amp360 Amp630 Amp720 Amp

750 VA750 VA750 VA750 VA750 VA750 VA750 VA

10600 VA600 VA600 VA600 VA600 VA600 VA

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AMPGARD ISOLATING SWITCH I.L. 17116C

SWITCH OPERATIONAn Ampgard starter is shipped with the isolating

switch in the ON position (Figure 2, View A). The isolat-ing switch handle is operated by moving it through avertical arc from the ON to the OFF position. From theOFF position, it can be rotated 90° counterclockwiseto the HORIZONTAL position, the door-open position.

In both the ON and OFF positions, a portion of thehandle housing extends over the door to the mediumvoltage compartment, preventing this door from beingopened. To open this door, the handle must be movedto the HORIZONTAL position.

With the handle in the OFF position, up to three pad-locks can be used to lock the switch, preventing thehandle from being moved to either the ON or theHORIZONTAL position. This locked position preventsboth unauthorized entry into the medium-voltage com-partment and accidental closing of the isolating switchwhile maintenance work is being done. From theHORIZONTAL position, the handle cannot be movedto the ON position without first moving to the OFFposition.

voltage compartment can be opened. As soon as thedoor opens, a mechanical interlock becomes effective.It is designed to prevent the user from accidentally oper-ating the isolating switch handle and closing the starteron to the line with the door open.

This interlock is a spring-loaded plunger located justbelow the handle housing (Figure 2, View D). This pre-vents the handle from being accidentally returned to theOFF position. This interlock may be deliberatelybypassed by depressing the plunger with a screwdriverso that the handle can be moved to the OFF positionto observe the operation of the isolating switch duringinstallation or maintenance. To do this, it is necessaryto deliberately bypass the interlock. The handle mustbe returned to the HORIZONTAL position by againdepressing the interlock plunger before the door canbe closed. The operator must be aware of what he isdoing and take appropriate safety precautions.

Contactor-to-lsolating-Switch Mechanical Inter-lock. Each Ampgard isolating switch functions only asa disconnect; it must never close, or interrupt a powerload. To prevent this in the case of a Type 72LFR4 switchused with a Type LF50H430 contactor (Figure 3), theinterference lever roller (30), on the contactor isengaged by a cam (24) on the isolating switch. If thecontactor is closed, the isolating switch cannot bemoved either from the OFF to the ON, or from the ONto the OFF positions. This is a positive interlock, it can-not be bypassed without disassembly of the interlock-ing parts.

Where a Type 72LFS4 isolating switch is used witha Type SJS contactor, this mechanical interlocking is

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The operating handle has three distinct positions.In the ON position (A), the isolating switch is closed,the door is interlocked shut, and the starter may beenergized.In the OFF position (B), the isolating switch is open,the door is interlocked shut, and the starter is de-energized and grounded.With the handle rotated 90° counterclockwise (C) to theHORIZONTAL position (D), the isolating switch is open,the starter is de-energized and grounded, and the doormay be opened.

Fig. 2 Operating Handle Positions

MECHANICAL INTERLOCKSBefore putting the isolating switch into service,

become familiar with the mechanical interlocks.Door Interlock. With the isolating switch handle in

the HORIZONTAL position, the door to the medium-Fig. 3 Type 72LFR4 Isolating Switch and Type

LF50H430 Contactor

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AMPGARD ISOLATING SWITCHES I.L. 17116C

accomplished with the mechanism shown in Figures4 and 5. The linkage as shown in Figure 4 insures thatthe isolating switch remains in its position while the con-tactor is closed and also lowers the far end of the inter-lock arm to keep the contactor blocked open wheneverthe isolating switch is being opened or closed, thuskeeping the isolating switch from making or breakingthe current controlled by the contactor. This same link-age becomes neutral after the isolating switch is fullyOPEN or CLOSED as shown in Figure 5 and then actsto prevent the isolation switch from being opened orclosed when the contactor is closed. If the clevis andclevis bolt are not in place, a counterweighted interlockarm prevents the contactor from being closed electri-cally. Other types of Ampgard isolating switches usedifferent mechanism parts to achieve the same end. DONOT DISTURB THE FACTORY ADJUSTMENTS OFTHESE INTERLOCKS!

Line Stab Insulating Shutter. When an Ampgardisolating switch is installed, both a shutter and a rearline stab barrier are in place in the starter structure andare intended to prevent accidental access to the linebus. As the isolating switch is opened, the crossbarmechanism (Figure 7) or molded cam surface of thesliding tray mechanically drives the insulating shutterclosed across the three line stab openings in the rearbarrier. As the shutter closes the openings, green andwhite striped labels are uncovered to visually indicatethat the shutter is closed. With the isolating switch inthe fully open position, the fuse jaw finger assembliesand the line side of the main fuses are connected tothe ground bar.

As a final precaution before touching any of the elec-trical parts of the starter, visually check to make cer-tain that the shutter is closed, the green and whitestriped labels are visible, the grounding fingers are incontact with the ground bar, and the tips of the fusefingers are visible.

When a 200 ampere or 400 ampere isolating switchis removed from the starter structure, a latch lever (32,Figure 6) on the shutter assembly is activated. It isdesigned to hold the insulating shutter closed. Thislatch may be deliberately bypassed and the shutter

Fig. 4 Type 72LFS4 Isolating Switch Interlocked Closedwith Contactor Closed

Fig. 6 Shutter Operating MechanismFig. 5 Type 72LFS4 Isolating Switch with ContactorOpen, Interlock Neutral

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AMPGARD ISOLATING SWITCHES

Instructions for Replacing an Auxiliary SwitchAssembly on Medium-Voltage Isolation Switches

I.L. 17116C

THE AUXILIARY SWITCHThe auxiliary switch kit, part number 843D946G04,

consisting of an auxiliary switch mounted to a new stylespring plate and leads, is designed for adding or replac-ing auxiliary switches used with Type LFR, LFS andLFM Isolation Switches. The kit includes a switch mech-anism with an inductive-load rating of 16 amperes atnot more than 125 VAC or 12 amperes at not more than250 VAC. The kit may be applied to any Type LFR, LFSor LFM Isolation Switch.

men. These instructions do not cover all details, varia-tions, or combinations of the equipment, its storage,delivery, installation, check out, safe operation, or main-tenance. Care must be exercised to comply with local,state, and national regulations, as well as safety prac-tices, for this class of equipment.

ASSEMBLY INSTRUCTIONSAssemble as shown in Figure 13. Carefully remove

old switch or old style spring plate from rear of doorinterlock spring housing. Do not remove the spring ordoor interlock pin. Discard the old spring plate. Usespring plate mounting hardware to mount the auxiliaryswitch assembly (switch mechanism mounted to newstyle spring plate) to the spring housing.

INSTALLATIONThis industrial type control is designed to be installed,

operated, and maintained by adequately trained work-

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AUXILIARY SWITCH ASS’Y SPRING HOUSING BOSS TO WHICH SPRING PLATE IS MOUNTED

Fig. 13 Front View of Auxiliary Switch Installed

Effective 11/87Supersedes 17116B (6/87)

16-200-21 (10/79)16-200-22 (2/80)16-200-23 (4/75)16-200-28A (10/85)

Westinghouse Electric CorporationConstruction Equipment Division

Asheville, N.C., U.S.A. 28813

Printed in USA

AMPGARD ISOLATING SWITCHES I.L. 17116C

Welded Jaws or Contacts

In the unlikely event that either the isolating switchfuse jaws or the contactor contacts should weld closed,or if an event should occur such that the isolating switchhandle cannot be moved from the ON to the OFFposition, provision has been made so that the door tothe medium-voltage compartment can be opened in anemergency. The door can be opened by using the fol-lowing procedure:1. Make sure that the main incoming power line is

de-energized, to avoid a hazardous situation whenthe door is opened.

2. Remove the four screws holding the rectangular han-dle housing of the isolating switch to the front cast-ing. (See Figure 2.)

3. Disconnect the leads between the isolating switchauxiliary switch and the control power transformer.

4. The complete handle housing can now be pushedup far enough to provide clearance for opening thedoor and any maintenance carried out.

iliw -

Fig. 7 Crossbar Mechanism of 700 AmpereIsolating Switch

moved to the open position. CAUTION! Under theseconditions the exposed line terminal stabs of thestarter may be energized at line potential.

When the isolating switch is replaced in the structure,the latch member is automatically released to allow theshutter to operate normally.

When a 700 ampere or 800 ampere isolating switchis removed from the starter enclosure, the shutter andshutter operating mechanism come along with theswitch, leaving the line terminal stabs exposed. There-fore, open the feeder disconnect means beforeremoving a Type 72LFM7 or 72LFM8 isolating switchfrom the structure. Do not work within a starterenclosure with exposed line terminal stabs that areenergized!

AUXILIARY SWITCHAn auxiliary switch (Kit Part Number is 843D946G04)

may be installed behind the operating handle housingand used to disconnect the load of a control transformer,space heaters, or other auxiliary circuits, particularlywhen the load exceeds the Make-Break Capacity of theisolating switch shown in Table I. The auxiliary switchhas an inductive load rating of 16 amperes at not greaterthan 125 VAC or 12 amperes at not greater than 250VAC. See back page for installation instructions.

MAINTENANCEThis industrial type control is designed to be installed,

operated, and maintained by adequately trained work-men. These instructions do not cover all details, varia-tions, or combinations of the equipment, its storage,delivery, installation, check-out, safe operation, or main-tenance. Care must be exercised to comply with local,state, and national regulations, as well as safety prac-tices, for this class of equipment.

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LubricationPeriodically (approximately every 100 operations),

apply a light coating of Dow Corning DC-4 high tem-perature silicone grease (or equivalent) to the tips ofthe fuse jaw fingers where they engage the line termi-nal stabs. Also clean and lubricate the tray guide rails(Figure 6).

Fig. 8 Type 72LFS4, 400 Ampere Switch

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AMPGARD ISOLATING SWITCHES I.L. 17116C

Fig. 11 Type 72LFR4, 400 Ampere Isolating SwitchFig. 9 Type 35LFR2, 200 Ampere Switch

Fig. 12 Type 72LFM7, 700 Ampere Switch, 7200 VoltsFig. 10 Type 50LFR2, 200 Ampere Switch

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