Type CO-4 Step-Time Overcurrent Relay For Class 1E ......41-106.1B 4 CO-4 Step-Time Overcurrent Relay The maximum time setting of the timer is three sec-onds (180 cycles) and the minimum

41-106.1B CO-4 Step-TimeOvercurrent Relay

bridge two stationary contacts, competing the trip cir-cuit. Also during this operation two fingers on thearmature deflect a spring located on the front of theswitch, which allows the operation indicator target todrop.

The front spring, in addition to holding the target, pro-vides restraint for the armature and thus controls thepickup value of the switch.

2.3 INDICATING INSTANTANEOUS TRIP UNIT (IIT)

The instantaneous trip unit is a small ac operatedclapper type device. A magnetic armature, to whichleaf-spring mounted contacts are attached, isattracted to the magnetic core upon energization ofthe switch. When the switch closes, the moving con-tacts bridge two stationary contacts completing thetrip circuit. Also, during the operation, two fingers onthe armature deflect a spring located on the front ofthe switch which allows the operation indicator targetto drop.

A core screw accessible from the top of the switchand taps on the coil provides the adjustable pickuprange.

2.4 TIMER (T)

The timer may be either an electromechanical orsolid-state type. The electromechanical timer is asmall synchronous motor which operates from the cur-rent circuit through a saturating transformer, anddrives a moving contact arm through a gear train. Thecontact on the moving arm is a cylindrical silversleeve, loosely fitted on the moving arm. In makingcontact, this sleeve strikes two vertically projectingstationary butt contacts to bridge the gap betweenthem. The loose fit of the sleeve permits a positivealignment in bridging these contacts, and, therefore,correct contact action is not greatly dependent on theiradjustment. The stationary contacts are mounted on amolded insulating block which is adjustable around asemicircular calibrated guide. The maximum time set-ting of the timer is three seconds.

The synchronous motor has a floating rotor which isin mesh with the gear train only when energized. Therotor falls out instantly when the motor is de-ener-gized, allowing a spring to reset the moving arm.

The solid-state timer consists of a printed circuitboard with an output telephone relay, a rectifier, twooperational amplifiers and several associated com-ponents.

2.5 INSTANTANEOUS TRIP UNIT (IT)

The instantaneous Trip unit is a small ac operatedclapper type device. A magnetic armature, to whichleaf-spring mounted contacts are attached, isattracted to the magnetic core upon energization ofthe switch. When the switch closes, the moving con-tacts bridge two stationary contacts completing thetimer circuit.

A core screw accessible from the top of the switchand taps on the coil provides the adjustable pickuprange.

The IT contacts are connected in series with thetimer to allow an adjustable time delay after the ITpicks up.

3.0 CHARACTERISTICS

The typical current ranges of the unit of the typeCO-4 relay are as follows:

CO-5 type long time overcurrent unit 4 to 12 ampereswith taps at 4-5-6-7-8-10 and 12 amperes. The tapvalue is the minimum current required to just closethe relay contacts.

IIT instantaneous unit has an adjustable range of 6 to144 amperes.

The IT instantaneous unit has an adjustable range of6 to 144 amperes. However, the usable range of thedevice is 10 to 100 amperes. This range restriction isdue to the timer (T) which is activated by the ITdevice. The range of the timer is 10 to 100 amperesand 0.5 to 3 seconds for the electromechanical unitor 0.25 to 3 seconds for the solid-state unit.

The typical operating curves of the CO-5 unit areshown by Fig 4. The time dial indicates starting posi-tion of the moving contact over a 270° range.Indexes from 1 (minimum time) to 11 (maximumtime).

The typical band curves of the overall operating char-acteristic of the type CO-4 relay are shown by Fig. 5.

3.1 TRIP CIRCUIT

All tripping contacts are connected in parallel whichallows tripping by the CO-5 long time unit. IT plustime delay or IIT instantaneously, depending on therelative unit settings and current magnitude.

The main contacts will close 30 amperes at 250 volts

2

41-106.1BCO-4 Step-TimeOvercurrent Relay

dc and the seal-in contacts of the indicating contac-tor switch will carry this current long enough to trip acircuit breaker.

The indicating instantaneous trip contacts will close30 amperes at 250 volts dc, and will carry this cur-rent long enough to trip a breaker.

3.2 TRIP CIRCUIT CONSTANTS

4.0 SETTINGS

The settings are made to obtain an operating char-acteristic similar to that indicated by the examplecurve of figure 5.

4.1 CO UNIT

The overcurrent unit settings can be defined eitherby tap setting and time dial position or by tap settingand a specific time of operation at some current mul-tiple of the tap setting (e.g., 4 tap setting, 2 time dialposition or 4 tap setting, 6.0 seconds at 4 times tapvalue current).

To provide selective circuit breaker operation, a min-imum coordinating time of 0.3 seconds plus circuitbeaker time is recommended between the relaybeing set and the relays with which coordination isto be effected.

The connector screw on the terminal plate abovethe time dial makes connections to various turns onthe operating coil. By placing this screw in the vari-ous terminal plate holes, the relay will respond tomultiples of tap value currents in accordance withthe various typical time-current curves.

CAUTION!Since the tap block connector screw carriesoperating current, be sure the screw is turnedtight.

In order to avoid opening current transformer circuitswhen changing taps under load, the relay must befirst removed from the case. Chassis operatingshorting switches on the case will short the second-ary of the current transformer. The taps should thenbe changed with the relay outside of the case andthen re-inserted into the case.

4.1.1 Instantaneous Reclosing

The factory adjustment of the CO unit contact pro-vides a contact follow. When instantaneous circuitbreaker reclosing will be initiated upon the closure ofthe CO contact, this contact follow must be elimi-nated by loosening the stationary contact mountingscrew, removing the contact plate and then replac-ing the plate with the bent end resting against thecontact spring. With this change and the contactmounting screw tightened, the stationary contact willrest solidly against its backstop.

4.1.2 Indicating Contactor Switch (ICS)

There are no settings to make on the indicating con-tactor switch (ICS).

4.2 INDICATING INSTANTANEOUS TRIP (IIT)

The proper tap must be selected and the core screwmust be adjusted to the value of pick-up currentdesired.

The nameplate data will furnish the actual currentrange that may be obtained from the IIT unit. It isrecommended that the IIT be set on the higher tapwhere there is a choice of tap settings. For example,for a 20 ampere setting use the 20 to 50 tap ratherthan the 6 to 20 tap.

4.3 INSTANTANEOUS TRIP UNIT (IT)

The proper tap must be selected and the core screwmust be adjusted to the value of pick-up currentdesired.

The nameplate data will furnish the actual currentrange that may be obtained from the IT unit. It is rec-ommended where there is a choice of tap settingsthat the IT unit be set on the higher tap setting. Forexample, for a 20 ampere setting use the 20 to 50tap rather than the 6 to 20 tap.

4.3.1 Timer (T)

The operating time of the electromechanical timer iscontrolled by a molded insulating block, on whichthe stationary contacts are mounted. These areadjustable around a semi-circular calibrated guide.

Indicating Contactor Switch Coil

Ampere Pick-up

Ohms dcResistance

0.21.02.0

8.50.370.10

3


The maximum time setting of the timer is three sec-onds (180 cycles) and the minimum time setting ofthe timer is 0.5 seconds (30 cycles). Its settingshould be 70 cycles or more to achieve a seismic fra-gility greater than 5.7 g ZPA.

The solid-state timer uses a trimpot P1 which con-trols the time delay from 0.25 to 3.0 seconds. Thisrange is marked on the PC board. (See figure 6) Thetime delay is proportional to the time constant pro-duced by P1, R7, C2 and C3 as shown in figure 7.The first op-amp is used as a voltage follower andthe second one is used as a voltage level detector.As the voltage across the capacitor C2 exceeds thevoltage level at pin 6 of IC2, the output telephonerelay picks up to close the T contacts.

5.0 INSTALLATION

The relay should be mounted on switchboard panelsor their equivalent in a location free from dirt, mois-ture, excessive vibration and heat. Mount the relayvertically by means of the four mounting holes on theflange for the semi-flush type FT case. The mountingscrews may be utilized for grounding the relay. Exter-nal toothed washers are provided for use in the loca-tions shown on the outline and drilling plan tofacilitate making a good electrical connectionbetween the relay case, its mounting screws and therelay panel. Ground wires should be affixed to themounting screws as required for poorly grounded orinsulating panels. Other electrical connections maybe made directly to the terminals by means of screwsfor steel panel mounting.

For detail information on the FT case refer to IL41-076 for semi-flush mounting.

6.0 ADJUSTMENTS ANDMAINTENANCE

Proper adjustments have been made at the factory.Upon receipt of the relay no customer adjustments,other than those covered under “SETTINGS” shouldbe required.

6.1 PERFORMANCE CHECK

The following check is recommended to verify thatthe relay is in proper working order.

6.1.1 CO Unit

1. Contact

The index mark on the movement frame will coincidewith the “0” mark on the time dial when the stationarycontact has moved through approximately one-half ofits normal deflection. Therefore, with the stationarycontact resting against the backstop, the index markis offset to the right of the “0” mark by approximately.020”. The placement of the various time dial posi-tions in line with the index mark will give operatingtimes as shown on the respective timecurrent curves.

2. Minimum Trip Current

Set the time dial to position 6. Alternately apply tapvalue current plus 3% and tap value current minus3%. The moving contact should leave the backstopat tap value current plus 3% and should return to thebackstop at tap value current minus 3%.

3. Time Curve

Table 1 shows the time curve calibration points. Withthe time dial set to the indicated position, apply thecurrents specified by Table 1 and measure the oper-ating time of the relay. The operating times shouldequal those of Table 1 plus or minus 5%IndicatingInstantaneous Trip (IIT).

The core screw which is adjustable from the top ofthe trip unit and the tap located on the top of the IITdetermines the pickup value. The trip unit has a nom-inal ratio of adjustment of 1 to 24.

Apply sufficient current to operate the IIT. The opera-tion indicator target should drop freely.

4. Indicating Contactor Switch (ICS)

Close the main relay contacts and pass sufficient dccurrent through the trip current to close the contactsof the ICS. This value of current should not begreater than the particular ICS nameplate rating. Theindicator target should drop freely.

Repeat above except pass 85% of ICS nameplaterating current. Contacts should not pickup and targetshould not drop.

5. Instantaneous Trip Unit (IT)

The core screw which is adjustable from the top ofthe trip unit and the tap located on the side of the ITdetermines the pickup value. The unit has a nominalratio of adjustment of 1 to 24 but its range is limitedfrom 10 amperes to 100 amperes.

4


Apply sufficient current to operate the IT.

6. Timer (T)

When checking the electromechanical synchronoustimer, complete the transformer circuit by a jumperaround the contacts of the IT unit. Test the motor at10 amperes (or the current indicated by the mini-mum possible setting of the IT unit) through the cur-rent circuit which includes the auxiliary transformerprimary. This is the minimum current at which thetimer will run in synchronism.

With the solid-state timer, it is not necessary tojumper around the IT contacts. Energize the IT cir-cuit at 150% of the IT setting to check the timer set-ting. The time delay of the solid-state timer isadjusted by a trimpot P1. A small arrow on the trim-pot indicates the setting position which is marked onthe PC board. The timer is factory calibrated and setfor a time delay of 2.5 seconds.

7.0 ROUTINE MAINTENANCE

All relays should be inspected periodically. Theyshould receive a “Performance Check” at least onceevery year or at such other time intervals as may bedictated by experience to be suitable to the particu-lar application. A minimum suggested check on therelay system is to close the contacts manually sothat the breaker trips the target drops. Then releasethe contacts and observe that the reset is smoothand positive.

If an additional time check is desired, pass test cur-rent through the relay check the time of operation. Itis preferable to make this at several times pick-upcurrent at an expected operating point for the partic-ular application.

All contacts should be checked and cleaned if nec-essary. A contact burnisher #182A836H01 is recom-mended for this purpose. The use of abrasivematerial for cleaning contacts is not recommended,because of the danger of embedding small particlesin the face of the soft silver and thus impairing thecontact.

8.0 CALIBRATION

Us the following procedure for calibrating the relay ifthe relay has been taken apart for repairs or the

adjustments disturbed. This procedure should notbe used until it is apparent that the relay is not inproper working order, (See “Performance Check”,page 4).

NOTE: A spring shield covers the reset springon the CO unit. To remove the springshield, requires that the damping mag-net be removed first. The screw con-nection holding the lead to the movingcontact should be removed next. Thesecond screw holding the moving con-tact assembly should then be loosenedNOT removed. CAUTION: this screwterminates into a nut held captivebeneath the molded block. If the screwis removed, difficulty will be experi-enced in the re-assembly of the movingcontact assembly. Slide the springshield outward and remove from relay.Tighten the screw holding the movingcontact assembly to the molded block.

8.1 CO UNIT

1. Contacts

The index mark on the movement frame willcoincide with the “0” mark on the time dial whenthe stationary contact has moved throughapproximately one-half of its normal deflection.Therefore, with the stationary contact restingagainst the backstop, the index mark is offset tothe right of the “0” mark by approximately .020”.The placement of the various time dial positionsin line with the index mark will give operatingtimes as shown on the respective time-currentcurves.

2. Minimum Trip Current

The adjustment of the spring tension in settingthe minimum trip current value of the relay ismost conveniently made with the damping mag-net removed.

With the time dial set on “0”, wind up the spiralspring by means of the spring adjuster untilapproximately 6-3/4 convolutions show.

The spiral can be adjusted with the spring shieldin place as follows. One slot of the springadjuster will be available for a screwdriver in onewindow of the front barrier of the spring shield.By adjusting this slot until a barrier of the springshield prevents further adjustment, a second

5


slot of the spring adjuster will appear in the win-dow on the other side of the spring shield barrier.Adjusting the second slot in a similar manner willreveal a third slot in the opposite window of thespring shield.

Set the relay on the minimum tap setting, thetime dial to position 6.

Adjust the control spring tension so that the mov-ing contact will leave the backstop at tap valuecurrent +1.0% and will return to the backstop attap value current -1.0%.

3. Time Curve Calibration

Install the permanent magnet.

Apply the indicated current per Table 1 for per-manent magnet adjustment and measure theoperating time. Adjust the permanent magnetkeeper until the operating time corresponds tothe value of Table 1.

Apply the indicated current per Table 1 for theelectromagnet plug adjustment and measure theoperating time. Adjust the proper plug until theoperating time corresponds to the value in Table1. (Withdrawing the left-hand plug, front view,increases the operating time and withdrawing theright-hand plug, front view, decreases the operat-ing time.) In adjusting the plugs, one plug shouldbe screwed in completely and the other plug runin or out until the proper operating time has beenobtained.

Recheck the permanent magnet adjustment. Ifthe operating time for this calibration point haschanged, readjust the permanent magnet andthen recheck the plug adjustment.

8.2 INDICATING CONTACTOR SWITCH (ICS)

Initially adjust unit on the pedestal so that armaturefingers do not touch the yoke in the reset position.(Viewed from top of switch between cover andframe.) This can be done by loosening the mountingscrew in the molded pedestal and moving the ICS inthe downward position.

a) Contact Wipe – Adjust the stationary contact sothat both stationary contacts make with the mov-ing contacts simultaneously and wipe 1/64” to3/64” when the armature is against the core.

b) Target – Manually raise the moving contacts andcheck to see that the target drops at the sametime as the contacts make or 1/16” ahead. Thecover may be removed and the tab holding the

target reformed slightly if necessary. However,care should be exercised so that the target willnot drop with a slight jar.

If the pickup is low, the front cover must be removedand the leaf spring bent outward equally.

8.3 INDICATING INSTANTANEOUS TRIP (IIT)

Initially adjust unit on the pedestal so that armaturefingers do not touch the yoke in the reset position.(Viewed from top of switch between cover andframe.) This can be done by loosening the mountingscrew in the molded pedestal and moving the IIT inthe downward position.

a) Contact Wipe – Adjust the stationary contacts sothat both stationary contacts make with the mov-ing contacts simultaneously and wipe 1/64” to3/64” when the armature is against the core. Thiscan be accomplished by inserting a .0125 thick-ness gauge between the armature and core andadjusting the stationary contacts until they justtouch the moving contacts.

b) Target – Manually raise the moving contacts andcheck to see that the target drops at the sametime as the contacts make. The cover may beremoved and the tab holding the target reformedslightly if necessary. However, care should beexercised so that the target will not drop with aslight jar.

c) Pickup – Place tap screw in the 6 to 20 tap andturn the core screw all the way in. Contactsshould pickup at less than 6.0 amps, but notlower than 5.1 amperes. If pickup is above thisrange it may be reduced by using a tweezer orsimilar tool and squeezing each leaf springapproximately equally by applying the tweezerbetween the leaf spring and the front surface ofthe cover at the bottom of the lower window. Ifthe pickup is below this range it may beincreased by removing the front cover and bend-ing the leaf springs outward equally. An approxi-mate adjustment would be where the end of theleaf spring is in line with the edge of the moldedcover.

The desired pickup is obtained by setting the tap screw in the proper range and adjusting the core screw.

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8.4 INSTANTANEOUS TRIP (IT)

Initially adjust unit on the pedestal so that armaturefingers do not touch the yoke in the reset position.(Viewed from top of switch between cover andframe). This can be done by loosening the mountingscrew in the molded pedestal and moving the IT inthe downward position.

a) Contact Wipe – Adjust the stationary contactsso that both stationary contacts make with themoving contacts simultaneously and wipe 1/64”when the armature is against the core.

This can be accomplished by inserting a .0125” thickness gauge between the armature and core and adjusting the stationary contacts until they just touch the moving contacts.

b) Pickup – Place tap screw in the 6 to 20 tap andturn the core screw all the way in. Contactsshould pickup at less than 6.0 amps, but notlower than 5.1 amperes. If pickup is above thisrange it may be reduced by using a tweezer orsimilar tool and squeezing each leaf springapproximately equal by applying the tweezerbetween the leaf spring and the front surface ofthe cover at the bottom of the lower window. Ifthe pickup is below this range it may beincreased by removing the front cover andbending the leaf springs outward equally. Anapproximate adjustment would be where theend of the leaf spring is in line with the edge ofthe molded cover.

The desired pickup is obtained by setting the tap screw in the proper range and adjusting the core screw.

8.5 TIMER (T)

Complete the transformer circuit by a jumper aroundthe contacts of the IT unit. Energize the timer trans-former primary with 10 amperes and note the time ofoperation of the timer with a setting of 150 cycles.The operating time should be within ±5% of indi-cated value for the electromechanical timer.

For the solid-state timer, do not jumper around theIT contacts. Apply 150% of t he minimum pickupcurrent for the IT and note the time of operation ofthe timer with a setting of 2.5 seconds. The operat-ing time should be within ±5% of indicated value . Iftime is not within limits, the time for a given P1 set-ting can be increased by adjusting multi-turn pot P2

in the clockwise direction. Conversely, the time canbe decreased by counterclockwise rotation of P2.

9.0 RENEWAL PARTSRepair work can be done most satisfactorily at thefactory. However, interchangeable parts can be fur-nished to customers who are equipped for doingrepair work. When ordering parts, always give thecomplete nameplate data.

.

Table 1: Time Curve Calibration Data

60 Hertz

PERMANENT MAGNET ADJUSTMENT

TimeDial

Position

Current(Multiples ofTap Value)

OperatingTime

Seconds

6 2 37.8

ELECTROMAGNET PLUGS

Current(Multiples ofTap Value)

OperatingTime

Seconds

10 14.3

ENERGY REQUIREMENTS

Timer

The burden of the timer and auxiliary trans-former at 5 amperes 60 Hertz is as follows:

IT contact open 0.7 VA at 80° lag.(both EM and SS)

IT contact close 0.6 VA at 65° lag.(Electromechanical)

IT contact close 1.7 VA at 50° lag.(Solid-state)

7

41-106.1B

8

CO-4 Step-TimeOvercurrent Relay

INSTANTANEOUS TRIP UNIT (IT) MEASURED SEPARATELY

TYPEOF

UNIT

RANGESAVAILABLEWITH CORE

ADJUSTMENTTAP

SETTINGMINIMUMPICKUP

BURDEN

CONT.RATINGAMPS

1 SECONDRATINGAMPS

AT PICKUP3 TIMESPICKUP

OHMS10 TIMESPICKUP

20 TIMESPICKUPR XL Z

6-1446-20

20-5050-144

6-2020-50

50-144

62050

.144

.023

.009

.108

.012

.002

.180

.026

.009

.180

.026

.009

.180

.026

.009

.180

.026

.009

61320

100230370

CO-5 LONG TIME UNIT

AMPERERANGE TAP

CONTINUOUS ONE SECOND

POWERFACTOR

ANGEL†

† Degrees current lags voltage at tap value current.

ATTAP VALUECURRENT

VOLT AMPERES‡

‡ Voltages taken with high resistance voltmeter, not less than 2000 ohms per volt.

AT 20 TIMESTAP VALUECURRENT

RATING(AMPERES)

RATING††

(AMPERES)

†† Thermal capacities for short times other than one second may be calculated on the basis of time being inversely proportional square of the current.



4/12

45678

1012

1618.819.320.822.52528

460460460460460460460

65636159565347

4.004.154.324.354.404.604.92

22.423.725.326.427.830.135.6

126143162183204247288

376450531611699880

1056


Figure 1. Type CO-4 Relay with Electromechanical Timer, without Case

9


Figure 2. Type CO-4 Relay with Solid-state Timer, without Case

10


3529A34Sub 1

Figure 3. Internal Schematic of the Type CO-4 Relay in Type FT-21 Case

11


619510Sub 1

Figure 4. Typical Time Curves for Overcurrent Unit

12


1458C94Sub 2

Figure 5. Typical Current Time Curve Bands for Type CO-4 Relay

13


3529A15Sub 2

Figure 6. Component Location - Timer Module

14


1484B34Sub 1

Figure 7. Internal Schematic - Timer Module

15

Documents

Type CO-4 Step-Time Overcurrent Relay For Class 1E ......41-106.1B 4 CO-4 Step-Time Overcurrent Relay The maximum time setting of the timer is three sec-onds (180 cycles) and the minimum