PT-150 PLUG-IN THERMAL RELAY WITH SNAP-ACTION BACK CONTACT *****************

Transcription

1 SERVICE MANUAL PT-150 PLUG-IN THERMAL RELAY WITH SNAP-ACTION BACK CONTACT ***************** This service specification provides information required for repair and adjustment of PT-150 thermal relays. I. GENERAL DESIGN The PT-150 thermal relay provides an adjustable time delay and is equipped with a back contact for checking the completion of its operating cycle. Referring to Figure 1, the thermal contact assembly consists of a driving element, heater element, front contact tip and back contact tip. The driving element consists of two bi-metallic strips fastened together end to end. The driver (d), which carries the heater coil, has the side of higher temperature coefficient of expansion facing to the left so that when the heater element is energized the assembly moves to the right and closes the front contact. The compensator (c) has the higher temperature coefficient side facing in the opposite direction and the lengths of these two strips (c and d) are so selected that with the relay deenergized the contact finger remains practically in a fixed position with the back contact closed regardless of the temperature in or around the relay. The snap-action of the back contact is obtained by means of a small permanent magnet located on the lower end of the back contact. This magnet retains a curved steel armature located at the lower end of the heater supporting member until the heat induced deflection of the bimetal strip overcomes its magnetic pull. At this point the back contact opens with a snap-action. Similar snap action also takes place, due to the magnetic pull, at the reclosure of the back contact. September, 1982 B-9/ UNION SWITCH & SIGNAL DIVISION AMERICAN STANDARD INC./ SWISSVALE, PA PRINTED IN USA

2 ffi UNION SWITCH & SIGNAL The relay is provided with two seals, one on the transparent cover and one on the rear screw holding the upper cover. As shipped from the factory the seals are in place but the seal on the rear screw of the upper cover is not crimped. Access to the Front contact adjustment screw is obtained by removing the upper cover which is held by two screws. The relays are for plug-in mounting and should be timed and installed in this position. The transparent cover should always be in place when making timing check. II. HEATER The heater coil may be operated from either an a-c or d-c source of power and consumes approximately 10 watts (13 watts for 5-12 sec. relay). ill. MECHANICAL INSPECTION The flexible connectors should be neatly dressed so that they will not touch other metallic parts of the relay. The silver contacts on the thermal element should touch the adjustable front and back contacts approximately in the center of the contact face, i.e., between the rivets and the end of the contact, and the contacts should line up squarely with each other. UPPER COYER (REMOVE TO MAKE FRONT CONTACT ADJUSTMENT) EXTERNAL.r-~FRONT '"'=' CONTACT ADJUSTMENT ~~I~ i::~~ O?IJ COMPENSATOR (C) i-..---shipping LOCK PERMANENT MAGNET CURVED STEEL ARMATURE 4578, p. 2 Figure 1

3 UNION SWITCH & SIGNAL It should be noted that the back contact spring rests against the adjusting screw with enough pressure to follow the movement of the screw when adjustments are being made. IMPORTANT: The bi-metallic thermal element must never be bent for adjustment. Bend only the heavy support members or the silver contacts. IV. ELECTRICAL TEST Testing apparatus as shown in Figure 2 will be found convenient for the electrical tests and adjustments of PT-150 relays. Two time intervals are to be taken: "Front contact time" and "Total operating time." "Front contact time" is the time from the instant energy is applied until the front contact closes. "Total operating time" is the time from the instant energy is applied until the back contact recloses (after the relay has made its front contact, has been deenergized, and its driver has cooled to return to its original position). These time intervals are shown in Table 1. BATTERY:- USE AT LEAST ONE MORE CELL OF STORAGE BATTERY THAN REQ.UIRED TO OBTAIN RATED VOLTAGE AUXILIARY RELAY , PN-150B OR 1000"" ON-11 LOW VOLTAGE D.C. AS REQ.UIRED FOR LAMPS USED. USE LOW WATTAGE LAMPS. FRONT CONTACT TIME INDICATOR LAMP. TOTAL OPERATING TIME INDICATOR LAMP. F PT-150 RELAY Figure , p. 3

4 ffi UNION SWITCH & SIGNAL To obtain these operating time intervals, proceed as follows: Close the knife switch 11 S 11, at the same time starting a stop watch, preferably one having two second hands. The "total time indicator lamp" will go out when the back contact opens. When the PT-150 front contact makes, the PN-150B relay will pick up and light the "front contact time indicator lamp". One hand of the stop watch should be stopped to record this time. The other hand should be stopped when the "total operating time indicator lamp" re-lights. After a test of the time interval has been made, it is necessary to wait at least eight (8) minutes (five minutes if cover is removed) before retesting in order to permit the relay to cool and assume normal position. An additional time interval must be measured to check the proper snap-action of the Back Contact. This time is shown in Table 1 and is measured as the time interval between closure of switch "S" and when "total time indication lamp" goes out. Back contact closure should take place with a snap or quick action when the heel contact approaches the back contact. It is not necessary that the armature snap against the permanent magnet stop-pin at the same time that the contact closes but it should move to the stop-pin within a few additional seconds. V. CONTACT ADJUSTMENTS Refer to Table 1. Assuming that the relay having an operating range of seconds front contact time and seconds total operating time is to be adjusted, proceed in accordance with the following sections. A similar procedure should be followed for relays of other ranges using values as given in the table. A. Back Contact Adjustment 1. With the heel spring and the back contact stop pulled away from the back contact, adjust the back contact spring so that the engaging surface of its contact tip is in a plane with the pole faces of the permanent magnet. Turn the back contact adjusting screw slowly until the back contact just touches, and set the lock nut against the bracket. 2. With the heel spring still away from the back contact, adjust the back contact stop to just touch the spring. 3. With the heel spring released, adjust its armature so that the back contact is compressed sufficiently to give an opening of approximately 0.002" at the back contact stop. Moving the heel spring by hand should exhibit a definite snap-open, snapclosed contact action. 4. In some cases it will be necessary to increase or decrease the back contact compression in order to meet the prescribed time to open the back contact. This should be done by adjusting the armature away from or toward the permanent magnet. This adjustment should be made by bending the straight portion of the armature. The curved portion normally should not have to be adjusted. 4578, p. 4

5 UNION SWITCH & SIGNAL m B. Front Contact Adjustment Insert a screw driver in the front contact adjusting terminal post (under the upper cover); with the back contact just open, adjust the front contact opening to be approximately inch. C. Adjustment and Check for Minimum Time Rating 1. Obtain front and back contact time, as explained in Section IV, at rated voltage as shown on the relay nameplate. If the front contact time is not 10 seconds (the minimum value as called for in the first column of the table), re-adjust the front_ contact opening until 10 seconds front contact time is obtained. This is very important and must be done accurately. 2. If the front contact time is correct but the time to open the back contact is too short and the total time is too long, bend the heavy supporting member for the heel spring to move it slightly towards the back contact. This will require adjusting the front contact toward the back contact in order to maintain the front contact time. Since repeated adjustments of this type may increase the back contact compression too much, a recheck of the Back contact adjustments in Section V-A should be made before testing the time intervals. If it is too much, the armature should be bent toward the permanent magnet. 3. If the front contact time is correct but the time to open the back contact is too long and the total time is too short, bend the heavy supporting member for the heel spring to move it slightly away from the back contact. This will require adjusting the front contact away from the back contact in order to maintain the front contact time. Since repeated adjustments of this type may decrease the back contact compression too much, a recheck of the Back contact adjustments in Section V-A should be made before testing the time intervals. If it is insufficient, the armature should be bent away from the permanent magnet. 4. Check front and total operating times and readjust until 10 seconds front contact time and 45 seconds total operating time are obtained. Next, bend the front stop for the back contact until it is about inch from the back contact spring with the relay deenergized. This is to limit the movement of back contact spring and prevent a possible short circuit between front and back contact should the back contact "freeze." Adjust and lock the front contact stop screw (see Figure 1) so that its tip is within inch from, but not touching, the adjusting bracket. This setting of the stop screw limits the minimum front contact time that can be obtained to slightly less than 10 seconds by making it impossible to further reduce the front contact opening. With minimum front contact time adjustment thus made, move the relay driver by hand until the back contact just opens. At that point note the front contact opening. It should be at least inch for all relays, regardless of time rating. When releasing the driver, note that the back contact has appreciable compression. 4578, p. 5

6 m UNION SWITCH & SIGNAL D. Adjustment and Check for Maximum Time Rating Recheck the front and total operating time at the minimum setting, then increase the front contact opening until the total operating time at rated voltage is 120 seconds (the maximum rated value shown in the table for the relay used as example). If it is less, increase the front contact opening until 120 seconds is obtained, but do not change the back contact adjustment. The back contact adjustment should not be disturbed after the minimum time adjustment has been made. TABLE NO.!. Time Limits or Values with Minimum Time Settings Rated Times in Seconds Actual Times in Seconds Front Contact Time Total Time To Open Back Contact To Close Front Contact Total Time E. Timing Tolerances If the relay has been adjusted to meet the requirements in Table 1 for actual times with minimum time settings, the rated maximum time settings should be within the limits specified below. In Table 1, the time values are subject to tolerances as follows: 1. The minimum front time should be adjusted to the time as indicated. 2. The minimum total time then should be within 3% of the time indicated. However, it should be noted here that it is usually not possible to take full advantage of this tolerance because of probable difficulty in obtaining the proper maximum total time. It is for this reason that the values listed under total time column of the actual time section of Table 1 should be followed as closely as possible. 3. The maximum front time should be within 10% of the time value indicated. 4. The maximum total time should be within 3% of the time value indicated. As an example of these tolerances, consider the 5-12 second front time and second total time relay. 4578, p. 6 The minimum front time should be five seconds.

7 UNION SWITCH & SIGNAL m The minimum total time should be between and seconds. However, if it is not held to between 24.5 and 25 seconds, as indicated in Table 1, there is a good possibility that difficulty will be encountered in obtaining the proper maximum total time. The maximum front time should be between 10.8 and 13.2 seconds and the maximum total time should be between and seconds. 5. Adjustment for Service After making the check under Sections D and E, the relay is ready for final time setting and may be adjusted within the time ranges specified to meet service requirements. To obtain a specific adjustment of front contact time or total time, adjust the front contact only by means of the external adjustment screw until the required time is obtained. VI. SHIPPING LOCK The PT-150 relay is equipped with a shipping lock which should be used to hold the moving element during shipment. In order to release the lock, back off the screw in the underside of the relay case until the screw is within 1/32" of the undersurface. Do not remove screw beyond this point, as the spring tension on screw will be insufficient to keep it from moving due to normal vibration. To apply lock to moving elements, turn screw in until the slotted pin properly engages the connector plate on the relay heel enough to sufficiently hold the moving. element during shipment; it may be necessary to tilt the relay to secure a proper alignment. The shipping lock must be disengaged only when relay is installed for service. 4578, p. 7

8 ,i:,. Ul -..J,CX>... I-CJ ~ ::,~1 7" EB c z 5 z ~ :j (') :I: 2> rjl c5 z )> r 7" 216 ~:~ ~zzz:~l SECTION Z-Z I f b ~ 1,-;~: ' t z =~---=--::_:j -= z f;:.,~ ~,~,~ t:1~~ tl~q (Jq. ~ I, I:=::! O 139 ~ 7L 16 ) , A 2 STYLE PT-150 THERMAL RELAY ~

9 UNION SWITCH & SIGNAL ffi Fig. 3- Style PT-150 Thermal Relay. Does not include Mounting Base Index Part Coil Rating Time Ranges Obtainable Volts Ohms with Front Contact Adjustment *Front Contact Time-Seconds **Total Operating Time-Seconds -A -Aa -Ab -Ac -Ad - N N N N N *Front Contact Time is the time from instant energy is applied to heater coil until front contact makes. **Total Operating or Back Contact Time is the time from instant energy is applied to heater coil until the contact recloses after the front contact has been made and some relay thus picked up has opened the heater circuit. Fig. & Index a -2b -2c -2d a -4b -4c -4d -5-6 Part M N N N N N J N I N N N N Ml04603 Ml83493 Description Frame Operating Unit Complete. Coil rating 10 volts, 7 ohms; seconds total operating time. For A Operating Unit Complete. Coil rating 8 volts, 6.4 ohms; seconds total operating time. For Aa Operating Unit Complete. Coil rating 10 volts, 10 ohms; seconds total operating time. For Ab Operating Unit Complete. Coil rating 12 volts, 14 ohms; seconds total operating time. For Ac Operating Unit Complete. Coil rating 12 volts, 10 ohms; seconds total operating time. For Ad Terminal Board. Thermal Contact for 2 Thermal Contact for 2a Thermal Contact for 2b. Thermal Contact for 2c Thermal Contact for 2d Binding Post Binding Post 4578, p. 9

10 UNION SWITCH & SIGNAL Fig. & Index Part Description Ml90681 M N N M M M Nut Nut Back Contact Front Contact Machine Screw, 6-40 x 1/2" fil. hd. brass (N. Pl.) Nut Nut Lock Adjusting Screw Machine Screw, 6-32 x 1/2" fil. hd. steel Contact Block Complete a -45b -45c -45d , p. 10 M J M J M N J M M M J M J M M J M J A M M M M M M ;.1805 J Contact Finger Contact Clamp Wedge Machine Screw, 6-32 x 7/8" fil hd. steel (Tin Pl.) Machine Screw, 8-32 x 7 /8" rd. hd. steel (Tin Pl.) Washer (Tin Pl.) Cover Cover Gasket Screw, 6-32 x 5/16" rd. hd. steel (Tin Pl.) Washer Handle Machine Screw, 8-32 x 3/8" fil. hd. steel (Tin Pl.) Lock Washer, 8 plain steel (Tin Pl.) Latch Rod Nut (Tin Pl.) Latch Dowel Pin Spring Screw Cap Screw, 1/4"-20 x 3/4" hex. hd. steel (Tin Pl.) Indexing Pin Screw Seal Seal Wire (Orders should specify length desired) Name Plate Screw, 4-40 x 3/16" rd. hd. steel (Tin Pl.) Indexing Plate for A (Not Shown) Indexing Plate for Aa (Not Shown) Indexing Plate for Ab (Not Shown) Indexing Plate for Ac (Not Shown) Indexing Plate for Ad (Not Shown) Screw, 6-32 x 1-1/4" fil. hd. steel (Tin Pl.) For attaching Indexing Plate to Mounting Base (Not Shown) Tag

11 ... UNION SWITCH & SIGNAL Mounting Base with solderless type receptacles for PT-150 Thermal Plug-In Relay Fig. & Index Part Description 4-A N J J J M M J J J * J * J * J * J * J N J " 1_ -,~ r- 1 ~--~-- Mounting Base Complete with solderless type receptacles for PT-150 Thermal Plug-In Relay Mounting Base Only Clamping Plate. Screw, 6-32 x 5/8" fil. hd. steel mach. (Tin Pl.). Strike Nut. Tag. Screw, 4-40 x 3/16" rd. hd. self-tapping (Tin Pl.). Contact Receptacle (solderless type). Screw, 1/4"-20 x 1-1/4 11 rd. hd. rp.ach. (Tin Pl.) Washer. Lock Washer, 1/4" steel (Tin Pl.) Washer, 1/4 11 steel plate (Tin Pl.) Nut, 1/4 11 steel hex. (Tin. Pl.) Meter Test Plug. Insulated Test Plug *For attaching Mounting Base to Rack (Not Shown) 5" 716 APPLY REC.EPTAClE SPR.INCS WITL4 LOC.1-:INC. SlO( OOWN A --fl -. MOUNTING BASE Figure , p. 11

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