Manual / Guide · 1961
Technical Bulletin 961-537: Relays Class B and Class C (Type 57-A and 58-A)
AE Class B relay description and adjustment.
Manual / Guide · 1961
AE Class B relay description and adjustment.
RELAYS CLASS B AND CLASS C (TYPE 57 -A AND TYPE 58-A) Techni~al bulletin 961 - 537 GENERAL AUTOMATIC ELECTRIC ~ Subsidiary of GENERAL TELEPHONE & ELECTRONICS TCI Library www.telephonecollectors.info ( Factory, d evelopment laboratories, and general office at Northlake, Illinois, U.S.A. c AUTOMATIC ELECTRIC COMPANY is an organization of d esignin g, e n gineering, and manufa cturing sp ecialists in the field s of communication, electri cal control, and allied arts. For more than sixty years the company has b een known throu ghout the world as the ori ginator an<l parent manufacturer of the Strowger Automatic Telephone System. Today Strowger-t yp e equipment serves over 75 % of the world's automatic t ele phones. The same exp erien ce an<l t echnique that have grown out of the work of Automatic El ectric engin eers in the fi eld of t elephone communication a r e also b eing su ccessfull y applied on an ever-increasing scal e to th e solution of electrical control probl em s in bu siness and industry. PRINCIPAL PRODUCTS Strowger Automatic Tele phone Systems- Co mpl e te automatic ce ntral-offi('e equipm e nt for exchange areas of any size, from s mall town s to th e largest metropolitan ne two rk s. Community Automatic Exchanges- Unattended automatic units for s mall rural or suburban areas, with fa c iliti es for s wit1· hin g into attended exchanges. Automatic Toll Boartl s - An adaptation o f Strow ge r prin c iples to toll switching, r esultin g in simplifi cation of operators' eq uipm e nt and greater eco nomy of ope rating and toll-circui t time . Private Automatic Excharrges - Avai labl e in variou s capacities, with or without ce ntral-o ffi ce ( co nnecti o ns, and with faciliti es for sp ecial control services to meet the n ee d s of the u ser. P.B.X. S witchboartls- A compl e te range of cordless and co rd t ypes for the m ode rn bu sin ess. T e l e phone In st ruments - Modern designs for automatic or manual exc h a n ges, including th e Mono phone-th e world's mo st attractive and e ffi1'.icnt h a nd se t telephon e. Exchange Accessory Equipment - A uxiliary e xr h an ge an d s ub station e quipment , including manual de s k s, t es tin g apparatu s, t ra n s mi ss ion e quipm e nt , and a ll ac cesso ri es n ee d e d for th e ope rati o n and maintenance of the mode rn teleph o ne e xchange. ( Make r s also of electrical eontrol apparatus for indus trial, e ngineering, and public utility companies, te l e phon e apparatus for railroad s and pipe-line , companies, privat e telephone ~ ~· s tems of all t~· p es, electrical and communication devices for aircraft and airways control , and spec ial communication apparatus for military and naval departm e nts. ( ' Copyright © 1961 Automatic Electric Company TCI Library www.telephonecollectors.info ( CONTENTS Page 3 1. INTRODUCTION . 1.1 Physical description 3 1.11 Class B relays 1.12 Class C relays 3 4 1.2 Applications . 4 1.3 Things to consider when ordering 4 2. DESIGN AND CONSTRUCTION. 6 2.1 Contact assembly . 2.11 2.12 2.13 2.14 2.15 6 Self-cleaning contacts Basic contact arrangements Selecting the contact Springs Spring buffers 2.2 Armature 7 7 7 7 8 8 2.21 Short-lever versus long-lever armature 2.3 Heelpiece 9 10 11 3. DIFFERENT TYPES 3.1 Quick-acting relays 12 3.2 Slow-releasing relays 12 3.3 Slow-operating relays 13 3.4 Slow-acting relays 13 3.5 Snap-action relays 13 3.6 Special features 14 4. ORDERING REPLACEMENT PARTS . 14 4.1 Explanation of right- and left-hand pile-ups 15 4.2 Coils for replacement 16 5. MOUNTING 16 5.1 Individual mounting bracket 16 5.2 Mounting strips 17 5.3 Plug-in mountings 17 5.4 Relay covers 17 5.5 Hermetically sealed relays 17 . 5 .51 AE 700 enclosure 5.52 AE 600 enclosure . 5.53 AE 6100 enclosure 6. MAINTENANCE . 17 18 18 18 TCI Library www.telephonecollectors.info ( ( ( Class B relay with long-lever armature (most widely used) Class B relay with short-lever armature ( Class C relay ( ( Frontispiece. Typical class Band class C. relays. ( TCI Library www.telephonecollectors.info ( \ CLASS B AND CLASS C RELAYS ( ( ( (TYPE 57-A AND TYPE 58-A) 1. INTRODUCTION The Class B and Class C relays are generalpurpose telephone-type relays of the most modern design, for horizontal or verti cal mounting. Both classes have many identical features, the main difference being that the Class C relays are approximately half the size of Class B relays and thus mount in much smaller space. There are several different types available in each class and these will be discussed in §3. With so many different types available and with the c hoice of many design features (see §2) it is possible to obtain a relay engineered to meet the requirements of almost any particular application. Some of the general advantages of Class B and Class C relays are: small mounting area, high sensitivity, independent twin-contacts, centered dome-type spring buffers which obviate ''wearingin", sturdy armature arms, simple and permanent adjustment, heavy-duty armature bearing and yoke, self-cleaning contacts, adjustable or fixed residuals, and (particularly Class C) spacesaving compactness. 1.1 Physical description 1.11 Class B relays: Class B relays extend 3 17/32" beyond their mounting (see figure 3) and the over-all length is 4 3/32" The width of the relay depends, of course, on the number of .* *Approximately 1/3" less if there is no residual screw (i.e., if welded-di s c r esidual is used). Disc residuals are furnished unless residual s crews are specified. Stationary (MakGt) Sprinq J ArmaturGt (Movable) Sprinq s,,;,, ~erminals ( Clamp Washer Coil TGtrminal ( Armature Bearinq Pivot Pin / \ Armoture Arm (Lonq-Lever) Figure 1. Typical class B relay. TCI Library www.telephonecollectors.info 3 INTRODUCTION Spring combination -~- mount~,q screws - - - - - - - - - 4 32 Insulator Double hole washP!' (punch side down} Typicalr11~ Yoke Clamp washer sprinq assembly Heel ~ piece-----t Shoulder --==::::::;:f'1 bushinq for :rt)_.I l<D - en C\J •!:::I (\I ,,, (\J I") _[ 8 4temunal coil Residual screw Hei1.agon residual .75d' C:nil t· lfl&ln 1nq I" 132 screw Figure 2. nut Coil Not required ~en amature with welded disc type residual is used. Typical class B relay with short-lever armature. contact springs, being 1 9/16" m1mmum (2 springs) to 2 27/64" maximum (13 springs). The height of the relay is 1 1/32" which permits li" mounting centers. The maximum number of springs on the Class B relay without a cover is 13 springs in each pile-up. With a standard size cover the maximum is 8 springs in each pile-up. For industrial applications a special cover accommodating a maximum of 13 springs in each pile-up is available. 1.12 Class C relays: Class C relays are of essentially the same length as Class B relays, namely 3 15/32", and the over-all length is 4 1 / 32" . The width of the re lay is a rmmmum oft" for two springs and a maximum of 2 1/32" for 13 springs. The height is 21/32" (see figure 4). * 1.2 Applications Because of their superior design and longwearing qualities, Class B and Class C relays may be used for a wide variety of applications. Class B relays are used primarily for telephone 1 circuits, calculating machines, power supervisory equipment, electronic control circuits, coinoperated devices, and many other such applications. Class B relays are used where high sensitivity, extremely dependable performance, freedom from frequent maintenance, and long wear are required. Class C relays incorporate the same characteristics as Class B relays but 1 are approximately only half the size and thus can be utilized for the same applications where space saving and weight reduction are important. 1.3 Things to consider when ordering *Approximately 113 less if there is no residual screw (i.e., :if welded-disc residual is used). Disc residuals 11 are furnished unless residual screws are specified. 4 When our relay engineers know as much as possible about your requirements, they can TCI Library www.telephonecollectors.info INTRODUCTION ~~-Spring combination mounting screws 4 3· _32------- Double hole washer Typical sprinq assembly piece_ __ Heel " °'IN Nrt) Shoulder--for ~r---''-+.l"'-'-11 _ 4 termnal t:I~ coil ~"l--fllt-+--r- bushinq HeisQCIOfl L Figure 3. Not required when armature with welded disc type residual is used. Typical class B relay with long-lever armature. select the best relay for each particular application and circuit condition. It is advisable to give us complete information about your circuit and its operation, avoiding too narrow specifications, which may be neither necessary nor commercially practicable. Where limits are specified they should be in the nature of either tolerable maximums or tolerable minimums, not both. In ordering a relay, specify the following: b. Class of relay desired (Automatic Electric Company Class B or Class C). if critical. If current is not critical, our relay engineers will select an economical coil for the voltage available, and should not be hampered in selecting an ideal coil by having current limitations imposed. d. Spring combination (see figure 5). e. Contact load (see figure 7). f. Type of contact load -- whether inductive, resistive, or capacitive; voltage a.c. or d.c. g. Timing requirements only if critical. (Relays typically operate in less than 25 milliseconds.) If timing is critical, specify only a maximum or only a minimum rather than a range; e.g., ''no"t over 20 milliseconds,'' rather than "10 to 20 milliseconds". h. Frequency of operation, i.e., approximately ------ operations per day or year. Operating coil voltage (nominal) a.c. or d.c. If voltage is unstable, what is the minimum to which it falls? The maximum, that might produce over-heating? c. residual nut Coil Coil . mount1nq screw 8 a. Residual screw Operating current (maximum or minimum milliamperes available in the circuit), only TCI Library www.telephonecollectors.info 5 DESIGN AND CONSTRUCTION 2.1 Contact assembly It usually is not desirable to specify minimum contact pressure because this introduces gramgauging operations during production, which increases the price and slows delivery. All our relays are designed to provide adequate contact pressure, providing reliable operation for years. The most important part of a relay is, of course,\ the contact assembly; the contacts must make and/or break as required by the circuit in which the relay is used. To insure perfect contact at all times, each of the twin contacts on each ( spring of Class B and Class C relays is independent and self- cleaning. The springs have di verging tips that are widely separated to simplify adjustment, and to insure independent operation of each contact. This design has been found to be remarkably free from contact "bounce" and "chatter", and such bounce and chatter of the contacts as does exist is largely I masked by the different length, stiffness, and vibration frequency characteristics of the disimilarly shaped spring tips. Elimination of this much of unwanted spring contact opening is helpful in critically ti.med circuits, and reduces contact wear from mechanical rubbing, with resultant increase in contact life. Electrical arcing is also reduced by the improved contact stability. The tips of the springs are free to adjust to the slightest pressure exerted on the 2. DESIGN AND CONSTRUCTION Class Band Class C relays are general-purpose relays which are manufactured in many different standard assemblies from which one can select to meet each particular application. The types available in each class are discussed in §3. The spring pile-ups can be arranged in almost any form, order or combination required by the circuit. This flexibility in contact-spring arrangement and contact material and form, combined with proper coil characteristics, required adjustment, choice of two armature ratios, and choice of right-hand, left-hand, or double-arm armature enables you to obtain a relay ''custom tailored'' for each specific application. ~3~~ I Yoke shim ----~ ---------4fz----Special insulator Typical sprinq assembly Double hole washer liillllliii!ll!~~~/Clamp I • / -Yoke screw -Armature auembiy waiher Standard insulator Heel .._,~ • r:: If) co piece--~--i Coil mountinq screw--~-1 Coil Figure 4. 6 Residua I screw ;h '---- Heiwqon residual nut"J Not required----~ when armoture with disc type residual is used. Typical class C relay. TCI Library www.telephonecollectors.info .I DESIGN AND CONSTRUCTION spring. The circuit is thus completed through one contact if the other contact should be held open by dust or foreign matter. The twin contacts also somewhat increase the current-carrying capacity of the relay. 2.11 Self-cleaning contacts: The armature (moving) spring and the break or make (stationary) spring of each contacting pair are made of different shapes and thicknesses and have different flexing lengths. This difference in flexing lengths means the path of movement of the armature- spring contacts is on a different radius than that of the stationary-spring contacts. This difference in the direction of movement makes the contacts rub or wipe sufficiently to break through a film of dust or dirt without excessive mechanical contact wear. This selfcleaning action insures positive circuit contact. The dome shape of the contacts also aids in the self-cleaning action. This dome shape is also more resistant to mechanical wear. (Other contact shapes may require consideration of polarities and thus handicap circuit design.) Contacts on Class B and Class C relays are welded to the spring which also adds to the sturdy construction and long-wearing qualities of these relays. 2.12 Basic contact arrangements: The basic contact arrangements (figure 5) are shown in their normal positions. These can be arranged in almost any order or combination. Unless otherwise specified the contact arrangement will be supplied per the standard order of assembly (figure 6). The code letters "A" to "D" are used to describe the basic contact arrangement or "form". The number of forms required is indicated by a number preceding the ''form'' letter. They should be specified in the order in which they are assembled starting from the heelpiece. For example, the spring pile-up shown in figure 6 would be ordered "lBlClElAlD". The Class B relay can have a maximum of 26 springs (13 in each pile-up). The maximum number of springs obtainable with the Class C relay is 13 (right-hand pile-up only). Class B relays with the long-lever armature can have only one "D" combination in each pile-up and it must be on the outside of the spring pile-up. If two or more "D" combinations (in each pile-up) are necessary, use the short-lever armature. ~ 0 t~· • Form B •Break" Form A "Make" Figure 5. o----i o---n Form C •ereak-make• Form D •Make-beforebreak• t:==t• t~~ •t Basic contact forms. new alloys and in broadening the uses of some contact materials, there is no all-purpose contact material which both works well in, and is economical for, all applications. Many variables influence contact life and performance. Materials like silver have excellent conductivity but are subject to filming, transfer, and pitting. Tungsten on the other hand is highly resistant to mechanical wear and arc erosion but requires relatively high contact pressure and applied voltages. Selection of a relay contact material therefore involves choice of a material which will give good performance despite its inherent disadvantages. The information requested in §l.3f and §l.3h enables us to best select suitable contacts. One contact material may work fine in one application and not in another. Over a period of years Automatic Electric Company has tested and used many different contact materials. Figure 7 lists materials normally used and recommended for Class B and Class C relays. Code 0-18 is supplied unless the information under § 1.3 f indicates another material will be preferable. 2.14 Springs: The springs on Class Band Class C relays are of identical design (see figure 8). The armature springs and break or make springs are of different shapes and thicknesses of nickel silver. They are assembled, then tightened and secured under pressure which =.':~.~~<>-------I• :::::::J I E Jo-----.---ARMATURE SPRINGS BREAK OR BACK SPRINGS \_ SPRING BUFFERS ~7 II- ARMATURE ~-HEELPIECE 2.13 Selecting the contact: Although considerable progress has been made in the development of Figure 6. Contact-spring standard arrangement. TCI Library www.telephonecollectors.info 7 DESIGN AND CONSTRUCTION CODE DIAMETER MATERIAL BREAK OR MAKE LOAD WILL CARRY LOAD 0-18 0.067" 50"/o silver 50% palladium 135 watts (max. 3 amp) 150 watts (max. 3 amp) To be used for all ordinary applications. Resistant to tarnish and non-microphonic. 3-18 0.067" 85"/o gold, not more than 15"/o alloy 50 watts 150 watts To be used for low-level or for "dry" circuits. Reliable. Short life, subject to mechanical wear, high metal transfer. 9-18 0.067" 96"/o platinum 4% ruthenium 135 watts (max. 3 amp) 150 watts (max. 3 amp) Very resistant to mechanical wear - hence long life. Tungsten* 0.125" Tungsten 450 watts (max. 2 amp) 450 watts (max. 2 amp) Recommended for highly inductive, low-current circuits. Available with single contacts only. Silver tungsten* 0.1875" Silver tungsten 450 watts (max. 4 amp) 650 watts (max. 6 amp) Available with single contacts only. Silver tungsten* 0.25" ** Silver tungsten 575 watts (max. 5 amp) 1150 watts (max. 10 amp) Available with single contacts only. RECOMMENDATIONS *When these heavy-duty contacts are required, the short-lever armature is recommended. **When 0.25" diameter contacts are employed it may be advisable to use special highly conductive springs to minimize heating to prolong spring life. Figure 7. Cbntact materials. results in a very stable spring combination. The springs do not protrude beyond the edge of the heelpiece. The reduced over-all height of the relay saves mounting space. The number of springs or "spring load" affects the operating and release time of the relay since the relay does not operate until the magnetic flux has had time to build up. Fast release is aided in part by mechanical loading. Many factors contribute to the operate and release time of a relay (see §3) but if operate time or release time is critical, it may have to be considered when a particular spring pile-up is selected. 2.15 Spring buffers: Because spring buffers on Class B and Class C relays are subject to mechanical wear, they are made from mandrelwound phenolic rod. This material will not dust, wears down only imperceptibly during the life of the relay, and withstands very high temperature conditions without distortion. The top of the spring buffer is domed or rounded off rather than flat. The pressure falls on a small point in line with the center of the spring and is evenly distributed between the independent twin contacts. This dome shape eliminates "wearing-in". As the contacting spring flexes, it always rolls over the same point, thus it doesn't change the shape of 8 the buffer or cause unnecessary wear, which makes relay readjustment infrequent. On Class B relays with long-lever armatures, the buffers are mounted on the center line of the armature (moving) spring near the bifurcation of the spring. On Class C relays, and on Class B relays with short-lever armatures, the spring buffers are mounted on the center line of the armature springs on the free end of the spring (see figure 8). 2.2 Armature Class B relays are available with two armature ratios. For the long-lever armature, the ratio of buffer travel to armature travel is approximately 1.65 to 1 (figure 9). This leverage ratio for Class B relays with short-lever armatures and for Class C relays is approximately 1.15 to 1. Class B relays are available with either long- or short-lever armatures, each of which is available in right-, left-, or double arm. Class C relays are available only with the right-hand short-lever armature. Both are available with either a welded (fixed) residual or a screw (adjustable) residual. The working ends of the armature arms are formed inward so they lie over the back of the heelpiece but are kept from contact with it by TCI Library www.telephonecollectors.info DESIGN AND CONSTRUCTION a non-magnetic metal shield to prevent magnetic freezing of the armature arm. Thus no backstop, no backstop adjustment, and no field replacement due to breakage are required. Class B and Class C relay armature bearings are of the pin type, greased to give long life under all conditions. The armature, the bearing pin, the yoke, and the bearing plate are assembled on the relay with a clamping washer. This makes the armature suitable for both light- and heavy-duty applications. 2.21 Short-lever versus long-lever armature: No more work can be obtained from a system of levers than is put into it. If a long lever lifts a weight, the small force travels a great distance. The choice of length is governed by the available force or by the distance through which the force may go to produce the required work. In the case of relays, the choice of length is governed by required operate and release times, load, and available power. The movement and force ratios in these two armature-lever lengths are shown in figure 9. The dimensions along the armatures show the simple ratios of the arms themselves. A spring can be considered as a lever where the fulcrum is at the insulator, the load is at the contact, and the force is applied at the buffer. The two small sketches at the bottom in figure 9 show an additional point: in a relay with longlever armature, the contact moves farther than the buffer, but in a relay with short-lever armature the contact moves less than does the buffer. Thus, the long-lever armature relay with an air-gap-to-buffer-movement ratio of 1: 1.65 has an air-gap-to-contact-movement ratio of 1 :2.4. The short-lever armature relay with an air-gap-to-buffer-movement ratio of 1: 1.15 has an air-gap-to-contact-movement ratio of 1: 1. Short-lever armatures are recommended for relays that are to be slow to release, such as d-c relays with release-delay requirements too long for long-lever armatures, a-c relays, and relays operated from ~-wave-rectifier power. The short-lever armature ratio gives contact springs less leverage to restore the armature; i.e., gives the relay coil greater leverage to hold the relay operated. Advantages of the shortlever armature in special situations are: a. Prevents chatter in an a-c relay, by giving the shading-coil flux mechanical advantage. OPERATED BUFFER LOAD 100 GRAMS 00 Buffer Buffer cup ARMATURE LEVER lLONG) Typical armature spri119 (for relay with short-lever armature} Contacts~ Buffer Buffer cup Typical armature spring (for relay with long-lever armature) Figure 8. Typical armature springs. ARMATURE LEVER (SHORT) di LONG LEVER ARMATURE DIAGRAM SHORT LEVER ARMATURE DIAGRAM F1:gure 9. Lbmparison of leverage ratios of long- and s/wrt-lever armatures. TCI Library www.telephonecollectors.info 9 DESIGN AND CONSTRUCTION CLASS B TYPICAL OPERA TING TIME SECONDS TYPICAL RELEASE TIME SECONDS MAXIMUM COIL VOLT AGE MAXIMUM NUMBER OF CONTACTS Quick-acting BQA 0.003-0.030 0.002-0.050 250 de 26 springs Slow-operating BSO 0.040-0.120 0 .02 5-0 .350 135 de 26 springs* Slow-releasing BSR 0.015-0.035 0 .035-0 .600 135 de 6 springs** Slow-acting BSA 0.020-0.055 0 .035-0 .600 250 de 6 springs** Quick-acting a-c BFA 0.010-0.025 0.008-0.020 230 ac 26 springs Snap-action BMS 0.010-0.030 0.015-0.050 250 de 20 springs & 2 form "C" *Up to 0.600 second release time with not over 6 springs. **More contacts can be accommodated at a sacrifice of operating speed and release time delay. CLASS C TYPICAL OPERATING TIME SECONDS TYPICAL RELEASE TIME SECONDS MAXIMUM COIL VOLTAGE Quick-acting CQA 0.005-0.035 0.005-0.025 100 de Slow-acting CSA 0.010-0.040 0.015-0.200 100 de 13 springs Snap-action CMS 0.010-0.035 0.010-0.050 100 de lC snap-action switch only Figure 10. b. MAXIMUM NUMBER OF CONTACTS 13 springs Typical operating and release times. Enables a-c relays to hold firmly operated a heavier spring load than would be possible with a long-lever armature. Make contacts of some a-c relays might otherwise flatten after relatively short service due to imperceptible fluttering, which would wear away the contact faces. This is eliminated in well-designed re lays having short-lever armatures. c. A slow-release d-c relay, with a short-lever armature, will remain operated longer after de-energization than will a similar relay with the same spring load and a long-lever armature, thus providing longer and better controlled release time. d. A short-lever armature provides a required release time for a heavily loaded slowrelease d-c relay with a larger ''residual'' setting than is possible with a long-lever armature. Armature "sticking" from residual magnetism is prevented. If an adjustable residual is used, the relay will need little if any readjustment during its entire life. Slight wear or flattening of the residual disc or screw therefore will affect release timing only slightly because the residual gap was larger originally. Before the widespread use of the shortlever armature, release time was adjusted through the residual gap. Without a shortlever armature a too small residual gap is often unavoidable. With a short-lever armature and a well-designed relay, a large residual gap is always possible. The short-lever armature is not advantageous for all relay applications. The long-lever armature travels less to actuate the contact springs, so is faster acting (an especially desirable feature if frequent short pulses must be followed rapidly). For all ordinary purposes where there is no actual need for a short-lever armature - use a long-lever armature. 2.3 Heelpiece 10 Class b and Class C relays have very sturdy heelpieces to give the spring pile-up great stability of adjustment. The heelpiece is made of heavier-than""usual zinc-plated magnetic iron, which results in great flux-carrying capacity. This heelpiece is engineered to minimize magnetic leakage for greater sensitivity (all the flux generated links the armature, doing useful work). When the release time of a fast-acting relay is very critical and must remain constant even under conditions of varying magnetic saturation and age, most Class B and Class C relays can be supplied with nickel-iron heelpiece and coil core. TCI Library www.telephonecollectors.info DIFFERENT TYPES 3. DIFFERENT TYPES e. Several different types.are available in both Class B and Class C relays. There are various types in order to meet different timing requirements (see figure 10). Many factors affect the timing of the relay. If timing is critical, you may wish to consider the following before ordering a relay: a. Contact spring load The relay armature does not operate until the magnetic flux has had time to build up to the required value, and this time varies (other factors being constant), with the mechanical loading. A light contact spring load may decrease the operating time and increase the release time; a heavy contact spring load may increase the operating time and decrease the release time. b. Armature stroke A shorter armature stroke tends to decrease the opera ting time; a longer stroke to increase the operating time. c. Residual gap Increasing the residual gap tends to decrease the release time, and decreasing the residual gap tends to increase the release time. Since, for a standard stroke, an increase in the residual gap will require an increase in the distance of the armature from the core at the start of its stroke, it also tends to increase the operating time. Where release timing especially is critical, a screw-type residual is recommended. Spring gauging Increasing the make-contact gauging increases the armature restoring force and will tend to decrease the release time, and, conversely, decreasing the make-contact gauging will tend to increase the release time . f. Copper collars and sleeves on coils When the core of a relay is encircled by a solid ring of copper, any change in the flux produced by the current flowing in the coil winding will tend to be opposed by momentary current in the copper collar or sleeve (Lenz' law). The extent to which the flux change will lag behind the primary-coil current change increases with an increase in the amount of copper in the collar or sleeve. Various size collars and sleeves are used by the relay engineer to achieve the required operate and release time (see figure 11). A copper collar on the heelpiece end of the coil core has just a small effect, causes a slight delay, on the operate time of the relay; it causes a greater delay in the relay release time. A copper collar on the armature end of the coil core or a copper sleeve the full length of the coil core both have the effect of making the relay slow to operate and slow to release. The copper sleeve the full length of the Operate and release timing for a typical slow-acting relay. " Inductance of the coil I ... -- '~ -- -- I-'" '7' ./ v ~v ,l~ j .... ~ IY / - - ~ .~ ./ .r ,, ,, I / I" .,, ,, ~ loC rO ,p ./ v ,/' ../ I I /" v v -~ ¢" 'I~ '7 _....v v"'" I Increase of roil inductance will increase the operating time, other factors remaining constant. A relay which gets its required ampere-turns from a coil with a few turns and relatively high current will operate more quickly than one with many turns requiring less ctlrrent (other effects being equal). Increase in circuit voltage decreases operate time. The effects of inductance can be lessened by use of a non-inductive resistor in series with the relay coil. .. ,..( ...... ,,,,~~- / :..~ ~- _,..v_, p"'"' / ...e v d. v v ./ n(C ~ -· ~\)~ v \\ ... :__,,.. I--"' t 0 v- _..;:;-" '-e e I--""'.- ,. l ' " Volume of copper in cubic inches +----+---+--,,-+-,-,-+-,Outside diameter of sleeve .43?6 .500" Length of collar 7" T6 .562 .594 .626 I II" 16 I" Figure 11. Operate and release timing of a typical slow-acting relay. TCI Library www.telephonecollectors.info 11 DIFFERENT TYPES rrn:---31 -------~--11__________ Armature Copper collar Copper collar Heel piece Heel piece I Magnetic flWI path immediately ofter coil circuit cloeure. 2 Magnetic flu11 path a moment later. 3 Final flu11 links collar. Collar now can delay release. Figure 12. Effect of heel-end collar. core has the greatest effect on both the operate and the release delay times per unit of copper. However, since the maximum amount of copper that can be used in a sleeve is limited to approximately one-half the amount usable in an armatureend collar, maximum operate and release delay times are obtained by use of the armature-end collar. Heel-end collars have the adv ant age of producing a significant release delay time, but delay the operate time only slightly. If both a.c. and d.c. flow in a circuit, the combination of a sleeve and an armatureend collar on relays intended to operate on d.c. only, will make them so sluggish they will not respond to a.c. (ringing-cut-off relays in telephony, for example). g. Nickel-iron coil core and heelpiece A standard relay ordinarily will have a ratio of release to operate power of approximately 50%. For quicker release, nickel-iron alloy is recommended for the coil core and heelpiece. When a relay must release on a value of current as close to the operate value as possible, other nickeliron parts are used. Sometimes a circuit of nickel-iron is employed throughout, even in the armature. A ratio of release to operate power of 75% is attainable under ideal conditions (one back contact and not to exceed 5 springs). h. 12 Armature I Magnetic flux path immediately after coil- circuit closure. 2 Magnetic flu11 path a moment later. 3 Final flu11 link• armature to cause operation. Figure 13. Effect of armature-end collar. slow-to-release or a-c-operated relays, the short-lever armature is usually used. It permits employing a larger residual gap, and delays release longer on d.c., or provides quiet operation on a.c. Since some factors that speed operation also retard release, careful balancing of all factors is necessary in critical timing applications. 3.1 Quick-acting relays Quick-acting relays are available in both Class B (series BQA and BFA) and Class C (series CQA). Series BQA may be used for normal operatingand release-time requirements; also fast operation and marginal operation. These relays can be supplied with multi-wound coils, fixed or adjustable residuals, and 1 or 2 pile-ups with a maximum of 13 springs in each pile-up. A longlever armature and fixed residual are standard on series BQA relays .. The series CQA relay is recommended for use as a general-purpose relay to mount in minimum space. These relays use a single- or doublewound coil, 1 pile-up with a maximum of 13 springs, and a short-lever armature. They may be supplied with an adjustable residual, but a fixed residual is standard. The series BFA is a quick-acting relay for a-c operation. It is provided with shading coils to prevent fluttering, and the short-lever armature and fixed residual are standard. Armature ratio 3.2 Slow-releasing relays For normal operating and release time, the long-lever armature is most efficient. For The slow-releasing relay (series BSR) provides a large release-time delay with little delay in TCI Library www.telephonecollectors.info DIFFERENT TYPES c ( ( operating time. These relays have a copper collar around the heel-end of the coil core, small residual gap, and a relatively light contact load. The copper collar retards the collapse of the magnetic field once it has been established, thus providing a release time delay. Figure 12 shows how the effects of the counter e.m.f. of the heelend collar result in early linkage of the armature but, after the circuit has been maintained for a fraction of a second, the flux soon links the collar steadily. On de-energization, the counter e.m.f. of the collar maintains the flux long enough to produce a release-time delay of 0.035 to 0.600 second. An example of a coil with a heel-end collar is shown in figure 14. Where greatest possible delay is desired, or where permanence of the timing adjustment is very important; a short-lever armature is recommended. It is advisable to limit the spring pile-up to not over 6 springs. More springs may be added but at a sacrifice of release delay. Because of slow contact separation and consequent tendency to arc, these relays (BSR) are not recommended for use in breaking heavy current or highly reactive loads. ( 3. 3 Slow-operating relays ( Slow-operating (series BSO) relays use a copper collar on the armature-end of the coil core to retard magnetic field build-up. With the collar on the armature-end of the coil spool (figure 13), the flux fir st leaks inside the collar when the coil winding is energized. Later the transient effect of the collar allows the flux to build out until it acts upon the armature. This time interval, during which the collar is effective to prevent magnetic attraction of the armature, is referred to as "operate time delay". It varies (depending on the length and thickness of the copper collar) from 0.040 to 0.120 second. After the magnetic flux is established in full linkage with the collar, the counter e.m.f. of the collar also delays the collapse of the magnetic field when the coil winding is de-energized. The armature-end collar, therefore, delays both operation and release. These relays may be used with a heavy contact load; in fact a heavy contact load helps delay operation. These relays can have 1 or 2 pile-ups with a maximum of 13 springs in each pile-up. ( ( No Collar Armature-end Collar Figure 14. Heel-end Collar Typical relay coils. acting relays employ coils with a copper sleeve around the full length of the coil core to reduce effective inductance of the winding and to provide both operate- and release-time delays. However, the operate-time delay is not so great as in the series BSO. The short-lever armature and the adjustable residual are recommended for use with series BSA and series CSA relays. 3.5 Snap-action relays Snap-action relays (for contact loads greater than can be handled normally on open contacts) are available in Class B (series BMS) and Class C (series CMS). These are sensitive relays designed for switching heavy a-c loads. They may be used in locations subject to sudden jarring, vibration, or tilting for which mercury contacts are not suitable. Series BMS relays are furnished with one snap-action switch over each pile-up of up to ten springs; series CMS are furnished with only one snap-action switch over the sole pile -up of up to ten springs. Depending on the number of snap-action switches, the combinations are known as "lC" or "2C". 3.4 Slow-acting relays Slow-acting relays are available in Class B (series BSA) and Class C (series CSA). Slow- Figure 15. Typical snap-action relay. (The one shown is a class C.) TCI Library www.telephonecollectors.info 13 ORDERING REPLACEMENT PARTS 3.6 Special features h. Phenolic tubes slipped over the pile-up ' assembly screws provide added insulation between the springs and the heelpiece. Many special features are available for both Class Band Class C relays. These special features include: a. i. Hermetic sealing See §5.4. b. Impregnated coils "High-pot" coils Our standard test potential is 500 volts r .m.s • Any voltage above this is "high-pot". We test our "high-pot" relays at 1,250 volts; ordinarily they withstand surges up to 1,500 volts. High-pot coils have extra insulation around the core, and phenolic fillets rounding corners between core and spool head. d. j. "High-pot" relays k. "Tropical" and "semi-tropical" treatment For use in tropical climates or salt-spray atmospheres, relays are supplied with fully impregnated coils and are given fungicidal treatment. g. Double spring insulation Class B and Class C relays can be supplied with two insulators instead of one, placed between the springs. This reduces capacitance and increases the insulation resistance between the springs, but not between the springs and heelpiece. 14 Electrostatic spring shielding Because adjacent contact springs are of different shapes, capacitance effects are lower than with straight springs. However, where desired, relays can be equipped with electrostatic shields between the two springs of each contacting pair, between contact forms in one spring pile-up, or between two spring pile-ups. Humidity treatment Relays to be used whe.re conditions of extreme humidity will be encountered are equipped with impregnated coils, and 'the spring pile-ups are moisture-sealed. f. Low-resistance springs Low-resistance springs can be supplied to improve current-carrying capacity. Where both coils and springs must withstand peak voltages in excess of 500 volts a.c., high-potential-insulated coils and specially insulated spring pile-ups are recommended. e. Marginal or close differential operation Th~ coils, the springs, and the adjustments of Class B relays can be properly coordinated to make the relay release in response to a drop in coil current or voltage, even though the coil circuit is not opened. Where the "drop out" voltage is half or less than half the operating voltage, a standard relay with proper adjustment can be used. Where the difference between operating and "drop out" voltages is less than half, ''marginal" operation can be provided by rela