1、in h n c 2 3 t Ly EIA 375 56 m 3234600 0028532 2 m - 7 ETMA STA Audio Inductors (Revision of TR-122) December 1956 Engnee ring Department RADIO-ELECTRONICS-TELEVISION MANUFACTURERS ASSOCIATION P- EIA 375 5b m 323Yb00 0028533 -4 m NOTICE RETMA standards are adopted in the public interest and are desi
2、gned to eliminate misunder- atandings between the manufacturer and the purchaaer and to assist the purchaser in selecting and obtaining without delay the proper product for its particular need. Existence of such stand- ards does not in any respect preclude any member or nonmember of RETMA from manuf
3、acturing or selling products not canforming to the standard. Any proposal of recommended standards and practices made by the Association is without any regard to whether or not their adoption may in any way Involve patents on articles, materials or processes. By such action, the Association does not
4、 assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the recommended standards or practices. Published by ELEXROIYIC INDUSTRIES ASSOCIATION Engineering; Department 2001 Eye Street, N. IV., Washington, D, C. 20006 Copyrlgbt 196 by R.di.Electronlcs-
5、Televioion Manufacturen, hcietlon AU rlghta renerved Brice $1.06 Printed lu U.S.A. EIA 175 56 3234600 0028514 b RS-175 Page 1 AUDIO INp%UCTOWS (From Standards Pyoposal No. 513 f ormuluted under the cognizance of RETMA Engineering Committee SQ-4 on Trunsformers and Reactors) 1. SCOPE This standard co
6、vers iron core inductors for use in e1:ctronic equipment in which long life, reliabil- ity, and continuity of operation are essential and which are employed for frequency discrimination elements or for filters other than power supply application. It also covers those characteristics of transformers
7、which are otherwise covered by the RETMA Audio Transformer Specification, but wherein one or more windings are employed as tuned elements. It is not intended that the frequency be limited to the region of audio frequencies. 2. DEJ?“ITION 2.1 Electrical terms used in this specification shall be in ac
8、cordance with those given in “Ameri- can Standard Definitions of Electrical Terms,“ ASA, C42, 1941, except as noted. 2.2 The RMS working voltage between any winding and any other winding or ground, shall be defined as 0.707 times the sum of the maximum dc voltage and the peak ac voltage which may ap
9、pear between that winding and the other winding or ground under normal conditions of con- tinuous operation. 2.3 Q is the ratio of the reactance to the effective resiatance. 3. PURCHASE SPECIFIWTXONS The purchaser will specify: O - 3.1 Electrical Requirements 3.1.1 The rated value of inductance with
10、 tolerances at approximately 25C. temperature. (a) This value should be specified with the following additional values representing mean or normal use: (b) Permissible variation of inductance over the temperature range requirements of the appli- cation (to be specified). (c) The permissible variatio
11、n of inductance over the frequency and voltage range of the appli- cation (to be specified). (d) Taps and tap tolerances if required. 3.1.2 The Q of the coil under conditions of 3.1.1. 3,123 If the coil is employed in a resonant circuit : Whether the circuit is in series or parallel con- nection, an
12、d the resonance characteristics desired, if this information is available, 3.1.4 *The limits of distributed capacity if of consequence in the application. 3.1.5 The inductive pickup in volts at a specified low frequency, and maximum field strength, measured as specified in 5.1.2. 3.1.6 Any significa
13、nt operating requirement not treated above, such as unusual surge voltages, non-sinusoidal wave shape, operating voltage to ground and permissible harmonic content under varying operating conditions. AC voltage or current. . . frequency. . . dc voltage and current superimposed, if any. 3.2 Constizic
14、tion 3.2.1 General Assembly. For example: exposed core and coil, end bell, sheet metal encased, hermetically sealed, dry or liquid-filled. NOTE : In specifying construction, cognizance should be taken of requirements imposed by 3.3.4 and 5, and 4.1. a EIA i175 56 m 3234600 0028515 8 m L RS-175 Page
15、2 3.2.2 Termirtais. FOY example : leads, screw terminals QI: solder luga. 3.2.3 Monciriing. For example : terminal end or opposite and. 3.2.4 Limiting dimensions and weight. 3.3 Conditions of Operation 3.3.1 Maximum ambient temperature at which the inductor is required to operate continuously. Unles
16、s otherwise specified, the maximum ambient temperature ahall be assumed to be 60C. 3.3.2 Maximum altitude if more than 5000 feet above sea level. 8.3.3 Duty cycle if not continuous. Time on and ratio of time on Under certan conditions it may be found impractical t attan the accuvacg specified above
17、in the measurement of Q. In such cams the method of measurement shall be a8 agreed between purchaser and manufacturer. (b) Where the application specifies limits of inductance or Q over temperature, voltage or frsquerzcg limits, tests shall be conducted at the extremes and mean values to assure comp
18、liance. Tests for magnetic pick-up shall be made in a field having the flux density and frequency sgeci- fied in 3.1.6. The field shall be uniform within 10% for a space having at least three times the largest dimension of the inductor under test. Orientation shall be varied to obtain the maximum vo
19、ltage. NOTE : Unless otherwise specified it shall be standard to use a field strength of 5 gauss for all inductors. 5J.2 Test,s for Pickup - - -_ _ , - r EIA 175 5b m 3234b00 0028516 T m . -a RS4 7s Page 3 5.1.3 Debctric Strength Teste (a) For inductors operating below 26 volts, the test applied fro
20、m winding to core or case, or between windings, shall be 500 volta RMS 80 cycles, or equivalent. (b) Inductors operating above 26 volta shall have a 60 cycle RMS test potential equal to twice the BMS working voltage plus 1000, applied between winding and core OF case. (c) The test potential shall be
21、 increased gradually (at the rate of approximately 2 KV per second) from zero to the specified value, maintained for a period of one minute, and decreased gradually to zero. (d) Since the application of test potentiale may impair the strength of the inductor insulation, any dielectric strength test
22、shall, if repeated, be made at not more than 90% of the specified test potential. 5.1.4 The inductor shall withstand the application to the winding of a test voltage equal to at least twice the voltage appearing across the winding as specified in 3.1.1. (a), and at a frequency equal to or greater th
23、an twice the lowest frequency specified in 3.1.1. For large inductors, higher values of test voltage may be necessary, to comply with requirements given in 3.1.6. 5.1.5 Surge voltage test. Where the surge voltage specified in 8.1.6 exceeds the dc voltage, the inductor shall be capable of withstandin
24、g an impulse test a8 described in ASA Standard C57.22- 1948, paragraph 22.116. The magnitude of the test voltage shall be as agreed between purchaser and manufacturer. e 6. MARWNG 6.1 Recomme+ided markings ares 6.1.1 Manufacturers name or identification. 6.1.2 Manufacturers number and purchasers num
25、ber. 6.1.3 Inductance. 6.1.4 Dielectric test voltage, 6.1.5 Maximum RMS working voltage. O 6.2 Each inductor shall be marked with at least 6.1.1 and 6.1.2 above. These markings shall be made, and all terminals shall be identified, in a manner which is legible and permanent. 7. MOISTURE RESISTANCE TE
26、STS Tests shall be made according to this section whsn specified by purchaser. 7.1 Following the Performance Tests in 5, the inductor shall be temperature conditioned by sub- jecting it to three consecutive temperature cycles, starting at room temperature, each cycle to consist of four steps of the
27、following duration and temperature. TABLE I Step 1 2 3 4 - Test Chamber Temp. 85 to 100 degrees C. 20 to 40 degrees C. -40 to -65 degrees C. 20 to 40 degrees C. Time 45 minutes 30 minutes 46 minutes 30.minutes 7.2 Humidity.Run. After conditioning, the inductor shall be placed in a humidity chamber a
28、nd shall be kept for 14 consecutive days in an atmosphere at a temperature of (65 f 3) degrees C. and at a relative humidity of (90 f 3) per cent. During this run all windings not connected to core OF case shall be maintained at a positive potential of 76 to 125 volts dc with respect to core or case
29、. The humidity chamber shall be provided with suitable thermal insulation and with a means for keeping the air in continual circulation, to the end that the atmosphere surrounding the inductor under test shall meet at all times the specified temperature and humidity conditions. o .- .- - . - - I. c.
30、 I EIA 375 56 m 3234600 0028537 I m RS-175 Page 4 7.3 Proof of Ferfoimance, Qn completion of the liumidity run, the inductor shall be removed from the chamber and allowed to stand in air at room temperature for 16 minutes, during which period any surface moisture may be removed with a dry cloth. The
31、 inductor shall then be given the follow- ing tests, in the order stated, and without delay between tests: 7.3.1. It shall withstand, without breakdown, the Dielectric Strength Test given in 5.1.3, except that the test potential shall be 600 RMS volts or 125 per cent of the RMS working voltage, whic
32、h- ever is greater. 7.3.2 It shall withstand, without breakdown, the voltage test of paragraph 5.1.4, except that the test potential shall be 125 per cent of the RMS working voltage. 7.3.3 It shall be given the Load Test of Appendix I starting within 16 minutes after completion of the induced voltag
33、e test and continuing until the temperature of the core or case shows con- stancy or three successive readings at intervals of at least 80 minutes. During this run the inductor shall be inspected frequently and any evidence of distress (such as cracking, dforma- tion, leakage of compound, or evoluti
34、on or steam or smoke) shall constitute failure. 7.3.4 The Q test described in 6.1.1 shall be repeated and the Q shall not differ by more than 10% from the value observed in the initial Q test (at the frequency specified in 3.1.1. (a) ). 8. CORONA Explanatory It is an established fact that corona has
35、 a detrimental eflect on insulation and, when pyesent in suflcient magnitude, will cause insulation failure. In general, the equipment manufacturer and the user share in the responsibilitg for the presence and the magnitude of corona: the manufacturer in the need for his designing ths equipment to m
36、inimize the presence of corona and the user in the need for his maintaining the equipment dra and clean to this same purpose. Both the presence and magnitude of corona are influenced by humiditg and temper* ture and are otherwise unstable. The measurement of corona serves, therefore, more to provide
37、 an indication of level that of an exact value. 8.1 The Measiirement of Corona 8.1.1 Measurements shall be made only on clean, dry inductors. 8.1.2 Measurements shall be made using the method and noise meter described in RETMA Engi- neering Bulletin No. 32 titled “Methods of Meaauring Radio Noise, 1
38、940” and using the circuit of Figure 3, thereof. 8.1.3 A test potential of 106% of RMS Working Voltage: (a) Shall, where practicable, be applied between the winding under test and the core or case with winding terminals shorted or : (b) Shall, where (a) is impracticable, be induced in the winding un
39、der test: while in either case, other windings and core are grounded. (a) On first measurement be less than the following limiting values 8.1.4 The magnitude of the corona level across insulation subject to damage by corona shall RMS Working Voltage (Kilovolts) Up to 8.6 8.61 to 16 Corona Level (Mic
40、rovolts) 1,000 2,600 (b) On second or repeated measurement, shall be less than twice the above stated limiting values. EIA 175 56 I 3234600 0028518 3 I RS-175 Page 5 Appendix 1 LQAD TEST 1. The inductor under test shall be mounted so as to be protected against drafts and shall not be subject to radi
41、ation from warmer objects. 2. The thermometer for measuring the ambient temperature shall be protected against trivial temperature changes by means of an oil bath or other mitable thermal delay device. The load tests may be performed at room temperature. 3. The thermometer for measuring the temperat
42、ure of the core OF case shall be secured in contact with the core or case by means of glaziers putty or other suitable material. 4. The applied voltage and current for the load test shall be as specified in 3.1.l(a). 5. The frequency for the load test shall be the frequency at which the inductor is
43、rated for con- tinuous operation, as specified in 3.1.1 (a). 6. The load test shall continue until the temperature of the inductor core or case shows constancy for three successive readings at intervals of at least 30 minutes. 7. The temperature of the winding (for copper) shall be computed by the r
44、esistance method using the following formula (A.I.E.E. Rule 13-207) : R r T = - (234.6 + t) - 234.6 t = reference temperature in OC. of winding. T = temperature in “C. of winding to be calculated. r = reaistance in ohms at reference temperature t. R = observed resistance in ohms at temperature T. In
45、 applying this method, the resistance (r) at reference temperature (t) shall be measured after conditioning the inductor for at least eight hours in a location free from drafts and until three consecutive temperature readings of the ambient and core or case taken at 30 minute intervals are constant
46、; and this constant temperature shall be the reference temperature (t) . The observed resistance (R) shall be measured as soon as practicable, and within 16 seconds after completion of the test run on inductors weighing less than 10 pounds. 8. The temperature rise of the inductor shall be computed by subtracting tlie temperature of the ambient air (as measured in paragraph 2) around the inductor at the end of the test from tlie temperature of the winding or of the core (whichever is higher) at the end of the te&. O ,
