ECA-174-1956-R1982.pdf

/- I - Audio Transformers for Electronic Equipment o ;i( F 8 H m 4 c RS-174 (Revision of TR-121) e e December 1956; Engineering Department RADIO- ELECTRONICS - TELEVISION MANUFACTURERS ASSQCIATION Copyright Electronic Components, Assemblies or (b) Shall, where (a) is impracticable, be induced in the winding under 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 Worlcing Voltage (Kilovolts) Corona Level (Microvolts) e Up to 8.6 1,000 8.61 to 15 2,600 (b) On second or repeated measurement, shall be less than twice the above stated limiting values. Appendix I The following table shall be standard for specifying impedance values to be used for transformer terminations : 4 ohms 8 ohms 16 ohms 38 ohms 150 ohms 600 ohms 2,400 ohms 9,600 ohms 40,000 ohms 100,000 ohms Appendix II LOAD TEST 1 . The load for each seconclary winding shall be an impedance having the value specified in 3 . 1 . 1 . 2. The transformer shall be loaded at the maximum output epecified in 3 . 1 . 6 , with dc current speci- fied in 3 . 1 . 3 , and duty cycle specified in 8.3.3. a Copyright Electronic Components, Assemblies and this constant temperature shall be the reference temperature (t) . The observed resistance (R) shall be measured as soon as practicable and within 15 seconds after the comple- tion of the test run on transformers weighing less than 10 pounds. The resistances of the wind- ings having the higher temperature shall be measured first. 4 10. The temperature rise of the transformer shall be computed by subtracting the temperature of the ambient air around the transformer at the end of the test from the temperature of the hottest winding or of the core (whichever is higher) at the end of the test. Appendix III The test circuit shown in Fig. 2 shall be used where applicable for determining balance in trans- former windings with reference to 2.7 and 3.1.7. The resistors Rt and R? should be of the precision type and of equal value. The source terminals should deliver to the transformer a voltage which has less unbalance by at least 10 db than the value specified in 3.1.7 as defined by 2.7 at any frequency within the frequency band specified in 3.1.4. The resistors shall be non-inductive within the frequency limits specified above, and the sum of the values of Ri and Rn shall be equal within 5% to the terminating impedance specified for the winding used as the source winding. This test may be used in conjunction with that specified in 6.1.6 to determine compliance of the transformer with 3.1.7. Test may be made at any frequency but 1000 cycles shall be used unless another frequency is specified. In general at the low frequencies, the element contributing to unbal- ance will usually be winding resistance and turns; in the middle frequencies, winding turns; and at the high frequencies leakage inductances and winding capacitance. An oscilloscope may be u?ed if the relative phase of the secondary voltage is of interest. The test i s not limited to two-winding transformers and the test circuit may be modified as required. Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 19:59:21 MDTNo reproduction or networking permitted without license from IHS -,-,- EIA 174 56 m 3234600 0028511 O m RS- 174 Page 9 - - STEP I- LONGITUDINAL VQLTAGE *2 STEP 2- TRANSVERSE VOLTAGE LONGITUDINAL BALANCE = 20 log 5 db. = , FIG. 2 Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 19:59:21 MDTNo reproduction or networking permitted without license from IHS -,-,-