Small-sized low-voltage power transformers of TP type are designed for operation in moderately cold climates at an ambient temperature of -60 ... + 85 ° С and relative air humidity up to 98% at a temperature of + 40 ° С. Transformers of the TP type are used in power supply devices REA, ACC and devices for powering functional units and blocks manufactured on PPP and microcircuits using printed wiring circuits. Transformers of the TP type (on armored magnetic circuits) have a power of 5, 200 V A, and are designed for an alternating current supply voltage of 20 x 2.40 and 115 V and a frequency of 1,000 Hz.
General view, overall and installation dimensions of power transformers of TP type are shown in Fig. 2.15. In the manufacture of transformers, armored magnetic cores of a standardized series are used, of the SHL and SHLO types. The list of used magnetic conductors is given in table. 2.24. The design of transformers and modern technology for their manufacture ensure durability and reliable operation under mechanical and climatic influences, discussed in the first chapter of the handbook. It is able to remain operational at high humidity and in all cases of temperature effects, to provide the necessary margin of safety for the insulation of the windings. The main structural dimensions of transformers of the TP type are given in table. 2.24.
Transformers of the TP type are assigned symbols that are used in the development of design documentation and when ordering the manufacturer. The transformer designation includes its abbreviated designation and designation GOST or TU, according to which they are delivered to the consumer. An example of a record of a small-sized transformer type TP for printed wiring schemes in the design documentation - "Transformer TP86-20-1000T".
Basic electrical diagrams of transformers of the TP type are shown in Fig. 2.16.
During installation, the transformers are installed in the sockets of printed circuit boards made with a grid pitch of 2.5 mm. Limit deviations of the installation dimensions and the gap between the axes of the base terminal and other terminals of the transformer shown in Fig. 2.14 are ± 0.05 mm. The base terminal of the transformer is marked with the number "0".
Technical characteristics and main parameters of power transformers for printed wiring circuits of the TP type, designed for a power supply frequency of 1000 Hz in rated load mode are given in Table. 2 25. Electrical parameters of transformers in idle mode are given in table. 2.26. The insulation resistance between the windings of the transformer in normal climatic conditions is 100 megohms. The insulation resistance between the windings and the case is 20 megohms. With short-term exposure to high humidity, the insulation resistance decreases to 10 MΩ, and with prolonged exposure - to 1 MΩ. Without breaks in the windings and changes in the no-load current, the transformers withstand repeated cyclic exposure to low and high temperatures, taking into account the overheating of the windings.
The minimum value of the probability of no-failure and highly reliable operation of transformers for 1000 hours with a reliability equal to 0.9 is ensured within the limits of 0.997, .. 0.999.
Power supply of transformers from the primary AC network with a voltage of 20 x 2.40 and 115 V is carried out with voltage and frequency fluctuations within ± 5% Operation of transformers with a rated voltage of 40 V from a network of 37.6 ... 42.4 Vis with a rated voltage of 115 V from a network is allowed 108. .122 V when voltage is applied to the corresponding taps and terminals. Stable operation of transformers is ensured when the frequency of the supply network changes within 950-5000 Hz. The mains voltage is applied to the terminals "1" and "2" or "1" and "4" of the transformer. Under normal operating conditions, the transformer has a service life of at least 10,000 hours.