Experimental Study of the Temperature Regime of Single-Layer Varnish-Protected Hermetically Sealed Microwire Resistors
Abstract Generated abstract
This study examines the thermal regime of single-layer hermetically sealed microwire resistor models operating under natural convection at different ambient temperatures. Models corresponding to several resistor types were constructed with fine winding wire on varnish-coated ceramic bodies, and winding temperature was measured by a thermocouple placed beneath the ceramic sealing tube. The experiments establish graphical dependencies of maximum winding overheating on dissipated power at ambient temperatures of 20, 85, and 125 degrees Celsius. These results provide practical data for selecting resistor types or operating powers that maintain specified winding temperatures under defined environmental conditions.
Full Text
EXPERIMENTAL STUDY OF THE TEMPERATURE REGIME OF SINGLE-LAYER HERMETICALLY SEALED MICROWIRE RESISTORS
A. M. Kirik, A. S. Lyashikov
(Presented by Professor, Doctor G. I. Fuks)
Hermetically sealed microwire resistors are finding ever wider application in equipment operating under conditions of high humidity and over a wide temperature range, in particular in places with a tropical climate, under arctic conditions, and at high altitudes.
The availability of data on the thermal regime of the resistor winding under various ambient-temperature conditions makes it possible, in designing equipment, to use resistors that ensure a specified thermal regime and, consequently, definite service characteristics.
In the present work, results are given of an experimental study of the dependence of the maximum overheating of the windings of hermetically sealed microwire resistors on the resistor power and the ambient temperature under conditions of natural convection.
Fig. 1.
1 — resistor, 2 — current leads, 3 — resin, 4 — ceramic body.
The study was carried out on models of hermetically sealed microwire resistors, the construction and dimensions of which are shown in Fig. 1 and in Table 1. The difference between the models and the microwire resistors manufactured in accordance with the VTU OTI 539000 consists in the fact that the winding of the resistor models was made not with microwire but with PEMS winding wire $\varnothing 0.05$ mm. The surfaces of the ceramic cylinders of the models were coated with an electrical-insulating varnish in order to give them the same degree of blackness as normalized resistors.
The layout of the experimental setup and the method for investigating the thermal regime of sealed and unsealed resistors [1] are analogous. The difference is that, in the experiments with sealed resistors, the hot junction of the thermocouple was placed on the winding, i.e., under the ceramic sealing tube.
Fig. 2-a.
Fig. 2-b.
Fig. 2-c.
Table 1
| Type of resistor | \(L,\ \mathrm{mm}\) | \(l,\ \mathrm{mm}\) | \(D_{n},\ \mathrm{mm}\) | \(D_{\mathrm{in}},\ \mathrm{mm}\) | \(D,\ \mathrm{mm}\) | \(R,\ \Omega\) |
|---|---|---|---|---|---|---|
| MVS-721 | 61 | 46 | 17 | 13.5 | 8.3 | 2520 |
| MVS-726 | 24 | 17 | 7.5 | 6.0 | 4.4 | 440 |
| MVS-727 | 25 | 10 | 6 | 5.0 | 3.2 | 106 |
The results of the work carried out are presented by the graphs in Fig. 2a, b, c, which reflect the dependence of the maximum overheating
\(\vartheta = t - t_f\) on the resistor power \(P\) at various ambient temperatures \(t_f\) \((t_f = 20;\ 85\ \text{and}\ 125^\circ\mathrm{C})\).
Using the graphs in Fig. 2a, b, c, for given \(P\) and \(t_f\) one can determine the maximum overheating of the winding \(\vartheta\) (and its temperature \(t\)) for the given type of resistor, or select a resistor that ensures the specified operating regime in terms of \(P\) and \(\vartheta\) under definite ambient conditions \(t_f\).
The results presented may be recommended for practical use.
Literature
A. M. Kirik and A. S. Lyalikov. Experimental study of the temperature regime of single-layer varnish-protected unsealed microwire resistors. The present collection.