Fig. 1.
The measurement system that enables thermographic measurement of the temperature of the relay package Tpcam. A – tripod, C – screw, E – thermographic camera, R – observed relay, d – distance between package and thermographic camera lens.
Fig. 2.
Measuring system that enables relay control. K1 – tested relay, R1, R2 – load, P1 – button.
Fig. 3.
Measuring system used to force a specific number of relay switching cycles. P2 – button controlled by an Arduino Uno microcontroller.
Fig. 4.
Three-dimensional model of the tested relay.
Table 1.
Summary of the materials assigned to individual components of the relay model and their corresponding thermal conductivity coefficients λ.
| Part of the relay | Material | λ [W/m∙K] |
|---|---|---|
| Coil | Copper | 385 |
| Contact | Copper | 385 |
| Case | Plastics | 0.22 |
| Leads | Aluminum | 204 |
Table 2.
The values of coefficients elam, eturb, flam, and fturb.
| Shape | Gr ⋅ Pr | elam | eturb | elam | eturb |
|---|---|---|---|---|---|
| Vertical flat wall | 109 | 0.59 | 0.129 | 0.25 | 0.33 |
| Upper flat wall | 108 | 0.54 | 0.14 | 0.25 | 0.33 |
| Lower flat wall | 105 | 0.25 | NA | 0.25 | NA |
Table 3.
Edge size of the mesh element and the corresponding simulation time and simulation accuracy. The values of ΔTcs represent the largest recorded differences in the determined contact temperatures Tcs among the five simulations.
| No. | Mesh element edge [mm]length | Simulation [s]time | ΔTcs [K] |
|---|---|---|---|
| 1 | 2.0 | 16 | 2.5 |
| 2 | 1.0 | 64 | 0.8 |
| 3 | 0.7 | 175 | 0.2 |
| 4 | 0.5 | 473 | 0.1 |
| 5 | 0.2 | 3 139 | 0.1 |
Fig. 5.
The obtained model with the applied mesh and the point at which the package temperature was determined.
Table 4.
The obtained values of the contact temperature Tcs (from simulation), package temperature Tps (from simulation), and the temperatures Tct (contact temperature measured with the thermocouple) and Tpt (package temperature measured with the thermocouple).
| No. | Tcs [K] | Tct [K] | Tps [K] | Tpt [K] |
|---|---|---|---|---|
| 1 | 293.1 | 293.2 | 292.7 | 293.2 |
| 2 | 294.2 | 294.2 | 293.5 | 293.2 |
| 3 | 297.3 | 297.2 | 294.7 | 294.2 |
| 4 | 302.6 | 301.2 | 298.4 | 297.2 |
| 5 | 306.8 | 305.2 | 300.1 | 299.2 |
| 6 | 312.8 | 312.2 | 302.1 | 301.2 |
| 7 | 321.5 | 320.2 | 307.3 | 305.2 |
| 8 | 333.8 | 332.2 | 315.1 | 314.2 |
| 9 | 341.0 | 339.2 | 322.1 | 320.2 |
Table 5.
Measurement results for seven successive relay operating cycles with a pause time of 500 ms between ON/OFF switching operations.
| No. | Tpcam [K] | Tpt [K] | Tps [K] | Tcs [K] |
|---|---|---|---|---|
| 1 | 302.1 | 302.15 | 302.5 | 310.9 |
| 2 | 306.3 | 306.15 | 306.6 | 318.3 |
| 3 | 309.0 | 309.15 | 309.1 | 322.7 |
| 4 | 311.2 | 311.15 | 310.8 | 325.8 |
| 5 | 309.6 | 310.15 | 309.4 | 323.3 |
| 6 | 312.4 | 312.15 | 312.7 | 329.2 |
| 7 | 314.0 | 314.15 | 314.1 | 331.7 |
Table 6.
Measurement results for seven successive relay operating cycles with a pause time of 300 ms between ON/OFF switching operations.
| No. | Tpcam [K] | Tpt [K] | Tps [K] | Tcs [K] |
|---|---|---|---|---|
| 1 | 301.7 | 301.15 | 301.5 | 309.1 |
| 2 | 307.5 | 307.15 | 307.3 | 319.5 |
| 3 | 312.9 | 312.15 | 312.6 | 329.0 |
| 4 | 315.8 | 316.15 | 315.4 | 334.0 |
| 5 | 317.9 | 318.15 | 317.3 | 337.4 |
| 6 | 320.1 | 320.15 | 319.6 | 341.5 |
| 7 | 323.9 | 322.15 | 323.5 | 348.5 |
Table 7.
Measurement results for seven successive relay operating cycles with a pause time of 100 ms between ON/OFF switching operations.
| No. | Tpcam [K] | Tpt [K] | Tps [K] | Tcs [K] |
|---|---|---|---|---|
| 1 | 311.3 | 311.15 | 311.1 | 326.3 |
| 2 | 313.8 | 313.15 | 313.5 | 330.6 |
| 3 | 317.8 | 317.15 | 317.6 | 337.9 |
| 4 | 319.6 | 319.15 | 319.4 | 341.1 |
| 5 | 322.0 | 322.15 | 321.8 | 345.4 |
| 6 | 322.8 | 323.15 | 322.7 | 347.0 |
| 7 | 325.4 | 324.15 | 325.2 | 351.5 |