6 Special device functions
76 2011-07-01/00561073 [SCR Power Controller TYA202]
value. This damps out any tendency to overshoot the final temperature.
Other applications for U
2
control are:
- In lighting systems: In this case, the intensity of the illumination is
proportional to U
2
.
- Some resistance materials have a TC that is close to 1. These include
heating elements made from nickel /chrome, constantan etc. This does not
place any special demands on the SCR power controller (e. g. current
limiting). The resistance characteristic for a heating element with a TC » 1 is
shown in Figure 2.
Figure 2: Heating element with TC » 1
I
2
control Current control (I
2
control) is advantageous for heating elements with a
negative TC, where the electrical resistance becomes smaller as the
temperature increases (Figure 3).
This behavior is shown by non-metallic materials such as graphite or glass
melts. Molten glass is not usually heated by heating elements but by letting a
current flow through the melt, so that the electrical energy is converted directly
into heat in the molten material. The current is applied through electrodes.
Figure 3: Heating element with a negative TC
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