Power source is insensitive to load changes

摘要

For the heating and cooling elements common in industrial systems, resistance is not a fixed quantity. These elements include such devices as positive-temperature-co-efficient heaters and thermoelectric coolers. Their resistance can change more than 100% during operation, and the result is a change in power dissipation for elements receiving drive from a fixed voltage or current source. Worse, excessive power can damage the heating or the cooling element. Driving the element with a fixed and regulated power driver overcomes these problems (Figure 1).