CASE STUDY: smart temperature control
22 April 2022
A smart power controller's name says it all: a microprocessor and sophisticated programming make it smart. And it controls power using sensors that monitor voltage and current. Eric Rios explores why smart power control is vital in heating applications.
There are many types of power switches that are used in commercial and industrial applications. Mechanical relays and contactors are ideal for applications where they are not switched very often because they are relatively inexpensive and do not produce much heat. But for precise control of electric heating, these switch types are a poor choice because they wear out and fail quickly if switched frequently. In this instance, smart power controllers are a sensible choice.
Being able to control the output based on the measurement of power delivered to the load improves temperature control performance because it compensates for line voltage fluctuations or even partial load failures faster. This means that there is significantly less deviation from the temperature set point than would occur with the same temperature controller paired with a traditional solid-state power switching product.
The temperature controller and power controller work together. The temperature controller measures the temperature with a sensor and determines how much of the available power is necessary to achieve set point. The power controller interprets the output from the temperature controller and controls the delivered power accordingly. Finally, the power controller adjusts the power delivered for voltage fluctuations and to the best of its ability when there is a partial failure of the heater.
Process and equipment characterisation
The smart power controller measures the line voltage and the current through the load. With that information it calculates the load resistance and how much power is being delivered by the heater. Equipment manufacturers can use this information during commissioning to identify if there is a problem. For example, abnormally high resistance could indicate a poor connection that might eventually cause a premature failure or even a fire if not corrected.
For instance, power controllers can help companies monitor the load parameters during equipment installation and compare the profile with previous known good start-ups. By doing this, they can receive warning of issues localized to the heated zone, allowing preventative action to be taken before a failure occurs.
End users can similarly monitor these parameters overtime and correlate them to good and bad production results.
Integrating a smart power controller with other automation equipment allows process variables to be monitored remotely and allows operators and line maintenance personnel to quickly locate problems.
Consider this example, from a Watlow customer. A manufacturer of power transmission cables once relied on employees to periodically check the current gauges visually for each zone of extruders that coat the cables. On shifts with lower staffing, faulty product was often the first indication of a problem. The customer replaced the solid-state power controllers in the extruders with the Aspyre DT power controllers from Watlow, so they could determine if cable needed to be scrapped or whether production could continue until the scheduled maintenance.
Watlow’s range of heating equipment, including its Aspyre controllers, is frequently used by heavy duty industrial companies in petrochemicals, heat treatment and power generation. The Aspyre model is available between a range of 35 to 2,100 amps to support a wide variety of applications. For example, a single high amp Aspyre unit is ideal for applications using multiple small units with low range amps.
Overall, the smart features and functionality of smart power controllers enables users to minimize scrap and unscheduled down time — improving operations and output.
Eric Rios is product manager for controls at industrial technology company Watlow
Aspyre is a registered trademark®