Heating Current Measuring

• It shows, independent of the number of phases, the current presently flowing through the heater.

• It provides information on the heater's condition (total fail, partial fail, if heaters in parallel) and monitors current data considering a tolerance band.

• It monitors power actuator conditions and reports an alarm for continuously running heating output (e.g. permanently short circuit SSR's), which can cause damage from overheating.

• It supports a number of controller functions. For example, bad adjustments of control parameters can be avoided because the identification function (auto tuning) is only started if a corresponding heating current is recognized in the control zone, i.e. when it is certain that the zone is ready for heating. Else, the starting of the identification function is delayed until a heating current is recognized. Hence, a wrongful adaptation is prevented without user input or additional software.

Every PSG controller, respectively every PSG control system is prepared for heating current measuring. The heating current is measured over so-called current transformer modules that are available in different variants. Depending on the controller or control system these are available in two modes.

Measuring Method

Single Current Measuring: A separate measuring input is available for each control zone; the wiring for the heating of a single control zone is lead through a current transformer. This measuring method is used for dynamic control processes, for example for hot runner control.

Summation Current Measuring: The control wires for the heaters of several control zones are run through a current transformer. This function is run through the controller software or via the IO group through direct output control. This measuring method is used for non-dynamic control processes, for example for extruder temperature control.

Compensation of Power Grid Interference

In order to reduce the impact of power grid variance on the measured heating current, modules that measure the mains voltage are available to calculate a correction of heating current.