Abstract: The invention relates to a method for determining an output temperature of a fluid after flowing through a PTC heater with a PTC heating element. In the method a current of the PTC heating element, a supply voltage of the PTC heating element and a duty cycle of the supply voltage are determined, and the output temperature of the fluid is calculated based on the current (I), the supply voltage and the duty cycle (PWM). The invention also relates to a PTC heater for carrying out the method.

Abstract: An operating method for an electric heater may include heating a fluid passing the electric heater to an outlet temperature by at least one heating element and operating the electric heater in one of a normal mode or a protection mode. In the normal mode, the at least one heating element may be supplied with at least one of a direct current and a direct voltage. In the protection mode, electrical power supplied to the at least one heating element may be regulated by pulse width modulation. The electric heater may be operated in the normal mode if a reference temperature is less than or equal to a critical temperature and in the protection mode if the reference temperature is greater than the critical temperature.

Abstract: A method for regulating a heater including at least one heating element having a temperature-dependent electrical resistance is disclosed. The method may include determining, with a regulating unit of the heater, a current heating behaviour of the heating element based on a time profile of the resistance of the heating element. The heating element may exhibit (i) an NTC heating behaviour at temperatures below a transition temperature, (ii) a PTC heating behaviour at temperatures above the transition temperature, and (iii) a transition between the NTC heating behaviour and the PTC heating behaviour at the transition temperature and a resistance minimum. The method may further include determining, with the regulating unit, at least one input parameter for the heating element based on the current heating behaviour. The method may also include regulating, with the regulating unit, the heating element via the at least one input parameter.

Abstract: An operating method for an electric heater having at least one control unit with at least one temperature sensor measuring a reference temperature, and at least one heating element having a positive temperature coefficient mode above a critical temperature and a negative temperature coefficient mode below the critical temperature, may include heating a fluid passing the electric heater to an outlet temperature by the at least one heating element, and operating the electric heater in one of a normal mode or a protection mode. In the normal mode, the at least one heating element may be supplied with at least one of a direct current and a direct voltage. In the protection mode, electrical power supplied to the at least one heating element may be regulated by pulse width modulation. The electric heater may be operated in the normal mode if the reference temperature is less than or equal to the critical temperature, and in the protection mode if the reference temperature is greater than the critical temperature.