US 11,752,835 B2
Operating method for an electric heater
Najim Belkaid, Mulhouse (FR); Guillaume Daudon, La Bourgonce (FR); and Jean-Francois Walter, Turckheim (FR)
Assigned to Mahle International GmbH
Filed by Mahle International GmbH, Stuttgart (DE)
Filed on Dec. 20, 2019, as Appl. No. 16/724,171.
Claims priority of application No. 18215432 (EP), filed on Dec. 21, 2018.
Prior Publication US 2020/0198441 A1, Jun. 25, 2020
Int. Cl. B60H 1/22 (2006.01); F24D 13/02 (2006.01); F24D 19/10 (2006.01); H05B 3/22 (2006.01)
CPC B60H 1/2227 (2019.05) [F24D 13/024 (2013.01); F24D 19/1096 (2013.01); H05B 3/22 (2013.01); B60H 2001/2265 (2013.01)] 19 Claims
OG exemplary drawing
 
1. 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, the operating method comprising:
heating a fluid passing the electric heater to an outlet temperature by the at least one heating element;
operating the electric heater in one of a normal mode, in which the at least one heating element is supplied with at least one of a direct current and a direct voltage, or a protection mode, in which electrical power supplied to the at least one heating element is regulated by pulse width modulation;
wherein the control unit compares the reference temperature with the critical temperature;
wherein the electric heater is operated in the normal mode if the reference temperature is less than or equal to the critical temperature;
wherein the electric heater is operated in the protection mode if the reference temperature is greater than the critical temperature; and
wherein the critical temperature includes a temperature at which the heating element changes from the negative temperature coefficient mode to the positive temperature coefficient mode.