Multipassage, multiphase electrical heater

Abstract

A resistor particularly useful as a multiphase, self-regulating fluid heater has passages extending through a body of ceramic resistance material of positive temperature coefficient of resistivity (PTC) for heating fluid adapted to pass therethrough. Several embodiments are provided with electrically conductive coatings formed on inner walls of the passages with the passage walls defining thin webs of the resistance material having uniform thickness from end to end. The passages are arranged in a plurality of sets with the conductive coating on the walls of the passages of each set interconnected and adapted for electrical connection with a respective electrical phase. The passages of the sets are alternated relative to one another throughout the body with a passage of one set immediately adjacent only to passages of other sets. The passages are configured in different embodiments including hexagonal, triangular and rectangular as seen in plan view showing one end of the body. Other embodiments have electrically conductive coatings formed on opposite end faces of the body. In one embodiment the coating on one face serves as a common connection while the coating on the other face is separated into portions electrically isolated form one another with each portion adapted to be electrically connected to a respective phase. The latter embodiment is particularly suited for a wye electrical connection while the former embodiments are well suited for delta connections. In another embodiment, particularly suited for a delta connection, the conductive portions on one face are angularly disposed a selected amount relative to the conductive portions on the other face.