Chilldown Electrical System for S-IVB Space Vehicle

This paper presents the electrical system used to drive the chilldown motor pumps on the S-IVB space vehicle. This system consists of a 56 volt battery supplying power to the two three-phase solid state inverters which in turn drive two cryogenic motor pumps. Included in this paper is a short description of the overall chilldown system requirements. The advantages of the a-c system over the d-c system are discussed with emphasis on weight and reliability. Two functionally identical 1.5kva inverters were designed. One inverter uses germanium transistors in the output stage while the other uses silicon transistors. Both inverters were designed to have a quasi-square wave output. The inverter circuitry is described and the advantages of each is discussed including a comparison of weight, size, operating temperature, efficiency and voltage rating.