在高温气冷堆氦气透平和发电机之间布置减速箱，作用是将氦气透平的高转速降低到发电机转子所需要的额定转速。本文介绍了由一对高速齿轮、低速齿轮啮合传动组成的一级圆柱齿轮减速方案。方案的优点是结构简单、制造方便、运行可靠性高；缺点是设备体积大、输出和输入不同心。该减速箱方案避免了在能量转换单元中使用大功率变频器和高速电机，节约了制造成本，但同时在系统中引入了润滑油系统，增加了一定的风险。

In a High Temperature Gas-cooled Reactor (HTGR) system, the gearbox is installed between Helium turbine and dynamotor, to reduce the high speed of gas turbine to a normal speed required by dynamotor rotor. Single reduction cylindrical gearbox is used with a pair of gears for high speed and normal speed regulations, respectively. The scheme is simple in structure, easy for manufacture and with high reliability. The disadvantage of such a scheme is the heaviness, and with the input and output centers being at different positions. In the gearbox, high speed electric generator and high power transducer can be avoided, to reduce the investment, instead by using a lubricant box, which increases the risk of HTGR Helium gas turbine system.