Electric compressors in which an inverter that converts DC power supplied from a power unit to three-phase AC power and that applies the power to an electric motor via glass-sealed terminals is integrally incorporated is employed as compressors for air conditioners installed in electric cars and hybrid cars. These integrated-inverter electric compressors are generally configured such that an inverter accommodating section (inverter box) is provided on the periphery of a housing that accommodates an electric motor and a compression mechanism, in which the inverter is integrally incorporated.
The inverter includes high-voltage components, such as a common mode coil, a normal mode coil, and a smoothing capacitor (head capacitor) provided on power lines to reduce noise; a power system board on which a switching circuit constituted by semiconductor switching devices, such as IGBTs, is mounted and which converts DC power to three-phase AC power and applies the power to an electric motor; and a control board on which a control and communication circuit constituted by devices that operate at low voltage, such as a CPU, is mounted and which controls AC power to be applied to the electric motor, in which the power system board and the control board are modularized and incorporated in the inverter accommodating section on the periphery of the housing.
To improve the ease of installation in vehicles, it is preferable to reduce the size of integrated-inverter electric compressors, as well as inverters, as much as possible. In such inverters, electrical connections among the inverter module, the smoothing capacitor, the normal mode coil, and the common mode coil are generally made via a busbar assembly in which a plurality of relay busbars are integrated (for example, see Patent Literatures 1 and 2).
Furthermore, Patent Literature 3 discloses an inverter that is made compact by using a thin ceramic capacitor or film capacitor as a smoothing capacitor, accommodating it in an inverter module in which a power system board and a control board are integrated with the use of a module case, and providing a filter capacitor to reduce common mode noise on the base of the module case.