| 摘要 |
PURPOSE:To prevent generation of a contact spark in a switching means and flowing of a rush current by switching an inverter equipment and a commercial power from one to another at a zero-crossing point at the time of switching between said inverter equipment and commercial power. CONSTITUTION:A commercial zero-crossing detection means 10 and an inverter zero phase output means 15 are provided in an apparatus. Then, when an inverter zero-position output means 15 is compared with the commercial zero-crossing detection means 10 and both means coincide with each other, a switching means 3 is converted from an inverter equipment side to a commercial power side. Therefore, when operation is switched from a commercial power to an inverter equipment, a compressor motor is never shifted to a regenerative mode even if the output frequency of said inverter equipment varies, an electric current can be controlled to a small quantity, and reliability and cost can be reduced. |
