| 摘要 |
<p>To control an inverter, such as to regulate the rotary speed of an AC electro-motor in a sewing machine from a DC supply, the DC voltage is held at a low level until the operating frequency has achieved a given value. As the operating frequency passes above this value, the DC voltage is increased with the operating frequency. Pref. the DC voltage is held where the AC voltage is rectified from the AC supply by a rectifier, and a condensor is charged through a switch. The switch is regulated to harmonise with the operating frequency, and has a high switching frequency at the start of operation. Pref. the DC voltage is switched through an inverter section.</p> |
