Picking a variable frequency drive is where many buyers get burned — cheap units fail within days, while imported brands bring heavy repair bills and long lead times. This article explains what really matters when choosing a VFD: reliability, after-sales support, and a manufacturer that stands behind its product. It breaks down TAGOL, a 20-year self-developed and self-manufactured VFD maker and a national high-tech enterprise. With an automated production line that lowers failure rates, every drive passes a 48-hour high-temperature aging test and is re-inspected before shipment, backed by an 18-month warranty plus 24-hour technical and installation support. It also answers the five questions buyers most often hesitate over when purchasing a VFD.

This bilingual technical article introduces variable frequency drives (VFDs), an industrial device for AC motor speed control. It details the VFD’s internal parts including the rectifier, DC bus, inverter and control circuit, as well as auxiliary cooling and protection components.

The paper explains the functions of main‑circuit and control terminals, together with standard wiring specifications, such as correct power‑and‑motor terminal connection, grounding requirements and anti‑interference cabling rules. It also provides frequently‑asked practical engineering questions.

Aimed at field engineers, this material offers practical guidance for VFD installation, commissioning and safe operation.