There are inverters in Shijiazhuang. Their company is Ying Da Electronic Technology Co., Ltd., whose main products are frequency converters. We have used two of their products now, and the quality is not bad. They come to the door to install and debug, and also provide technical services. It is said that Shijiazhuang was the first to produce frequency converters. We chose their products for easy installation, after-sale security and convenient maintenance in the future. After all, the electrician in our factory is not professional.