Based on the customer’s tender requirements and leveraging our company’s technological strengths, we are providing users with a complete high-voltage variable frequency drive (VFD) system solution. This solution is centered around the VFD itself, complemented by a customer-supplied power-frequency bypass section, a motor selection switching mechanism, and an on-site power monitoring system.

Power supply section: The grid incoming line is 35 kV, and the outgoing line is 10 kV, with a capacity of 16,000 kVA.

Frequency conversion section: This is the core of the entire system and adopts a modular cascaded architecture. It ensures reliable heat dissipation for each module, which features an innovatively designed heat-pipe radiator. This type of heat-pipe radiator significantly increases the heat-dissipating surface area per unit, thereby guaranteeing effective cooling even under full-load or overload conditions.

Bypass section: This section switches the load from variable-frequency drive operation to line-frequency drive operation. QF1 and QF3 are equipped with comprehensive motor protection devices, ensuring reliable motor protection under line-frequency conditions. A long-term test of full-load operation at line frequency can save customers 288 kWh per hour, thereby reducing testing costs.

Switching section and on-site power monitoring section: Based on their specific requirements, customers can select the type of load to be driven. Since it is necessary to monitor the current and power of the M2 load when operating at 6 kV or 6.6 kV, a dedicated power monitoring section has been added here.

After receiving our proposal, Apollo assembled a team of industry experts to validate its feasibility and requested that we provide on-site technical clarifications regarding the proposal. More than a dozen experts from the client’s side raised numerous specialized questions about the project requirements and the system design. Our team members provided detailed explanations and systematic analyses, offering the client satisfactory answers. Given the unique nature of the nuclear power industry—where expert panel acceptance cannot be scheduled at any time—we were required to ensure that our frequency converters could be delivered within three months in order to expedite the pump testing and obtain early acceptance.

The company has established a green channel for this project, covering all stages—from procurement and SMT to production and various types of testing—and is giving top priority to this project. Thanks to the concerted efforts of all departments within the company, we were able to notify the customer’s factory on time to complete the corresponding acceptance procedures for the product.

The two main projects have received very high satisfaction from the client:

1) The inverter operates at full current, and the temperature rise of each unit meets the customer’s requirements.

2) During seamless switching, the switching current exhibits no noticeable fluctuations, achieving true seamless switching.

Inverter System Diagram

The first task undertaken by the Xindashida high-voltage frequency converter marked the acceptance of China’s first set of auxiliary feedwater pumps.

The equipment has arrived on site, and the civil construction work has already been completed. The installation, wiring, and high-voltage electrical connections of the equipment were all carried out on schedule. The project has now entered the final critical commissioning phase. The first task assigned to the entire system is the installation of the first auxiliary feedwater steam-driven pump unit—a set of equipment with China’s own intellectual property rights. This project is one of the client company’s key annual projects. The test plan consists of two phases: static testing and dynamic testing. The so-called static testing involves powering all equipment in the system with low-voltage control power but not with high-voltage power, thereby verifying the correctness of the system’s logic for all parameters under static conditions. In the dynamic testing phase, with a load applied, we will evaluate the mechanical and electrical performance of each component.

Starting from static debugging, both the customer’s technical personnel and our own technicians meticulously checked every signal and every detail, carefully verifying the operational status of data from all auxiliary equipment. During the high-voltage dynamic testing, on-site staff conducted real-time monitoring of critical parameters such as the inverter’s instantaneous current and power, as well as the pump’s pressure and temperature rise. Through variable-frequency drive speed regulation tests, we collected relevant data under different pressure conditions. The entire pump unit test ran late into the night, yet the process went extremely smoothly. The parameter readings obtained from the inverter’s monitoring largely matched those measured by the customer’s precision instruments. The customer expressed full recognition of the inverter’s outstanding performance.

On July 2, 2014, Shanghai Apollo Machinery Co., Ltd. successfully completed the acceptance testing of the first auxiliary feedwater pump unit with China’s own intellectual property rights. This product fills a domestic gap and is of great significance in promoting the localization and self-reliance of critical core equipment for China’s nuclear power plants, completely breaking the monopoly held by foreign manufacturers.

High-Voltage Inverter Room

After successfully completing the first mission, the high-voltage frequency converter has now completed numerous additional test tasks. The head of mechanical engineering at Apollo informed us that the main feedwater pump unit will undergo testing during the Golden Week holiday. This project is the largest one Apollo Mechanical has undertaken in the past two years and represents a critical milestone—a significant technological breakthrough crucial to the localization of China’s nuclear power industry. Given the unique nature of the nuclear power sector, if the testing phase cannot be completed on schedule and pass the required certification, the project will have to be postponed until next year, resulting in immeasurable losses. We sincerely hope that our technical staff can join in the pump testing. Upon learning of this situation, company leadership attached great importance to it and instructed the project team to select and dispatch key technical personnel to actively support Apollo Mechanical’s testing efforts for this project.

The main pump unit consists of two pumps: one is a feedwater pre-pump, and the other is the main feedwater pump at the pressure stage. During actual operation, these two pumps are mounted side by side on a single motor, with the total power of one pump exceeding 12,000 kW. According to the pump test group’s requirements, the two pumps were first tested separately. The parameters of each pump were measured and meticulously recorded. After the pumps were combined, their total output power exceeded the rated power of the frequency converter; therefore, for long-term operation, it was necessary to switch to mains-frequency operation. Once the pump unit was brought down to operate at 50 Hz, all pipelines and water pressures had stabilized within normal ranges, and the tested power had already surpassed the rated power. Using the host computer system provided by our company, we issued a seamless switching command. Within one second, the frequency converter locked onto the grid’s phase and voltage, then issued a bypass command, successfully transferring the load to mains-frequency operation. At the moment of switching, the pump’s pressure gauge and flow meter showed virtually no fluctuations whatsoever.

At 23:32 on October 17, 2014, a historic moment arrived when Shanghai Apollo Machinery Co., Ltd. successfully completed the hot-state test and thermal shock test of its main feedwater pump unit, as certified by a panel of experts from the nuclear power industry on-site. This type of destructive testing is a world first for any pump manufacturer internationally.

On November 1, 2014, entrusted by the National Energy Administration, the China Machinery Industry Federation hosted in Shanghai a verification meeting for the prototype joint commissioning test and test loop system of the main feedwater pump unit for a million-kilowatt-class nuclear power plant—Shanghai Apollo Machinery Co., Ltd. The project successfully passed the verification!

Through our collaboration with Apollo Machinery Co., Ltd., we’ve gained a deep understanding that all industries are striving to create “Made in China” innovations with independent intellectual property rights. As a high-tech enterprise receiving key national support, Xindashida regards the revitalization of national industries as its own responsibility. We are committed to independent innovation and technological breakthroughs in the fields of electrical drives and motion control, launching a series of high-quality products and technologies that boast independent intellectual property rights, thereby contributing to the advancement of “Made in China.”

Current during inverter startup and switching