Background and Current System Issues: A gantry crane is composed of cranes and hoists, and the power supply for its AC motor drive usually comes from the DC BUS to increase the power usage efficiency. During operation the speed of the cranes and hoists changes rapidly and constantly, and so does the power usage. The unstable electricity may cause a large amount of harmonics, resulting in severe damage to the reactive compensation capacity. Once the reactive compensation capacity is damaged, it may fail to compensate current normally, and the power voltage would fluctuate severely as well. With unstable power and harmonic pollution, the gantry crane system may easily breakdown, threatening the power system and safety of the harbor.
Delta’s Solution: Delta’s gantry crane solution adopts Delta’s SVG2000 Series static var generator to perform highly efficient power compensation and to decrease harmonics. The SVG2000 Series is able to effectively solve the power issues and increase the stability and safety of the gantry crane system.
The features of the SVG2000 Series include:
- Compensates both leading and lagging reactive current and improves PF to 0.99
- Adopts Delta’s power supply module, power voltage range 200-480 V, 525-690 V
- Modular design includes fan module, power module, drive module, control module and power resistor module
- Adopts 7” TFT LCD 65536 full color HMI
- Power capacity: 300kVAR/500kVAR
Benefits:
- After introducing Delta’s SVG2000 Series, the gantry crane system’s THD remains ≦5%, and the PF improves up to 0.95. The power issues of the gantry crane system are solved, and the system can last up to ten years.
- According to field tests, the PF in the original gantry crane system is only 0.34 (far from the standard of 0.9); the system’s power efficiency is low, whereas power consumption is high, meaning the company is likely to be fined by the electric company, which in China is usually 5% of the total electricity fee for every 0.1 below the standard PF of 0.9. What’s more, the THD of the gantry crane system may reach 117.5%, showing severe harmonics pollution in this system, which may possibly cause abnormal equipment operation, or even an electrical fire.
- Delta’s SVG2000 Series solution successfully raises the gantry crane systems’ PF to 0.99, which is higher than the standard PF 0.9, and the THD dramatically drops to only 4.9%, which is much lower than the original system’s 117.5%. Delta’s gantry crane solution effectively improves power efficiency and power quality, reduces power consumption and avoids harmonic pollution, helping customers create an energy-saving and safe working environment and avoid electric company fines.
Specifications
Original System without SVG2000 Series – PF：0.2, Current THD：117.5%
Low Power Efficiency, High Power Consumption, Severe Harmonic Pollution
Delta’s Solution with SVG2000 Series – PF：0.99, Current THD：4.9%
High Power Efficiency, Low Power Consumption, Low Harmonic Pollution
Success Story
- Background：
With an import/export volume of 62.7 million tons and 13 million twenty-two foot equivalent unit (TEU) containers exported in 2010, the Harbor is one of the biggest harbors for coal transportation in China and is now the biggest transportation harbor in the world. The gantry crane system adopted by the Harbor requires highly stable and energy-saving operation. - Delta’s Solution：
To fulfill the Harbor’s gantry cranes’ requirements, Delta’s product development team and professional system integrators studied and developed a specific solution for the customer in 2013 using the AFE Series high-voltage power active front end. The AFE Series has been successfully applied to the Harbor’s gantry crane system with 280kW regenerative power converted and supplied—higher than the standard 200kW. - Benefits：
For Delta’s gantry crane solution, Delta’s AFE Series adopts an LCL filter to reduce harmonics and to assure the power regeneration rate reaches over 30%. The AFE Series has regeneration braking and resistance braking functions and can switch to either mode according to real usage. It also adds a DC contactor at the connection point with the DC BUS; both ensure the system operates stably and safely. - After months of operation, Delta’s solution continues to offer outstanding power regeneration and power quality improvement, providing a highly efficient, energy-saving and stable system for the customer. The satisfied customer demanded that more of Delta’s gantry crane solutions be applied to the Harbor’s gantry cranes.
