Hebei Zhongxiang Energy 20.5 MW Main Compressor Variable-Frequency Soft-Starting Project

Petrochemicals | Coke-Oven-Gas-to-LNG and Liquid Ammonia Plant / Main Compressor | Variable-Frequency Soft Starting for a Large Compressor Motor

Project Background

Hebei Zhongxiang Energy's plant for producing LNG from coke oven gas and liquid ammonia from hydrogen-rich tail gas uses a large main compressor. The main compressor motor is rated at 10 kV and 20.5 MW. The project must address starting and subsequent grid-connected operation of this ultra-high-power motor.

Project Challenges

• Starting a 20.5 MW high-voltage motor demands substantial starting capacity and requires careful control of the impact on the compressor system and power distribution network.
• Soft starting must be followed by reliable transfer to the line-frequency grid supply.
• The plant operates as a continuous process, so the main compressor starting sequence has a significant effect on production stability.

Dayu Solution

A cascaded high-voltage variable frequency soft starter starts the main compressor motor. A software phase-locked bypass function transfers the motor to the line-frequency grid supply once the frequency, phase and voltage conditions are met.

Key Configuration

• Main compressor motor: 10 kV, 20.5 MW.
• Configuration: GBRQ series high-voltage variable frequency soft starter.
• Operating mode: Variable-frequency soft starting, phase-locked synchronization and line-frequency bypass operation.

Application Value

Variable-frequency soft starting and phase-locked bypass enable the main compressor motor to start smoothly and transfer to line-frequency operation, reducing the impact on the compressor system and power distribution network during starting.