Design of High Speed 2 Pole Synchronous Compressor Motor – China Natural Gas Pipelines

PPI Engineering

ABOUT:

CNPC is China’s largest oil and gas pipeline contractor and operator. CNPC owns and operates pipeline networks and storage systems covering 29 provinces, municipalities and autonomous regions as well as Hong Kong SAR in China.

By the end of 2014, their oil and gas pipelines in China totaled 79,054 kilometers in length, including 18,132 kilometers for crude oil, 50,836 kilometers for natural gas and 10,086 kilometers for refined products, accounting for nearly 70%, 78% and 47% of the nation’s total, respectively.

REASON FOR PROJECT & CHALLENGES:

CNPC needed a motor with an operating speed from 3120 – 6600 rpm, where constant torque would be up to 6000 rpm, and constant power from 6000 – 6600 rpm.

Motor specifications:
Frame size: BT75.110 2W
Standard: IEC60034
Poles: 2
Shaft Output: 20 000 kW
Stator Winding: 2 x 3 phase star connected winding displaced 30deg apart with start points unconnected.
Motor Supply: 2 x 6 pulse Load Commutated Converter (6 phase output in total) 2 x 4800V line voltage (2771 V phase) and 2 x 1383.4 A displaced 30 deg elec. Apart 22952 kVA,20657 kW at 0.9 pf, 100 Hz (6000 rpm) IC81W Cooling with 32 degC water inlet temp.
Enclosure: IP55
Mounting: IM6010
Ex-Protection: ||2GEEExp||B T4

The motor needed to be powered by a load commutated inverter [LCI] which has inherent harmonics, this made the motor electromagnetic design very challenging compared to a fixed 3600 – 1500 rpm speed sinusoidal supply synchronous motor.

In addition, another challenge was the need to model the increased magnetic losses for operation points above 3600 rpm.


HOW PPI HELPED:

PPI conducted research in terms of modelling the electromagnetics of the motor including the harmonic power losses supplied by the LCI.

Various in-house modelling software was used and developed during this project. Please refer to software catalogue for descriptions.

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