Motor control equipment is heavily challenged in marine and offshore applications. Motors for ships, offshore platforms and port facilities generally operate in conditions of humidity, salt mist, vibration, unpredictable power supply and restricted installation space. Because of these conditions, dependable starting, stable operation and good motor protection are extremely necessary.
VFDs and soft starts are two viable motor control options for equipment such as pumps, fans, compressors, ballast pumps and cooling water pumps. In general a VFD is used if you need speed regulation and energy conservation. A soft starter is used if you want to lower the starting current and mechanical impact only.
1. Motor Starting Challenges in Marine and Offshore Systems
Large motors can have considerable inrush current when started directly. This can create voltage drops, disrupt the power system and increase mechanical stress on motors, couplings, pumps and other driven equipment.
These challenges can be more problematic in marine and offshore situations where the power system may be more sensitive and the equipment is typically harder to repair. Hence, controlled motor starting is a significant approach to improve system reliability and prevent unnecessary wear.
2. When to Use a VFD
A VFD allows for smooth start and variable speed control. It is appropriate for applications where the motor speed has to be adapted to the real need of operation such as flow control, pressure control or energy-saving operation.
RENLE RNHV series medium voltage VFD is appropriate for fan, pump and compressor. It supports medium voltage system like 6kV and 10kV. It contributes to decreasing wasteful energy usage by modifying motor speed , enhancing flow and pressure management , and enabling more stable system operation .
The RNHV series also has low voltage ride through, flying start, torque limiting, unit bypass and remote monitoring functions. These qualities are appropriate for industrial and offshore applications which require better reliability.
For motors that run at a constant speed yet require a smoother start, a soft starter is a feasible solution. But instead of providing full voltage right away, it slowly increases motor voltage throughout startup. This reduces the beginning current and the shock to the mechanism.
The RENLE RNMV line of medium voltage solid-state soft starters are appropriate for medium voltage squirrel-cage motors. It offers voltage ramp start and current limiting start to lessen electrical effect and mechanical wear of the motor starter.
The RNMV series additionally offers protection functionalities like as overload, overcurrent, undervoltage, phase loss, stall, overheat and long-start-time protection. It is well suited for pumps, compressors, conveyors and other fixed speed motor applications in maritime and offshore systems.
4. How to Choose Between a VFD and a Soft Starter
Choosing between a VFD and a soft starter is not only about product type, but also about how the motor operates in real working conditions. For marine and offshore applications, users should consider whether the equipment needs speed regulation, energy saving, smooth starting, or constant-speed operation.
Choose Based on Operating Requirements
The choice between a VFD and a soft starter depends on the actual operating needs of the equipment.
VFDs for Speed Control and Energy Saving
VFDs are ideal for equipment that requires speed control, energy saving, or precise adjustment of flow and pressure.
Soft Starters for Constant-Speed Operation
Soft starters are more economical and practical when the equipment only needs smooth starting and then runs at a constant speed. In marine and offshore applications, VFDs and soft starters can also be used together to balance performance, cost and reliability.
