VFD Challenges for Shipboard Electrical Power System Design

3VFD Motor Controller for Ship Service Auxiliaries

The use of variable frequency drive (VFD) motor controllers are gaining popularity in place of across the line starters, soft starters, and reduced voltage starters due to operational advantages. The VFDs are being used on small vessels auxiliary loads such as offshore support vessels. The use of VFD in a small vessel with low power generation and weak distribution bus often creates electrical noise issues such as harmonics, affecting the entire electrical system.

The use of VFD is recommended; however, considerations should be made such as:

1. Do not use VFD in small vessels with weak power generating bus.
2. Do appropriate analysis, and calculations to establish that the VFD‐related THD will be below 5% under all operating conditions.
3. Establish that the use of VFD will have no adverse effects on the electrical system.
4. The VFD‐related internal components should not be grounded at any point. However, if component grounding is necessary, appropriate measures must be taken, so that the circulating current does not create an adverse effect.
5. Do not use neutral grounded low voltage system (grounded WYE).
6. If neutral grounded low voltage system 120 V, three‐phase, four‐wire system is used, the load distribution must be properly balanced so that the neutral current circulation is within allowable limits.
7. The system must be monitored and alarmed if the neutral current circulation is unacceptable.
8. Use proper VFD cable.
9. Use proper VFD cable ...