What are the key elements for medium voltage drive selection?

When selecting a medium voltage (MV) drive, there are several key elements to consider to ensure optimal performance, reliability and cost-effectiveness.

Commercial Considerations

When making purchasing decisions, it is important to look beyond technical specifications and consider commercial factors. Reliability and cost are key considerations. High reliability is crucial, especially when MV drives are used in critical applications. To ensure you are getting a reliable product, consider the manufacturer’s reputation and look at the drive’s MTBF (Mean Time Between Failure) value. It’s important to note that while a high calculated MTBF value is desirable, comparing MTBF values from different manufacturers may not be a straightforward comparison because the methods of calculation can differ.

When considering cost, it’s essential to evaluate not just the initial purchase price but the lifecycle costs as well. Lifecycle costs include installation and commissioning, training, energy consumption, reliability, maintenance, spare parts, after-sales support and disposal. While MV drives can have a higher upfront cost than low voltage drives, they are energy efficient and have longer lifespans. Payback times of 12-18 months are typical, but can be shorter depending on the application and duty cycle.

Technical Considerations

Beyond commercial considerations, there are several technical factors to consider. Efficiency is a major benefit of MV drives. Efficiency levels of 97% can be achieved with MV drives, including the input isolation transformer. When assessing efficiency, it’s important to consider the total drive system efficiency, not just the efficiency of the converter. The energy savings achieved with an MV drive can be substantial enough to pay for the drive in a few months.

Another key consideration is the layout, specifically the amount of space the drive will occupy. Some industries, like petrochemicals, have limited space and high costs per square foot, making a smaller footprint desirable. Some modern MV drives achieve a small footprint through compact design and a flexible input transformer configuration. This configuration allows the transformer to be placed outside the electrical room.

Technology is another important element. The technology platforms for all variable speed drives are constantly changing. Refer to relevant sources for up-to-date information on motor control platforms and power semiconductor technology.

Finally, performance is a crucial aspect of drive selection. A key performance criterion is process control, which is significantly enhanced by variable speed drives.

When considering MV drive selection, it’s essential to carefully evaluate both commercial and technical factors to ensure you select a drive that meets your specific application needs and delivers optimal performance and value over its lifetime.

We can support your decision-making process by providing expert, independent advice and assistance on AC or DC-drive applications for the following tasks:

• Develop the project plan presentation.
• Define and manage the requirements for the Power Drive System (PDS).
• Evaluate the composition and components of the Power Drive System.
• Organize and coordinate internal and external pre-bid meetings.
• Prepare and issue invitations to bid in collaboration with Engineering, Procurement, and Contracting compagnies and/or vendors.
• Assess preferred manufacturers for transformers, inverters, and motors.
• Review offers and verify compliance with your PDS specifications.
• Assist in the selection of vendors for transformers, variable frequency drives, and motors.
• Clarify any outstanding issues related to your PDS.
• Define requirements and test plans for both witnessed and non-witnessed Factory Acceptance Tests (FAT).
• Establish requirements for Site Acceptance Tests (SAT).
• Validate the on-site execution of Site Acceptance Tests for the components of your Power Drive System (PDS).