how to define your motor inside your drive train

Prioritize safety when operating your mission-critical machine with Medium Voltage drives.

The plant owner is responsible for safety of the operating personnel and all persons in his responsibility area.
No need to say that medium voltage equipment is connected to a high-power supply grid. It becomes imperative to recognize that even a malfunctioning component, insulating material failure, or environmental contaminants like conductive dust can lead to serious consequences, including electric shock, overheating, or catastrophic failures such as explosions. Diligent oversight and proactive measures to mitigate such risks in mission-critical applications are required.

Ensuring Safety in Medium Voltage Drives

With safety as one of your top priority in medium voltage drives, you need to consider several key factors to protect both personnel and equipment:

  • Implement common safety practices, such as training programs, lock out/tag out procedures, and employee awareness campaigns.
  • Use Arc-Resistant Enclosures: Choose drives with arc-resistant enclosures to redirect arc flash energy away from personnel.
  • Ensure Proper Interlocks: Install high-voltage compartment doors with interlocks to prevent them from opening when power is on or being energized when the door is open. A mechanical interlock helps you safely isolate high-voltage sections of the drive. The drive should include a method to lock-out and tag for safe access for maintenance or troubleshooting.
  • Ensure Compliance with Safety Standards: You must verify that your MV drives complies with relevant safety standards such as IEC, UL, and CSA. Always verify that the equipment is tested and certified accordingly. Check for certifications from recognised bodies.
  • Implement Functional Safety Features: Opt for drives with built-in functional safety options. For example, Safe Torque Off (STO) allows you to remove power from the motor without disconnecting the variable speed drive from the grid, reducing accident risks and enabling a quick system restart after reaching a safe state.
  • Provide Ground Fault Protection: Your drive must include ground fault protection during starting, acceleration, running, and deceleration. The best approach is monitoring leakage current in a high-impedance ground circuit.
  • Minimize Fault Currents: Choose a drive designed to minimize fault currents and arc flash potential. This can be accomplished with drive topologies M2C and 2L SC HB using distributed DC energy storage and localizing faults to individual power cells. Also provide undervoltage protection to prevent operational instability.
  • Ensure Proper Grounding: Follow the manufacturer’s grounding recommendations. The protective earth conductor must have adequate conductivity and an appropriately selected cross-sectional area to meet safety regulations. Properly shield and ground your cables.
  • Integrate an Emergency Stop: Your drive system should include an emergency stop button that integrates into a broader safety protection concept, allowing you to shut down operations immediately if needed.
  • Prioritize Isolation: Use isolation transformers in your drive design, as transformerless designs are more vulnerable to misoperation, lightning strikes, and line voltage surges.
  • Protect the Motor: Your drive should protect the motor from damage caused by short circuits, overloads, and internal power component failures.
  • Manage Harmonics Effectively: Ensure your drive produces near-sinusoidal current waveforms and avoid causing misoperation or overload in other equipment.
  • Use Proper Safety Labels: Clearly label areas with medium or high voltage using appropriate warnings to alert personnel to potential hazards.
  • Environmental considerations: Note whether there are specific environmental requirements at the installation site such as corrosive gases or conductive dust which would influence which design is appropriate
  • Torsional analysis is important for safety reasons when using medium voltage drives, especially in applications with wide speed ranges or potential for transient events. While modern VFDs generally produce acceptably low torsional shaft stresses, analysis is still important, particularly for LCI (Load Commutated Inverter)-type VFD.

Conclusion

By implementing these safety measures, you can ensure a secure and reliable working environment when operating and maintaining medium voltage drives. Proactively addressing these risks helps you protect both personnel and equipment while maintaining compliance with industry standards.

In all cases above we would be glad to assist you. All it takes is that you contact us for a free consultation.
Further down the road, we will enable informed decision-making by offering you our independent advice and support for  following tasks:

    • Setting up the project plan presentation.
    • Definition of the requirements of the power drive system.
    • Evaluation of the composition of the power drive system (PDS).
    • Internal and external pre-bid meetings.
    • Setting up the invitation to bid to vfd and motor manufacturers and EPC’s.
    • Screening of preferred vendors.
    • Verification quotation and exceptions VS your specifications and requirements.
    • Order clarification of the composition of your power control system.
    • Factory acceptance tests (FAT) requirements of your power drive system.
    • Witnessed and non-witnessed factory acceptance tests.
    • Site acceptance tests requirements.
    • Validation of the site acceptance tests (SAT) for your power drive system.

    Glossary

      Here is a glossary of technical terms used in our page and their relevance to safety in medium voltage drives::

      • Arc Flash: A dangerous electrical discharge that can cause severe burns and other injuries. It is mentioned that medium voltage drives should redirect arc flash energy away from personnel.
      • Emergency Stop: A critical safety feature that allows for the immediate shutdown of operations when needed. Drive systems should include an emergency stop button integrated into a broader safety protection concept.
      • Functional Safety: Built-in safety features in drives, such as Safe Torque Off (STO), that help to reduce accident risks. STO allows for the removal of power from the motor without disconnecting the variable speed drive from the grid.
      • Ground Fault Protection: A protection mechanism in drives that detects and responds to ground faults during starting, acceleration, running, and deceleration. The best approach is monitoring leakage current in a high-impedance ground circuit.
      • Harmonics: Electrical disturbances that can cause misoperation or overload in other equipment. Drives should produce near-sinusoidal current waveforms to manage harmonics effectively.
      • High-Voltage Compartment Doors with Interlocks: Safety measures to prevent access to energized parts. These interlocks prevent the doors from opening when power is on, or being energized when the door is open.
      • Isolation Transformer: A type of transformer used in drive designs to provide electrical isolation and protection against misoperation, lightning strikes, and line voltage surges.
      • LCI (Load Commutated Inverter): A cusrrent source type of inverter used for very large power applications producing quite some torque pulsations.
      • Lock-out and Tag-out Procedures: Safety practices that are implemented to ensure that equipment is de-energized and locked to prevent accidental operation during maintenance.
      • Medium Voltage Drives (MV Drives): Electrical equipment operating at voltage levels above 1000V, and that present specific safety challenges due to their connection to high-power supply grids.
      • Motor Protection: Measures taken by the drive to protect the motor from damage caused by short circuits, overloads, and internal power component failures.
      • Protective Earth Conductor: A grounding conductor that must have adequate conductivity and a properly selected cross-sectional area to meet safety regulations.
      • Safe Torque Off (STO): A functional safety option that removes power from the motor without disconnecting the drive from the grid, reducing accident risks and enabling quick system restarts.
      • Safety Standards: Compliance with standards such as IEC, UL, and CSA is required, and equipment should be tested and certified accordingly.
      • Torsional Analysis is important for safety reasons when using medium voltage drives, especially in applications with wide speed ranges or potential for transient events.
      • Undervoltage Protection: A protection mechanism that prevents operational instability.

      Get Your DRIVE Expert Guidance Today

      Get in touch for practical solutions and independent expert advice tailored to your power drive system needs. Rest assured that your critical machines are driven reliably, efficiently and safely.