Allison Goldin

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  1. 3 Shaft Grounding Alternatives to Help Protect VFDs

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    As the demand for automation and energy efficiency increases, many facility managers, building owners, and engineers are switching to variable frequency drives (VFDs). These solutions are among today’s most sustainable technologies, enabling motors to function at reduced speeds without sacrificing torque. VFDs ultimately work to reduce power consumption in electric motors, saving at least 30% in energy costs. At the same time, VFDs often need more protection than other systems.

    3 Shaft Grounding Alternatives to Help P 1

    Common-mode currents induced by VFDs may cause electrical discharge machining (EDM) that can damage electric motor bearings, shortening their service life and compromising the system’s reliability. Many rotational machines like pumps, generators, and motors use shaft grounding rings to mitigate this issue. These rings allow for easier grounding of electrical currents that would otherwise build up on the machine’s rotating shafts, preventing subsequent fluting and pitting on the bearings’ raceways.

    The grounding ring channels electrical currents along a ring and brush, redirecting them away from the bearings. In theory, shaft grounding rings effectively reduce voltages, but only until they are contaminated by grease or dust. In addition, the rings don’t reduce the damaging currents—they only divert them to the ground grid, where these currents create electrical EMI issues with any electronic device, such as relays and sensors connected to the same electrical grid.

    Although grounding rings may help protect motors from damage, there are some other alternatives available, but only one that is the most effective: Nanotech common mode choke cores.

    Alternatives to Grounding Rings

    The alternatives to grounding rings include shielded cables, insulated bearings, and common mode chokes. Unfortunately, shielded cables and insulated bearings have their own pitfalls as with the grounding ring, leaving the common mode core choke as the best alternative to solving common mode current issues.

    Shielded Cables

    One alternative to grounding rings is to run shielded cables from the VFD to the motor. The shielded cable acts as a Faraday cage, effectively isolating the VFD and motor from the external environment by providing a direct ground path back to the VFD. Unfortunately, the shielded cable is usually not connected properly, which negates the shielding on the cable. In addition, shielded cables add an extremely high cost to the VFD/motor system. In instances where standard cables are buried beneath the floor, replacement is usually not an option.

    Insulated Bearings

    Another alternative to grounding rings is to install ceramic insulated bearings, which form a high-impedance electrical barrier for damaging electrical currents, protecting bearings and motors.

    As with grounding rings and shielded cables, there are many problems associated with insulated bearings. First is the cost. These bearings cost significantly more than traditional bearings, and they still require maintenance and must be replaced periodically. Secondly, the insulated bearing does nothing to reduce the common mode currents. It only traps the motor’s common mode currents, allowing them to circulate and cause excessive heating in the windings. Finally, the common mode currents can eventually overcome the insulation within the bearing and destroy the bearing.

    Common Mode Chokes

    The most effective alternative to shaft grounding rings is Nanotech common mode chokes. By installing Nanotech common mode chokes around the VFD’s output conductors to the motor, the damaging high-frequency common mode current is absorbed in the source of the noise (VFD’s IGBT/SiC/GaN switching) well before the damaging currents reach the motor. As with the other solutions, these common currents are absorbed instead of redirected or blocked.

    Advantages of Nanotech Common Mode Chokes

    There are several advantages to using Nanotech common mode chokes over traditional alternatives. Some of the most notable advantages include:

    • Improved Performance: Nanotech common mode chokes provide superior filtering performance, reducing EMI and improving signal quality. In addition, Nanotech common mode chokes are the only solution that reduces conducted and radiated EMI interference that affects relays, sensors, and other electronic devices connected to the electrical grid. This becomes extremely important when unshielded cables are used.
    • Installation: Installation can be done in less than an hour, eliminating long downtimes associated with the other alternatives.
    • Higher Reliability: Nanotech common mode chokes are a permanent, no-maintenance lifetime solution, unlike all the other alternatives. Because they do not rely on physical contact with the shaft, common mode chokes are less susceptible to wear and tear and can provide longer service life.
    • Cost-Effective: Common mode chokes are typically less expensive than traditional grounding rings, making them a cost-effective solution for improving system performance.

    Why treat an electrical problem with a mechanical device when the electrical solution of Nanotech Common Mode Chokes is readily available?

    Innovative Nanotech Cores From MH&W

    You can prevent common mode currents from causing damage or interference to your VFDs, allowing for efficient and cost-effective operation. Choose Nanotech to reduce electrical noise and ensure your high-power inverter systems continue working as they should. Contact MH&W for more information.

  2. 5 Tips for Reducing Electromagnetic Interference (EMI) in VFDs

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    5 Tips for Reducing Electromagnetic Interference (EMI) in VFD's

    Variable frequency drives (VFDs) are widely used in industrial applications to control the speed, start-up, and torque requirements of electric motors. However, VFDs can produce electromagnetic interference (EMI) that can cause problems with other electronic equipment in the vicinity.

    Electromagnetic interference, called EMI, is unwanted electrical noise that prevents electronic systems from performing as intended. EMI occurs when an electromagnetic field causes disruptions in the radio frequency spectrum of a communication, analog, or digital electronic system. Since EMI can cause devices to operate poorly and, in some cases, to stop working completely, learning how to reduce electromagnetic interference is very important.

    As industry experts with over 50 years of experience, MH&W International Corp. offers reliable solutions for reducing electromagnetic interference in variable-frequency drive systems (VFDs). While our choke products provide a simple and cost-effective method of eliminating high-frequency noise, there are other steps you can take to reduce EMI.

    Here are five tips for reducing EMI in VFDs:

    • Proper grounding: Proper grounding is essential for reducing EMI. Ensure that the system’s VFD and all other electrical equipment are properly grounded according to local codes and standards. One of the first steps to reduce EMI is to properly ground the VFD and other components. Since high-frequency EMI travels on a conductor’s surface, selecting a braided conductor provides increased surface area and a lower resistance path for noise to travel to the ground. Instead of using a solid conductor, consider a multi-strand option.
    • Shielding: Shielding can help reduce EMI from VFDs. Use shielded cables for power and signal connections and ensure the shields are grounded properly.
    • Proper wiring: Proper wiring can reduce EMI. Keep the wiring as short as possible and avoid running it parallel to other wiring or metal surfaces. Use twisted pair wiring for control signals. Shielded cables effectively minimize the effect of capacitively coupled EMI between two cables that run parallel to one another. To accomplish this, the shielding must be grounded only at one point: at the noise source or the panel. However, for high-frequency noises above 1 MHz, it’s better to ground the shield at both ends. This method is also applicable to analog cables. High-power DC voltage cables, motor cables, and other lines should be spaced out by at least eight inches when placed parallel to prevent high-frequency couplings. Taking this precaution will be very helpful in preventing signals from coupling with one another and generating noise.
    • Filtering: Filtering can help reduce EMI. Install filters on the input and output of the VFD to suppress the high-frequency noise. If EMI generation is unavoidable, the next best step is mitigating it at the source or preventing it from entering the system. To achieve this, mount AC line filters on either the grounded frames or the backplane during the design phase. This will prevent EMI from entering the system.

    Since input line side cables also produce noise, minimize it by routing input power cables as far as possible from output power cables and other cables in the circuit. Additionally, the AC power’s length should be reduced, and the filter should be properly grounded and installed near the source of EMI.

    • Distance: Increasing the distance between the VFD and other electronic equipment can also help reduce EMI. If possible, locate the VFD in a separate enclosure or room.

    Install Nanotech® Cores at the Inverter Output

    Out of all the previously discussed methods for reducing EMI, proper wiring is the most effective method; if combined with Nanotech® cores, it is the most simple and effective solution. MH&W Nanotech® products are common mode toroidal cores made with nanocrystalline material that eliminates high-frequency noise at the source.

    Our Nanotech® cores are so effective that unshielded cables can replace shielded cables, reducing the system’s overall cost. Other key benefits of Nanotech® cores include:

    • Effectively reduces radiated emissions
    • Maintenance-free
    • Long service life
    • Easy to install and compatible with existing drive setups
    • Highly effective in drive systems with long cable runs

    The Nanotech®’s magnetic core captures and absorbs high-frequency currents, eliminating unwanted noise. These products are very beneficial in conducted or radiated EMI applications and unlike filters, Nanotech® cores have no passive elements, resulting in low losses.

    Why Choose MH&W

    Reducing electromagnetic interference is critical for any type of VFD. While there are many steps you can take to protect your equipment, installing Nanotech® cores is the most effective and long-lasting solution. MH&W specializes in providing innovative technology for VFD motor installations. Our products are used globally by major OEM VFD manufacturers and end users to ensure their equipment properly functions.

    With engineering and sales operations throughout the U.S., Mexico, and Canada, MH&W International supports the power supply and telecommunications industries with thermal interface materials, powder cores, and other products and services that promote our customers’ long-term goals.

    MH&W International is a leading supplier of magnetic components with over 55 years of experience in the industry. Here are some reasons why you may choose MH&W:

    • Quality: MH&W only sources materials and components from reputable manufacturers to ensure consistent product quality. We also have rigorous quality control processes to ensure that all products meet or exceed customer expectations.
    • Technical expertise: MH&W has a team of experienced engineers knowledgeable in magnetic materials and their applications. We can provide technical support to customers and help them select the best products.
    • Customization: MH&W offers customization services to tailor standard products to customers’ requirements. We can modify products such as cores to meet unique specifications.
    • Global reach: MH&W has a global reach, with sales and distribution centers in North America, Europe, and Asia. This allows us to serve customers worldwide and provide local support in different regions.
    • Competitive pricing: MH&W strives to offer competitive pricing while maintaining high-quality standards. We have long-standing relationships with our suppliers, allowing them to negotiate favorable pricing for our customers.

    Overall, MH&W is a reliable supplier of magnetic components with a strong commitment to quality, technical expertise, customization, global reach, and competitive pricing.

    We offer a comprehensive range of choke products, including:

    To permanently resolve your EMI and VFD motor problems, contact our team today.