Modern Medium Voltage Drives can be found running in all kinds of environments. At EMA, we’ve seen a variety of drives installed in a variety of places; from Water Treatment, to Cement, to Mining, to Manufacturing, the list goes on and on. Despite being very reliable pieces of equipment, MV drives do fail (we make a living off of it), and certain environmental conditions can rapidly increase the failure rate of your medium voltage drive. You could be killing your drive without even knowing it!
Be Cool Man:
Medium Voltage drives utilize several switching components such as diodes and transistors that produce a significant amount of heat. A 1000 HP, 4160V drive produces between 20 and 25 KW of heat when fully loaded, which would be enough to heat most of our homes! The heat sink, cooling fans, and filters are designed to remove the heat from the drive’s components in order to keep it cool; however, if the ambient temperature and/or the environment isn’t conducive to that, you’re not only in danger of tripping on overheat, but you’re also shortening its life.
Drives running in harsh environments is inevitable in some situations. A cement plant is naturally going to have cement dust in the air and a manufacturing plant will naturally have dirt on the floor, there is no way around it but by properly performing preventative maintenance, you can greatly increase its ability to cool itself.
Rules To Live By:
In VFD maintenance, we have 4 rules: Keep it clean, Keep it tight, Keep it cool, and Keep it dry. Other than tightness, 3 of the 4 rules involve the environment the drive is in. It never ceases to amaze me when the most simple rules of maintenance are not followed by a plant that depends on a medium voltage VFD for production, losing thousands, if not hundreds of thousands of dollars every hour it is down. Dust, Dirt, and Oil can and will sit on large and small, board-level heatsinks, greatly reducing the effectiveness of heat dissipation, thus reducing the useable life of your drive.
Killing Me Softly:
There is a general rule of thumb that says “Every 10 degrees rise in C, manifests itself in half-life of electronic components”; while this might not always be absolutely true (see article here), it is universally known that heat is bad for electronics. Even if you are not running your drives hot enough to trip on overheat, the better it can be cooled, the longer you can expect to keep them running. Electrolytic capacitors, which make up the DC bus of many medium voltage variable frequency drives, are especially susceptible to heat. Hotter temperatures, as well as humidity can rapidly accelerate electrolytic capacitor failure, which leads to expensive repairs on your drive.
Do The Little Things:
At EMA, we HIGHLY recommend a comprehensive Preventative Maintenance program on all of your Medium Voltage VFDs, and we’d love to help you with that. BUT even if you don’t use us, doing a few small things that allow your drive to stay cool will greatly decrease your chance of failure:
- Vacuum the enclosure
- This will get rid of most of the standing dust and dirt that gets clogged in the heat sink and cooling fans
- Clean or replace all cabinet filters
- Typically, the filters are designed to be cleaned with soap and water or replaced. We have many customers that replace the filters with disposable filter media and change it every quarter.
- Check Cooling Fans
- Cooling fans are often overlooked even though they’re the primary device in which most drives cool themselves. Are all of them running? Are the bearings worn? Bad cooling fans can become a big problem when they’re not working properly.
- Keep An Eye On Ambient Temperature
- Most VFDs are rated to operate at a maximum of 40 degrees Celsius. The drive could have the best cooling fans ever, but if the air it is circulating is too hot, they will not be able to do their job. Unless de-rated, a medium voltage VFD must be in a conditioned space that allows it properly circulate cool air. We had a situation not too long ago where the air conditioner in the electrical room stopped working. Even though the drive cooling fans were working fine, the temperature rapidly increased and the drive was in danger of faulting. Side Note: We monitor the ambient temperature 24/7 in a drive with our DriveScan remote monitoring tool. Reach out to us for more information.
Don’t Be A Killer:
Are you slowly killing your medium voltage drive? By removing dust, dirt, and other containments, you can greatly increase the life of your drive by allowing it to properly cool itself. Want some help! Let EMA do it for you! We perform comprehensive preventative maintenance on medium voltage drives every day! Give us a call, contact us via email, or click the chat to discuss getting PMs on your drives today! Let us prove to you that No One, ANYWHERE, Is Better At Drives Than We Are!
One Response
What a great article. The thermal balance of drives in general is essential for reliable operation. I have listed some helpful tips below:
Air-cooled drives usually dissipate heat directly into the room and require additional measures to evacuate the critical heat losses out of the room or E-house.
Look for a solution where losses are ducted outside the room, possibly combined with air conditioning of the room. Care should be taken to avoid creating a vacuum or wind tunnel effect in the room. The data provided by the E-house supplier for the range of supply air and exhaust air is to be considered when designing the container cooling system. Appropriate air guidance measures must be implemented to prevent air short-circuits in the container.
If a central exhaust air system is utilized, it is essential to verify that the pressure drop necessary for converter cooling is maintained.
Air cooling your drive in a heavily contaminated atmosphere will be challenging. Closed-loop solutions such as air-to-air exchangers provide a higher degree of contamination protection thanks to the two separate airflow designs, which keep dirt, moisture, and other elements from getting into the equipment.
An air-to-water heat exchanger will offer similar benefits if a water-cooling system is available.
In the case of water-cooled drives, most of the losses are ejected into the water; less than 10% of the losses are rejected into the room. Clearly, the water-cooled drive should have its own treated water closed circuit, with pump(s), tank, and heat exchangers for cooling the treated water. Eventually, special attention to water fouling of the external water-cooling system is required.