Category: 2022 News

HEAT DISSIPATION FROM VARIABLE FREQUENCY DRIVES (VFD’S)

Variable Frequency Drives (VFDs) have become a standard part of control panels. Since their development years ago, because of their efficiency, consider their contribution toward the electrical enclosure’s heat load.

Many VFD manufacturers and suppliers sometimes publish power dissipation or efficiency information in brochures.

The efficiency of most VFDs is between 93 to 98 percent, and loses the balance of the energy as heat.

Despite their high efficiency, VFDs generate a significant amount of heat. Unless removing the heat through enclosure cooling, the drives can overheat and trip, causing plant outages.

The power dissipated is calculated by subtracting the efficiency from 100 percent and multiplying the result by the drive’s power consumption.

Estimating the heat loss of a 95 percent efficient, 100 horsepower drive as 5 percent of 100 horsepower equals 5 horsepower or 3729 watts.

Although a 5% estimate for engineering purposes is ordinarily acceptable if a safety factor adds to other losses, obtaining the VFD drive efficiency at the design load from the equipment supplier is much better.

It would help if you also considered the thermal losses from other ancillary equipment, such as DC phrase-shifting transformers, power supplies, and switchgear which may or may not be significant.

The losses from a transformer could be an additional 4 percent of power consumption.

Again, obtaining these figures would generally be from the equipment suppliers.

HEAT DISSIPATION FROM VARIABLE FREQUENCY DRIVES (VFD’S)

If the drive uses braking resistors and is frequently stopped and started, dissipating the power by the braking resistor should also be considered.

Varian Frequency Drive manufacturers specify a maximum allowable operating temperature for their products. In some cases, it is relatively low as it allows for the heating effect of power electronics on the circuit boards inside the drives.

Some manufacturers also de-rate their drives above temperatures of 104 ºF. (40 º C)

Thus it is good engineering practice to design the enclosure cooling for a temperature below the equipment’s maximum temperature to promote long life and minimize the possibility of overheating.

The total enclosure heat load is the total heat dissipation of all equipment items, plus the heat transfer through the enclosure walls. Due to the ambient temperature, local heat sources, and solar radiation. This is true even though there are various ways of calculating this number.

The most effective method is to use an online heat load calculator like the Nex Flow® Panel Cooler Calculator. This will help to address obtaining the heat load.

The heat load is usually the greatest on startup. They are making vortex coolers like the Nex Flow® Panel Cooler popular for VFD cooling because, on average, they only need to operate about 30% of the time.

Because they operate on compressed air, the energy cost is relatively low. And it is often offset by the elimination of filters, dealing with condensate. Also, other factors, such as labor cost for maintenance, as they are essentially maintenance-free.

Flexibility with Manifold blow-off and cooling systems

Nex Flow supplies manifolds adapted to compressed air amplification products such as Engineered Air Nozzles, Air Jets, Air Edger® flat jet nozzles, and Air Amplifiers. 

They are for blow-off, cleaning, drying, and even cooling applications.

They allow for a much more convenient installation for the customer when using several products is needed.

Where standard versions are not suitable, producing special manifolds—this approach of needing spacing products for the particular application. Making unique manifold shapes can be a special order.

Also, varying the standard systems offered allows for many variations.

For example, we are interchanging parts rather than all air nozzles or all Air Edgers. 

And have a variety of blow-off or cooling units such that. 

For example, one long manifold can address several lines with different devices for different purposes.

Also, adding attachments is possible.

We also directly attach swivels to individual items on the manifold so one nozzle. For example, we point one way, another in a different direction, etc.

Do you need to extend a blowing device?

Adding extensions can be beneficial.

There is great flexibility in using these different accessories with the needed device using compressed air.

Using the original designs by Nex Flow remain popular and are called Vintage Manifolds, which are compact but limited to eight (8) outlets.

Flexibility with Manifold blow-off and cooling systems

However, using the X Stream Manifolds (LINK) more often because they are heavy-duty and have up to 12 outlets. However, we are manufacturing more extended versions for customers.

Standard material is either anodized aluminum or stainless steel.

Designing one system for light blow-off but primarily for cooling incorporates the FX20 X-Stream Fixed Air Amplifier. Installing various combinations is easy. 

It allows cooling items such as castings and other more significant areas requiring rapid cooling.

Installing a blow-off station for cleaning, drying, or cooling, consider the Manifold System a convenient, reliable, and flexible method for efficiently accomplishing the task.

It is changing the engineered amplification devices as needed. And adding accessories for directing the air to where it is required should the application be altered.

When to use Point Of Use Separators for Filtration of Compressed Air

Compressed air filtration domination continues using compressed air filters with membranes, removing moisture, oil particles, dirt, and debris.

Various products have entered the market in an attempt to replace pint of use filters. The compressed air is spun at a high velocity by separating the loose moisture, oil, dirt, and debris. Thus, collecting these contaminants and then having them settle and then removed.

These systems are very successful but only to a certain particle size level. Because the smaller the size, the less the mass and the more difficult to “spin” and settle out and remove.

Large separators utilizing this principle have been around for years. They are used extensively after air compressors to remove a large chunk of loose moisture. This happens before entering the air delivery system.

But eventually, the idea of smaller designs came into being to address serious moisture problems. This happens particularly at the point of use.

There are several designs on the market, and Nex Flow® offers one as well (The Nex Flow® Super Separator)

Different manufacturers have varying designs, patenting some are spinning the air to remove moisture. And some are tested to ISO 12500 to determine the maximum particle size guaranteed. Designs and sizes will vary, but the principle remains: spinning to remove moisture, debris, and oil.

However, the best guarantee we could find that such designs offer in particle size is 1 micron which may or may not be acceptable for the factory process.

For example, designing typical oil removal filters to remove particles down to 0.3 microns, so one should be dubious of claims to remove oil contamination with such separators.

When to use Point Of Use Separators for Filtration of Compressed Air

Where the units are used best where there is a very high replacement of filter (membrane) cartridges, 

Because of moisture and other (larger than 1 micron) contaminants. Due to some problem in the supply or delivery of the compressed air to the point of use. And when the monitoring and maintenance cost of existing point-of-use filters becomes excessive in material cost as well as time and labor.

Nex Flow® typically recommends installing still (or maintaining any existing) filters downstream of the Super Separator.

This way, the separator will do the heavy work by removing excess moisture and more significant dirt and debris, and the other membrane filters will catch the rest.

From experience, if the downstream filters had excessive maintenance or replacement before using the separator. There should be a dramatic improvement in the life of the cartridge by a factor of about five times in most cases but around three times if the problem is primarily oil droplets.

That increased life still makes using the point-of-use separator economical in complicated compressed air delivery systems.

Some claims have circulated that these separators can sometimes replace compressed air driers. Still, that would be highly situational as driers draw out from the compressed air or cool and remove moisture that condenses. 

These separators can only remove moisture suspended in the compressed air already.

Such claims depend on the reason the drier was there originally.

But regardless, such point-of-use separators can be an ideal solution to excess moisture, oil, and dirt issues in compressed air systems.

Reason for static Control static can cause several problems in a production facility.

In the film, extrusion for static can cause edges to curl and jam machinery.

In injection molding, the problem tends to be the attraction of dirt caused by static charge onto the part. Thus, creating painting and packaging issues.

Today there are many ways to eliminate the static buildup on parts. More powerful AC static bars and DC systems that can work farther away from the target product eliminating static charge. Neither requires any air.

Small packaged blower systems with air can assist in static control for very slow-moving production. Because introducing blower air, tends to be turbulent. The “ions,” pushing further, also re-combine. Especially as the distance grows if the target moves too fast,. There is insufficient time to eliminate the static simply because the ion concentration weakens.

Using the laminar flow of a compressed air-operated air knife or an annular air amplifier will push the “ions,.” Their re-combination will slow, but it still will weaken over distance.

So it should be with great caution when you come across claims of removing static from a target many feet away. Specifically when no time frame is specified, as the time needed can be quite long.

Even a static bar with no air behind it, several feet from a highly charged target, will still remove the static “given enough time” – again, a long time.

And in any production line, that exposure time is severely limited for obvious reasons.

Reason for Static Control With Air Suggested Products

The real reason for using high-pressure blowers with a static bar or compressed air-operated air knives like the Nex Flow® Ion Air Blade Ionizers and the Ion Blaster Beam® is cleaning.

If the distance is significantly considerable from the target or the static charge is exceptionally high on the target, the only way to remove the static and clean the part of dust and debris in a production line is to use a fixed bar or pin ionizer strong enough.

Providing a firm Ion Pin with their Ion Blaster Beam being mounted to a plastic attachment. By avoiding grounding, which can weaken the static elimination pin.  

They have a standard and an extra strong static bar (which produces more ions for static elimination when dealing with a fast-moving and highly charged target) with their Ion Air Blade Ionizers.

When considering static elimination, try to avoid using air, especially if the purpose is solely for removing static charge, even if you cannot get close to the target.

But if cleaning is necessary, then an air source,, will be required with the static-eliminating device.

But do not get fooled that air alone, no matter what the source, will extend the range of the static eliminating “ions” without weakening the effect, thereby extending the time necessary for exposure to remove the static charge.

The only effective way to ensure static removal is cleaning from a distance. With a stronger concentration of static elimination ions.

Nex Flow offers additional consultation in using air with static and can advise on the optimal solution for your facility.