The Reliance VFD: Basics of Variable-Frequency Drives

Close up image of a GV3000 Reliance VFD SE Drive.
20 HP Variable Frequency GV3000/SE Drive from Reliance Electric

Reliance VFD drives have been around for years. VFDs have been widely used for industrial applications, for good reason. Pulse-width modulation (PWM) VFDs offer low costs, high efficiency, and excellent input power factor.

However, VFDs need proper care and installation to run optimally. Sometimes this means controlling airflow going to the drive to control heat generation. VFDs have a typical efficiency rating between 95-98%. But VFDs produce more heat than other electrical equipment, especially when enclosed. And heat losses are directly related to the VFD’s efficiency rating.

Make sure to note your drive’s max operating temperature under real operating conditions. Some drives can operate to 122 degrees Fahrenheit safely. Others can only withstand max temps of 104 degrees Fahrenheit before overheating. To extend the life of your equipment, err on the side of caution and try to operate VFDs below their rated max operating temperature. This will extend your equipment’s lifespan. It will also reduce any risk of localized overheating.

Positioning is Key

One way to ensure your Reliance VFD maintains temperature is through proper positioning. Try to place VFDs close to the bottom of electrical enclosures. This will ensure incoming air is as cool as possible, since it hasn’t already run across other components. Also, maintain recommended right-to-left clearances between units.

Why Are VFDs Used?

Many prefer VFDs like the Reliance VFD over single-speed drives because they can control the speed of an AC motor while offering smooth startup capabilities. Adjustments to frequency delivered to the motor prevents straining from heavy load.

VFD Design Saves Energy

This same frequency adjustment offers energy savings, too. VFDs allow motors to operate at less than full speed. A 25% reduction of motor speed can decrease energy consumption by close to 60%. Meanwhile, a 50% reduction can decrease consumption by almost 90%.

It is important to note “frequency adjustment” can also fall under the misnomer of “speed control.” Speed control is the result of the former. As downward adjustments in frequency occur, other improvements follow improved energy consumption. Mechanical stress lowers, extending machine lifetime. Noise levels also reduce.

Where are VFDs Used?

Three out of every four VFDs produced end up as part of control systems for pumps, fans, and compressors. It is easier to control the speed of a pump through a VFD rather than try to control the flow of water or air in the system through valves. This makes VFDs perfect for pump and fan applications.

Need replacement parts for your Reliance VFD? We can help! Talk to our team today.

Motors and Drives: Typical Repairs

Close up image of a repair in process.  Motors and drives sometime need repairs.
Sometimes repairs are needed. We can help.

At AX Control we do a lot of repairs on motors and drives.  Not only do we offer repair services for our customers, but we also examine every reconditioned part leaving our warehouse for defects and optimize its performance before it gets boxed up for transit.  Our people get plenty of hands-on time with all sorts of drives and motors. 

Skilled technicians take care of all our repair work. We back up that work with a 2-year warranty for AC/DC and Servo Drives, and a one-year warranty for Motors.  

But do you know what may lead to your components needing repair?  We get there’s a lot to know about industrial automation equipment. We thought we would offer up a list of the most common causes we’ve noticed, partitioned by type of drive or motor.  

AC Drives

There have been many technological advances in the field of AC Drives that have brought more features to these drives even as they’ve decreased in size and cost.  

AC Drive from Reliance Electric
The 15V4150 Reliance GV3000 15 HP AC Drive is one AC drive in our stock.

The primary driver of repairs in AC Drives, without a doubt,  is heat.   This may come from various sources, but when you get to the root of the problem heat is the cause of the damage.  

Here are a few of the most common ways heat strikes: 

  • A dusty environment.  When fans aren’t cleaned on a regular basis, the drive can’t pull air through, and heat builds up.  Protection is easy: maintain a regular maintenance schedule and keep fans and other heat dissipating equipment clean.  Try to cut down on the amount of dust in your environment through mitigation. 
  • Power spikes.  These can come from other machines, from lightning strikes, or from your main power line.   You can often limit these problems by adding a line reactor in front of your drive system to protect from transients and power surges. 
  • Too much power draw.  If a drive is attached to a poorly-maintained motor, such as one with ungreased bearings, too much bearing wear, or shaft imbalance, this can cause a mechanical overload that increases the motor’s demand on the drive.  Connected systems have to be maintained together or they will die together. 
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