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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.

Electric Motor Failures: How to Diagnose

Small DC Motor rotor showing windings — File:Small DC Motor Rotor.JPG” by Jjmontero9 is licensed with CC BY-SA 3.0.

When your electric motor fails, it can be difficult to know why. But there are quick tests you can use to easily diagnose problems.

Make sure to disconnect power from your electric motor before beginning. Power is not required. This step protects you and the equipment.

Motor Identification

Electric motors have a metal nameplate or tag riveted to the outside of the motor housing. This nameplate usually includes a lot of useful information, including

Nameplate for a Reliance Electric Servo Motor

Manufacturer Name. Who made the motor.
Serial Number or Model Number. The model number tells you the make of your motor. The serial number uniquely identifies it.
RPM. Revolutions Per Minute. The output capability of your motor.
Horsepower. A rating of motor performance.
Voltage. The motor’s voltage requirements.
Current. How many amps the motor requires.
Frame Style. The unit’s physical dimensions.
Type. This can include NEMA ratings, cooling indications, etc.

A wiring diagram may also be included on the nameplate. In some cases, this tag will include the unit’s manual identification number, too.

The Most Important Factor When Choosing a Motor Drive

Close up of a Reliance Electric GV3000 Motor Drive — A motor drive can run on DC power, or use AC power like the 15V4150 GV3000 Drive from Reliance.

There are several things to consider when sourcing a drive to use with a motor. These include

Function. What will the components be doing? Make sure to choose drives and motors designed for the same purpose.
Location. Industrial components are specifically designed to hold up to the more rigorous demands of the factory floor. Some products may be rated for outdoor use while others might be restricted to inside locations only.
Compatibility. Unless you need a conversation-starting paperweight, an incompatible drive is worthless.
Cost. What’s your budget? Hint: this is where reconditioned and surplus products really shine. They’re often a fraction of the cost of new.

While all of these factors are important and should be a part of your decision-making process, none of them make the top of the list.

So what does?

Current and Voltage.

Always be sure as you look at drives that their output voltage meets the input voltage rating of your motor.

Also, be sure the drive’s output current rating meets or exceeds the FLA (full load amperes) rating of the motor. You can typically find the FLA on the motor’s nameplate data.

If you have more questions about sourcing the correct motor–or any other product–for your needs, contact our team today.