Variable Frequency Drive Basics

Variable frequency drives are also known as (VFDs), variable speed drives (VSDs), adjustable speed drives, and inverters. Variable frequency drives are solid state controllers used in AC or DC electric motor applications. Most variable frequency drives are applied on alternating current (AC) electric motors in the industrial manufacturing world. There are some direct current (DC) electric motor applications that apply variable frequency drives, but most manufacturers seek AC motors because DC motors are expensive and often fail. Variable frequency drives can also be used as a phase converters when three phase motors need to be operated from single phase power.

Variable frequency drives can be used in small appliances, large mills, lathes, air compressors, conveyors, and many other electric motor applications in the industrial manufacturing world. Over 30 percent of the world’s electrical energy is consumed by electric motors in fixed-speed fan, pump, and air compressor applications. The basic idea for using a variable frequency drive on mills, air compressors, and fans is to reduce the amount of electrical energy being consumed which consequently reduces electricity costs on unused power.

Energy Savings

About 3% of the total installed AC electric motors in the United States use variable frequency drives.An estimated 60-65% of electrical energy in the United States is used to supply electric motors, and 75% of that electrical energy is consumed by fan, pump and air compressor applications.

Approximately 18% of the electrical energy used in the 40 million motors in the United States could save power consumption via efficient energy improvement by using variable frequency drives on these electric motor applications.

Performance and Operation

Variable frequency drives are applied to alternating current (AC) electric motors to increase quality control in manufacturing processes in the industrial manufacturing world. Variable frequency drives increase quality control in the industrial manufacturing world via monitoring the electric motors’ speed, pressure, temperature, torque, and tension.

Fixed-speed electric motor loads subject the electric motor to a high starting torque and electrical current surges that are up to eight times the full-load motor current. When a variable frequency drive is used on an electric motor, the variable frequency drive gradually ramps the electric motor up to full load operating speed, and this decreases mechanical and electrical stress, which minimizes motor maintenance and motor repair costs which ultimately, extends the life of the electric motor and manufacturing equipment.

Variable frequency drives’ unique programming capabilities allow for application specific patterns to minimize electrical and mechanical stress on the electric motors’ they’re operating. Every variable frequency drive manufacturer uses a unique parameter selection designed so that every manufacturing facility can seek out the product designed for their industry.

Repair and Replacement

The internet has brought high demand of quality repair processes and competitive pricing in the industrial manufacturing world.Maintenance technicians began seeking alternative solutions via the internet for their need of variable frequency drive repair and replacement because maintenance technicians do not always receive the services needed to be a leader in their industry.

A highly trained repair facility is the backbone of successful production. Precision Electric has been repairing industrial electronics, rewinding electric motors, and servicing all other industrial-related equipment since 1982. Customers on the coasts of the United States send Precision Electric repair work everyday such as variable frequency drives, servo motors, servo drives, encoders, printed circuit boards, electric motors, and all other related equipment.

Precision Electric offers free quotes for all repair work and has a reputation for keeping manufacturers’ downtime to an absolute minimum while increasing production processes for 30 years. Equipment repaired by Precision Electric is more reliable than brand new equipment purchased from the manufacturer, because Precision Electric uses the most advanced testing equipment and replaces generic components with the best components in the industry. Precision Electric offers an in-service warranty on all repair work completed. The Precision Electric in-service warranty begins the day repaired work is put into service and ends 12 months thereafter.

ABB Variable Frequency Drives

ABB variable frequency drives incorporate advanced drive technology developed by ABB engineers and are capable of tackling the most demanding industrial manufacturing requirements.

ABB manufactures low voltage and medium voltage AC variable frequency drives for all applications in the industrial manufacturing world.ABB variable frequency drives offer specific functionality in all applications. ABB variable frequency drives are designed to control different types of motors and are capable of flexible connectivity to automation networks.

ABB variable frequency drives provide adjustable motor control from basic applications such as pump and fan operations to intricate applications for a wide range of industries, especially process industries such as pulp and paper, metals, mining, cement, power, chemical, oil and gas.

General Purpose Drives

ABB general purpose variable frequency drives include pump, fan and conveyors. ABB general purpose variable frequency drives are logical in situations where there is a need for simple installation, programming, and where custom engineering is not required.

ABB general purpose variable frequency drives are designed for a wide range of applications. ABB general purpose variable frequency drives have simple installation instructions, and are easy to setup and operate. ABB general purpose variable frequency drives provide several built-in features. ABB general purpose variable frequency drives are only available through highly trained, technical partners.

Industry Specific Drives

ABB industry specific variable frequency drives provide customers with drive solutions for HVAC, water, and waste water management operations. ABB has worked closely with HVAC, water and waste water industries to develop specific functions in the ABB industry specific drives to meet optimum operating performances and overall energy reduction in these industries. ABB industry specific drives are complete AC variable frequency drive packages.

Machinery Drives

ABB machinery variable frequency drives offer machinery users component drives and high performance machinery drives.ABB machinery variable frequency drives provide precise speed control of diverse applications from spa bath motors, treadmill motors, and high precision applications such as positioning and synchronization systems.

ABB Drive Repair Services

Precision Electric is a trained partner and distributor of ABB variable frequency drives. Precision Electric is the only certified ABB Start Up facility in the Northern Indiana area. The Precision Electric Certified ABB Start Up Team offers customers an additional 1 year warranty on all ABB variable frequency drives. Many customers of Precision Electric take advantage of these start up services because not many variable frequency drive manufacturers offer a 2 year warranty on their variable frequency drive products. Precision Electric has been repairing ABB variable frequency drives for nearly 20 years. Call Precision Electric today for free repair quotes on ABB variable frequency drives.

Variable Speed Drive Blog

The Precision Electric variable speed drive blog offers information about variable speed drives used in the industrial manufacturing world. The information on the Precision Electric variable speed drive blog comes from hands-on experience made by Precision Electric service technicians. The Precision Electric variable speed drive blog is an excellent source to learn about variable speed drive applications in the industrial manufacturing world.

What Is A Variable Speed Drive?

Variable speed drives are also known as variable frequency drives. Variable frequency drives are solid state motor control systems designed to control the speed of an alternating current (AC) electric motor. Variable frequency drives are often seen in manufacturing facilities across the globe. Variable frequency drives can reduce energy costs by 50% or more, by reducing the AC electric motor speed (RPM) on variable torque applications such as fan and pump motor applications.

When To Replace / Repair A Variable Speed Drive

Maintenance technicians in the industrial manufacturing world send variable speed drives and other related equipment to repair facilities when their equipment fails. Once the repair facility has inspected and determined the cause of failure on the variable speed drive equipment, the repair technician offers a repair and/or replacement quote. When obsolete variable speed drive equipment cannot be economically repaired, variable speed drive repair facilities should offer a solution to retrofit said variable speed drive equipment with new variable speed drive equipment.

Where To Send Variable Speed Drives For Repair

Qualified repair facilities are an asset to industrial manufacturers, so it is important to send failed variable speed drives and other related equipment to a trustworthy repair facility.Precision Electric has repaired thousands of variable speed drives that other repair facilities have determined to be ‘not worth repair’. Precision Electric stands out from their competition by keeping customer’s production to a maximum while minimizing the overall downtime.

Types of Variable Speed Drives

There are three general types of variable speed drives- DC Motor drives, Eddy Current Drives, and AC Motor drives.Each type of variable speed drive can be divided into different variations. Every variable speed drive system will include an electric motor and a speed control unit. Variable speed drive technology today mainly consists of solid state electronic components in a single system. Older variable speed drive systems used mechanical parts that over time, resulted in failure due to moving and worn parts.

DC Motor Drives

DC drives are also known as DC Motor Speed Control Systems.The speed of a DC motor is directly proportional to armature voltage and inversely proportional to motor flux; either armature voltage or field current can be used to control the motor speed. DC Motors have become expensive and today most dc motor speed control systems have been retrofitted with an AC motor and AC variable speed drive. AC variable speed drives are less expensive than DC systems, are more available and are more efficient than DC systems.

Eddy Current Motor Drives

An eddy currentdrive consists of a fixed speed motor and an eddy current clutch. The clutch contains a fixed speed rotor and an adjustable speed rotor separated by a small air gap. A direct current in a field coil produces a magnetic field that determines thetorquetransmitted from the input to the output rotor. The controller provides closed loop speed regulation by varying the clutch current, allowing the clutch to transmit enough torque to operate at the desired speed. Speed feedback is provided by an integral AC tachometer.

Eddy current drives are less efficient than other types of drives.Nearly all eddy current motor drive systems are obsolete today. There are few manufacturing facilities across the globe that still use eddy current motor drive systems, and when the equipment fails, it’s expensive to repair and often impossible to replace.

AC Motor Drives

AC variable speed drives are also known as, VSDs, variable frequency drives, VFDs, inverters, adjustable speed drives, and micro drives. AC variable frequency drives are used in many applications such as swimming pool pumps, air compressors, conveyor belts, lathes, mills, food processing production lines, waste water treatment pumps, HVAC fans and blowers, and many more applications in the industrial manufacturing world. Approximately one third of the world’s electrical energy is supplied by electric motors in fixed-speed centrifugal pump, fan, and air compressor applications. This proves thatsignificant energy efficiency improvement opportunities are available in the industrial manufacturing world if older DC motor speed control systems and eddy current drive systems are retrofitted with AC variable frequency drive systems.


Most manufacturers currently seek to replace their eddy current and DC variable speed drive systems with AC variable speed drive systems. Today, technology has reduced AC variable speed drive systems’ cost, physical size, and has improved performance through advances in semiconductor switching devices, simulation, control techniques, and control hardware and software. Manufacturers across the globe capitalize on AC variable speed drive technology to save money on their power bill, increase quality control, decrease production downtime, and improve overall efficiency in production lines.