Electric motors are essential to millions of companies across various industries, including transportation, manufacturing, agriculture, and construction. For the business owner, purchasing electric motors typically represents a substantial investment in improved productivity and longevity for the business. However, the electricity needed to power that motor represents a month-over-month operational expense.
Regardless of their size, electric motors consume a significant amount of energy to power everything from small tools and appliances to elevators and overhead cranes. The use of electric motors is so widespread that over 40% of the global electricity consumed annually is used to power them. To help reduce these energy costs, manufacturers have developed various controllers to adjust the motor’s speed during operation.
Deciphering the Acronyms
When discussing motor controls, the two most popular options are the Variable Speed Drive (VSD) and the Variable Frequency Drive (VFD). Most people assume that the terms can be used interchangeably because they can both be used to adjust the speed of an electric motor. However, each option uses different technologies to accomplish this goal, which creates confusion.
A VSD refers to any controller that can change the electric motor’s speed, while a VFD refers to those controllers that change the voltage or frequency to increase/decrease the motor’s speed. In short, all VFDs are VSDs, but not all VSDs are VFDs. Much like all Harleys are motorcycles, not all motorcycles are Harleys.
Now, let’s examine those electric motor control differences in greater detail.
Variable Speed Drives (VSD) for Electric Motors
VSD is a broader term encompassing different options to control a motor’s speed through voltage, current, and torque adjustments. Unlike their counterparts, VSDs can be used with AC and DC motors with equal success. VSDs offer greater flexibility in motor control options, making them suitable for a broader range of applications.
Common examples of VSDs include.
- Variable Voltage Drives (VVDs)
- Variable Torque Drives (VTDs)
- Material Handling Equipment
- Pumping Systems
- HVAC Systems
- Manufacturing Equipment
Variable Frequency Drives (VFD) for Electric Motors
VFDs control the speed of AC motors by adjusting the frequency and voltage of the electricity supplied. The incoming AC power is converted into DC power, then inverted back to AC power at a variable frequency. Primarily designed for AC motors, VFDs reduce energy consumption while offering precise speed control and improved operating efficiency, making them particularly useful for applications that require variable speeds and torque control.
Common options include.
- Volts/Hertz Control
- Sensorless and Flux Vector Control
- Pulse Width Modulation (PWM)
- Current Source Inverter (CSI) Drives
- Voltage Source Inverter (VSI) Drives
As you can see, both VSDs and VFDs adjust the amount of power sent to the motor to control speed; however, choosing the best option depends on your specific electric motor and application. If you have any questions about VSDs or VFDs, the Hi-Speed Team is ready to help. You can reach the electric motor drive experts at 1-800-713-0103 or send us an email.
The Benefits of VSDs and VFDs
There are several reasons why you should consider investing in variable speed drives (VSDs) for your electric motors and attached equipment.
Improved operational efficiency
The need for manual labor can be dramatically reduced, as the system controlled by these drive options can be automated to save valuable man-hours and associated labor costs.
Reduced energy consumption
Variable speed drives allow the motor to run at partial load, instead of full load, to reduce monthly utility bills by up to 50%.
Capital expenditure savings
The immediate reduction in electrical consumption ensures a significant ROI for the VSD investment costs. Depending on the application, the VSD could pay for itself within just a few months after the installation is complete.
Maintenance and spare part cost savings
With these drive options, the stress on the mechanical equipment during startup and operation can be significantly reduced. As a result, the electric motor bearings, shafts, and rotors last longer, which reduces repair and maintenance costs for the facility.
When selecting a motor controller, it is essential to consider the specific requirements of the application and choose a controller that best meets those needs. Most electric motor manufacturers offer a comprehensive range of VSD and VFD options for their motors, which can be viewed on the company websites listed below.
TECO-Westinghouse
As part of our commitment to keeping you up and running, the Hi-Speed Team is standing by to answer any questions you may have regarding electric motors and selecting the best VSD systems for your business. You can submit your questions via email or call us directly at 1800-713-0103.
Related Articles and Information
Due to your interest in selecting the right VSD for your electric motor, we’ve compiled some additional articles that may be helpful.
What Does Noise Tell You About Your Electric Motor?
The Essential Guide to Getting Your Electric Motors Serviced and Repaired
Best Electric Motor Repair Practices