How a Variable Frequency Drive Works

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Variable Frequency Drives (VFDs) are tools for converting input sources into variable frequencies to control operation at a steady rate. In addition to controlling power frequencies, VFDs are used to control shaft positions using encoders and resolvers. A VFD’s ability to smoothly control variable frequencies makes these devices essential in applications such as pumps, motors, blowers, controllers and conveyor belts.

What’s Inside a Variable Frequency Drive?

Every VFD is unique and can be custom-built for different equipment and machinery. A majority of VFD systems use solid-state electronics controllers to convert input sources. This system consists of an inverter module, a bridge rectifier and a converter that allows the system to operate at smooth variable frequencies.

Types of VFDs and VFD Functions

In the past 50 years, technical advances have resulted in controllers that can handle increased voltage and current ratings in solid-state power devices. Since the introduction of VFDs in 1983, they have become the standard in current switching devices.

Variable Frequency Drives come in three types:

  • Current source inversion: Regenerative-power-capable drives with a clean current used in industrial power applications and signal processing.
  • Voltage source inversion: Poorly powered nongenerative drives that are rarely used because of their difficulty functioning.
  • Pulse-width modulation: Powerful drives capable of yielding perfect sinusoidal drive integrals. Their high efficiency and low cost make them the preferred VFD.

Voltage-Source Inverter Drives

Most VFD systems are voltage-source inverter drives that convert AC line inputs into AC inverter outputs. Instead of being converted as AC/DC, voltage-source inverters use a DC to AC configuration. Voltage-source inverters use Volts per Hertz drive controls in variable-torque applications. VFDs can be used for both open loops and closed loops, both of which are desired over Volts per Hertz VFD drive controls.

Manufacturing VFDs

VFDs in the manufacturing industry are used to reduce amperage spikes upon motor startups in rotating equipment. Like a soft starter, VFDs prevent inrush and reduce wear on motors, though they do not provide the same surge protection as a soft starter. VFDs in the manufacturing sector work by stopping and starting AC electric motors and allowing them to operate only when needed. This control reduces power costs by up to 50% or more.

Power-Saving VFDs

In today’s market, 60 Hertz is the most common frequency for direct currents. Variable frequency drives help electronic circuits save power by converting their line power into a pulsed output voltage that works at varying alternating frequencies. When paired with the correct electric motor, VFDs significantly lower operating costs by reducing AC variable frequency drives.

Uses for VFDs

Variable frequency drives frequently see use in motors for:

  • Compressors
  • Conveyers
  • Extractors
  • Extruders
  • Fans
  • HVAC systems
  • Pumps

Find the Right VFD at Global Electronic Services

Global Electronic Services has a wide selection of VFDs from trusted manufacturers, including Autocon, Delta, Lovejoy, Met and Robicon, and a turnaround time of only one to five days so the VFD your business needs gets there as fast as possible. Every product we sell comes with an 18-month warranty, and our in-house repair services are here if your components ever need attention. Contact us online or at 877-249-1701 and request a free quote today.

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