VFD Drives For Dummies: VFD is an abbreviation that stands for “variable frequency drives”. VFD Drives are also called “variable speed drives”, “adjustable speed drives”, “electric motor speed controllers”, and “inverters”. VFD Drives For Dummies: Every VFD hasits own component characteristics, so how each VFD works is dependent upon components within the VFD. Most VFD Drives for Dummies integrate a solid state electronics controller consisting of a bridge rectifier, a converter, and an inverter module.
Voltage-source inverter drives are the most common VFD Drives For Dummies. These drives convert AC line input to AC inverter output. There are some applications that use common DC bus and solar applications. These type of drives are configured as DC to AC drives. The bridge rectifier converter for volts per hertz drives is configured for 3 phase AC electric motors. The majority of variable frequency drives contain electronic circuitry that converts 60 Hertz Line power into direct current. The variable frequency drive converts this line power into a pulsed output voltage that duplicates varying alternating current to a desired frequency (speed). VFD drives were first introduced in 1983, and the insulated gate bipolar transistor has in the past 20 years become the standard for VFD drives as an inverter switching device.
VFD drives for dummies: Manufacturers will apply variable frequency drives to rotating equipment to reduce amperage spikes upon start up of large electric motors. Choosing the right VFD for an application will benefit rotating equipment by providing less wear on the electric motors where applied. Adjusting the acceleration and deceleration time of electric motors can extend the lifespan of an electric motor. Variable frequency drives provide the ability to control the frequency of starting and stopping of an AC electric motor. This ability allows an AC electric motor to only operate when needed for the equipment its rotating, and electric motors have a longer lifespan if they are only running when they need to be.
Approximately one third of the worlds electrical energy is supplied by electric motors in fixed-speed centrifugal pump, fan, and air compressor applications. These fixed-speed applications hardly ever require the full load speed (RPM) of the electric motor in which theyre operating. By installing a VFD to these applications, electric motor speeds are reduced, and power costs can be reduced by 50% or more. Technology has allowed cost and physical size reduction of variable frequency drives, and has improved performance through advances in technology.
Properlypaired VFD drives with the correct electric motor will significantly reduce operating costs for manufacturers. This is particularly true for variable torque loads such as fans, blowers, and pumps. Blowers are often used with dampers to control air flow; these dampers may operate either manually or automatically. When dampers are closed, 50% of the electric motor current will drop to approximately 60% of full load nameplate current. By utilizing variable frequency drives in blower applications, the current draw of the motor will be reduced 30% for every 10% drop in speed. The same electric motor operating from an AC variable frequency drive at 50% speed, will draw approximately 20% of the full load current.