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Variabl frequency drives (VFDs, variable speed drives, VSDs) are an excellent choice for adjustable-speed drive users. They allow drive users to fine-tune processes while reducing costs for energy and equipment maintenance.

At water and waste-water facilities, the applications of variable frequency drives (VFDs) are so popular.

Figure below illustrates the reduced energy consumption of Variabl frequency drives (VFDs, variable speed drives, VSDs) over valve control systems at water and waste-water facilities.

For applications where flow requirements vary, mechanical devices such as flow-restricting valves or moveable air vanes are often used to control flow, which is akin to riving a car at full throttle while using the brake to control speed.

Further, the rapid rise time of the pulses may cause trouble with the motor bearings. The stray capacitance of the windings provide paths for high frequency currents that close through the bearings. If the voltage between the shaft and the shield of the motor exceeds few volts the stored charge is discharged as a small spark. Repeated sparking causes erosion in the bearing surface that can be seen as fluting pattern. In order to prevent sparking the motor cable should provide a low impedance return path from the motor frame back to the inverter. Thus it is essential to use a cable designed to be used with variable frequency drives (VFDs, variable speed drives, VSDs).

In big motors, a slip ring with brush can be used to provide a bypass path for the bearing currents. Alternatively isolated bearings can be used.

The output voltage of a Pulse Width Modulation (PWM) variable frequency drive (VFD) consists of a train of pulses switched at the carrier frequency. Because of the rapid rise time of these pulses, transmission line effects of the cable between frequency inverter (vfd) and the motor must be considered. Since the transmission-line impedance of the cable and motor are different, pulses tend to reflect back from the motor terminals into the cable. The resulting voltages can produce up to twice the rated line voltage for lone cable runs, putting high stress on the cable and motor winding and eventual insulation failure.

Increasing the cable or motor size/type for long runs and 480v or 600v motors will help offset the stresses imposed upon the equipment due to the VFD (modern 230v single phase motors not effected). At 460 V, the maximum recommended cable distances between VFDs and motors can vary by a factor of 2.5:1. The longer cables distances are allowed at the lower Carrier Switching FrequencY (CSF) of 2.5 kHz. The lower Carrier Switching FrequencY (CSF) can produce audible noise at the motors.

A thorough understanding on how to match frequency inverter to the driven load is the key to a successful application. When applied properly, frequency inverter (variable speed drive) is the most effective motor controller in the industry. Variable frequency drives (VFDs, variable speed drives, VSDs) are affordable and reliable, and having flexibility of control, plus offering significant electrical savings through reducing electric bills.

Today Frequency Inverters are widely used in a variety of applications for various reasons.

In pump and fan application, variable frequency drives (VFDs, variable speed drives, VSDs) are the most effective energy savers. In most facilities, centrifugal pumps and fans run at one constant speed. Traditionally an automatic value, or some mechanical means varies fluid flow rates. With a frequency inverter (variable speed drive), you can change motor speeds electronically. By being able to adjust a pump or fan speed to get the desired rate, you can significant reduce energy cost. Thus money is saved through reducing electric bills.

Cost-effective variable frequency drives (frequency inverters) from GreenDriv Tech Limited:

Variable frequency drive (VFD, adjustable frequency drive) has been successfully applied to large boiler feedwater pumps in power plants, hot water circulation pumps in commercial buildings, and for waste water treatment plants in our city. Variable frequency drives (VFDs, adjustable frequency drives) provide soft-start capabilities, which will decrease electrical stresses and line voltage sags associated with full voltage motor start-ups, especially when driving high-inertia loads.

Variable frequency drive (VFD) controllers, which are designed to operate at 111 V to 690 V,  are often classified as low voltage drives.

Low voltage variable frequency drives (VFDs) are typically designed for use with motors rated to deliver 0.2 kW or 1/4 horsepower (hp) up to several megawatts. For example, the largest ABB ACS800 single drives are rated for 5.6 MW.
World class low voltage variable speed drives from GreenDriv Tech Limited:
 

Medium voltage (MV) variable frequency drives (VFDs) are generally rated amongst the following voltages : 2,3 KV - 3 Kv - 3,3 Kv - 4 Kv - 6 Kv -6,6 Kv - 10 Kv - 11 Kv

One common application of this device: converting bulk amounts of power from one distribution standard to another.

One other typical application is: Frequency inverters are often used to control the speed and the torque of AC motors too. The most typical frequency inverters topology is the  3 phase two-level voltage source inverter. The phase voltages are controlled using the power semiconductor switches and pulse width modulation (PWM). Semiconductor switching devices and anti-parallel connected freewheeling diodes form a bridge, which can connect each motor phase to the positive or negative dc-link potential. The pulse width modulation (PWM) changes the connections of the phases between the positive and the negative dc-link potentials. Thus the fundamental wave voltage has the desired frequency and amplitude. The motor reacts primarily to the fundamental voltage and filters out the effects of the harmonic voltages.

World-class cost-effective frequency inverters from GreenDriv Tech Limited:

Another application of frequency inverters (frequency changers, frequency converters) is in the aerospace and airline industries.

Frequency inverter, in different countries, exists different names, including frequency changer, frequency converter, variable speed drive, variable frequency drive, adjustable speed drive, adjustable frequency drive, ac drive, variable voltage variable frequency drive, vvvf drive, even microdrive.

A frequency inverter is an electronic device, that converts alternating current (AC) of one frequency to alternating current (AC) of another frequency. Frequency inverter may also change the voltage, but if it does, that is incidental to the principal purpose.
The image of frequency inverter from GreenDriv Tech Limited

An electric car is eco-friendly, sometimes with zero emissions, is an automobile that uses an electric motor for propulsion. It's a variety of electric vehicle (EV). Convetional gas-powered cars use common propulsion methods, such as the internal combustion engine (ICE).

Image of plugged-in electric car:

As mentioned above, electric cars are usually powered by on-board battery packs, and as such are usually battery electric vehicles (BEVs). Electric cars are the practical forms of transportation, which can be inexpensively recharged overnight.

As one new form of eco-friendly transportation, hybrid-electric vehicles (HEVs) combine the benefits of gasoline engines and electric motors. Current hybrid electric vehicles (HEVs) integrate an internal combustion engine (ICE) and an electric motor and battery. Improved fuel economy, increased power, or additional auxiliary power for electronic devices and power tools, are the benefits of hybrid-electric vehicles (HEVs). There are a lot of hybrid electric vehicles on the market, and most automobile manufacturers have announced plans to produce their own HEVs, or have manufactured some models, such as Toyota, Honda, Ford.

How do hybrid electric vehicles (HEVs) work?
 

The basic types of hybrids include 3 types: mild hybrids, full hybrids, plug-in hybrids. These 3 hybrids funtion differently.

The hybrid-electric vehicle (HEV) produces less emissions from the conventional internal combustion engine (ICE) than a comparably-sized gas-powered car, as the hybrid electric vehicle (HEV)'s gasoline-powered engine is usually smaller than a pure fossil-fuel vehicle, and if not used to directly drive the vehicle, can be geared to run at maximum efficiency, further improving fuel economy.
 

Let's check the types by degree of hybridization.

1. Full hybrid. Also called a strong hybrid sometimes. Full hybrid electric vehicle is a vehicle that can run on just the engine, just the batteries, or a combination of both. The examples of full hybrids include Ford Escape Hybrid, Ford Fusion Hybrid, and popular Toyota Prius.