Variable Frequency Drives (VFD) that do not have either an AC line reactor or a DC bus choke, will typically exhibit a THDi greater than 85% at all loading conditions. The THDi is dependent on the conduction angles of the rectifier. Any inductive reactance in the supply, plus the overall impedance will reduce the peak charging current to the capacitors and increase the conduction angle and reduce the THDi.
So VFDs with standard 6 pulse rectifiers will produce harmonic currents in the supply ranging from around 38% to 100% depending on the load and the reactance in the circuit. VFD with active front end can have a reduced harmonic current down to around 5% provided that the active front end is optimised for harmonics rather than regeneration. These harmonic currents are drawn from the supply the whole time the variable frequency drive is operating.
So VFDs with standard 6 pulse rectifiers will produce harmonic currents in the supply ranging from around 38% to 100% depending on the load and the reactance in the circuit. VFD with active front end can have a reduced harmonic current down to around 5% provided that the active front end is optimised for harmonics rather than regeneration. These harmonic currents are drawn from the supply the whole time the variable frequency drive is operating.
Advances in high-speed electric motor technology along with improvements in the cost and the performance of VFD (variable frequency drive) systems make direct coupling of a gearless electrical motor to a pump worth considering for many services requiring large VFDs. Brushless synchronous motors with two-pole rotors often suit high performance duties. Special applications may benefit from other options such as induction electric motors.
AC drives are designed to provide variable speed control. They maintain the optimal speed required for an application to enhance production and save energy. Low- and medium-voltage drives gradually accelerate and decelerate motors and pumps, helping protect mechanical components and extend their life, while reducing inrush currents, which helps save energy. AC drives are used in a broad range of industries and applications—including HVAC, water and wastewater, and oil and gas.
Due to power electronics technology and microelectronics technology rapid development, variable frequency drive reforms and upgrades speed also is faster, introduce new products, improve performance continuously, enrich and strengthen function constantly. China domestic market has lots of variable frequency drive brands, such as Danfoss, ABB, Gozuk, SIEMENS, GE, Schneider, etc.
Since the 21st century, China variable frequency drive industry is highly fission. Many foreign brands begin to set up factories in China, the implementation of the localization of business. See Appendix major foreign brands in the Chinese mainland investment. On the other hand, the original domestic brands personnel and funds continue separation, the establishment of a number of enterprises, mainly concentrated in coastal areas such as Guangdong, Zhejiang, Shandong, Shanghai and other regions.
My personal preference is for an AC line reactor simply because it does a better job of protecting the variable frequency drive from the line and the line from the drive. I've always viewed a DC bus reactor on a PWM drive as a cheap attempt at filtering to save space and money over the better protection afforded by a line reactor.
AC Drives has to be selected by current and not power. That should be same but is not always. Immerged pumps for examples are using more current than standard ac motor for same mechanical power. In general current is more less linked to torque. Be aware than bellow 50% of nominal torque/current the AC drives selection can be different.
As nowadays there is a trend in green energy production and energy efficiency, what solutions/applications would you recommend in reduction consumed energy of a motor driven by variable frequency drive.
The engineers in AC Drive China are very professional in Chinese automation industrial control fields, provide you comprehensive energy saving solutions.
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Frequency directly represents no of rotation of rotor for that machine,
the higher the frequency the more the rotation of the rotor, i.e. the
rpm of the motor there by result ...
Due to power electronics technology and microelectronics technology rapid development, variable frequency drive reforms and upgrades speed also is faster, introduce new products, ...
Since the 21st century, China variable frequency drive industry is highly fission. Many foreign brands begin to set up factories in China, the implementation of the localization ...
My personal preference is for an AC line reactor simply because it does a better job of protecting the variable frequency drive from the line and the line from the drive. I've ...
As nowadays there is a trend in green energy production and energy efficiency, what solutions/applications would you recommend in reduction consumed energy of a motor driven by ...
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