Vfd 5p3x26

VFD - Variable frequency drive

A modern VFD is a compact, well-developed unit which is relatively easy to install. The cost of a VFD has decreased over the years while the performance has improved. VFDs are usually installed to allow for better process control. The use of VFD is unfortunately not so straight forward. There are numerous technical aspects to take into when deg a VFD controlled pumping system. See technical aspects. A modern VFD is a compact, well-developed unit which is relatively easy to install. Unlike an old VFD, a modern version generally does not require as much power margin compared to ans old one since it uses higher switching frequencies that does not affect the induction motor to the same extent. The high switching frequency however, induces electrical transients which can lead to other problems such as nuisance tripping of control equipment. These transients are also more aggressive against stator insulation. Regardless of the type of pump or VFD used, there are several technical aspects to consider: Clogging: VFD-controlled pumps often run at reduced speeds, which mean that the energy available for the impeller to keep itself from clogging also is reduced. Therefore it is recommended to control the pumps in a way that long periods of running the pumps at low frequencies are avoided, especially in tough sewage applications.

Sedimentation in pipes: Avoid running at low frequencies that will result in velocities in the pipes lower than 0.7 metres per second to minimize the risk of having sedimentation. Nuisance tripping: The high-frequency emission from a VFD can interfere with sensor control systems and other equipment. The use of shielded cables and appropriate filters are therefore recommended. NPSH/power limit problems: The VFD does not dirctly have an impact on the NPSHrequired of a pump. However, decreasing speed with a VFD will in many cases significantly change the duty point for the pump. The new duty point could be at a position on the pumps perfromance curve where the NPSHrequired is much higher than at the duty point at full speed. VFD is used in many sewage pumping applications with the intention of saving energy. Not every pump application will benefit from VFD control. The only way to determine if VFD is the correct choice is to do a thorough analysis. The system characteristics determine if VFD control is economically motivated or not. See economical aspects. Not every pump application will benefit from VFD control. The only way to determine if a VFD will result in an economically satisfying solution is to do a thorough analysis. Pumping with variable frequency drive (VFD) controlled systems can be separated into two different cases: - A variable continuous flow is required by the process (common for industrial applications). The normal way to control the flow is by throttling. The use of a VFD will, in most cases, lead to a substantial energy reduction. - VFD vs. ON-OFF regulation (common for sewage applications). Variable speed drive is used to reduce pipe system losses when pumping. The effect of the VFDcontrol depends on the pipe system used. Systems with high losses relative to the geodetic head will benefit from VFD control, while the impact of a VFD in lift systems (low losses relative to geodetic head), is negligible at best. A though system analysis has to be performed in order to determine whether variable frequency control might be economically motivated. This type of analysis can be performed with Xylem Water Solutions pump selection program,