Users should be cautious in their search for VFDs and purchase fully tested UL VFDs certified on single-phase inputs with three-phase outputs. Click here to download the pdf. SPX FLOW appoints Dynapumps as new channel partner in Australia; Honeywell ControlEdge PLC wins 2019 exida cyber award; Valcor Engineering goes greener; Future Neles signs valve distribution agreement with Axel Larsson Maskinaffär AB. 5: A VFD’s input current should be higher than its output current. I can only assume it may have something to do with the harmonic content of the conductors feeding the VFD as apposed to the conductors leaving the VFD once the line reactor has filtered out the harmonics to the pump. Let us start with FLAs. In some pumping applications, the pump manufacturer may size the motor to operate into its service factor to get the pump to maintain flow or head conditions as required. You accept the use of cookies or other identifiers by closing or dismissing this notice, by scrolling this page, by clicking a link or button or by continuing to browse otherwise. National Electrical Manufacturers Association, Control, flow management and monitoring of compressors, Dresser Natural Gas Solutions launches multipoint injection for Texsteam pumps, Product Focus: Mixers, Transmitters, and Pumps, Case Study: Chemical metering pump adds precision dosing, Pulsation of flow and pressure in piping of reciprocating pumps and compressors. Volts/Hertz ratio. The issue is that the VFD is unable to cool itself as it generates heat while producing current to run the motor. The best way to get reasonable motor current values for motors running from VFDs is to read it from the VFD itself, which inherently includes the necessary hardware and software to calculate motor current. When under load the input current increases to about 200A, while the output current shoots up well over 300A. Equipment alignment will always be better if the correct nameplate motor current is determined and the VFD is sized based on those facts. Oh for crying out loud...how long have I had a computer(30 years)...how long have I "known" this?! A typical VFD has six diodes to direct the flow of electric current. Learn more about us. When only single-phase power is available, some VFDs can use single-phase input power to provide three-phase output power and operate a three-phase motor. Troubleshooting at the input starts with testing power and supply. This means the motor uses 13.4 FLA at 230 V AC while only using 6.7 full load amps at 460 V AC. The higher the ambient air temperature, the hotter it is when running the VFD. At 1400rpm (full running speed), and no load, my output current is about 80 amps and measured output voltage is about 370V while my input current is approximately 35 amps. VFDs need a certain amount of heat to keep all components operating at their optimal designs. Confusion often surrounds the proper sizing of variable frequency drives (VFDs), and sometimes, knowing when and how to choose one may be difficult. I calculate that as follows: 16.0 A (Max 1-Phase Current) * [ 5.6 A (Max Motor 3-Phase Current) / 9.3 A (Max VFD Output)] = 9.63 A These overload motor amps are used to size the VFD. This overload condition may be required to provide the necessary torque to overcome the starting inertia or during heavy operating conditions in some loads like rock crushers, positive displacement pumps, belt presses, cranes or other applications. Let’s begin with the basics by learning how to read a motor nameplate. Most pumping and fan VFDs today are sized with variable torque as their primary sizing. Approximately how much energy is saved by operating a pump motor at 85% speed as compared to operating the pump motor at full speed to provide the same liquid flow rate? Sign up for Flow Control Network eNewsletters. 1 ph in 3 ph out. Sean Fitzpatrick is global key account manager for Danfoss Drives. Some manufacturers provide specific VFD units designed for this while others simply oversize the VFD and derate for this feature. He may be reached at jbergman@danfoss.com. All rights reserved. The right design will put the right pump with the right system. To learn more, please refer to the cookie policy. FLAs are the amps on which the motor will draw when operating at full load and full speed. When measuring VFD input current and output current some people become mystified with the current values read on the input side vs the output side. If you are referring to the vfd nameplate stating a higher input amp number than output amp number, it has been explained above. For a better experience, please enable JavaScript in your browser before proceeding. In case of sale of your personal information, you may opt out by sending us an email via our Contact Us page. NE (9.06 miles @5.9 Degrees from Winged Horses). A motor’s nameplate shows how many full load amps at how many volts the motor uses. A chemical processing plant partners with pump solutions provider to solve reliability issues and help meet increased production needs. When operating in this condition, it is important to verify the continuous amps required to operate the motor in its new normal conditions. The higher the altitude, the less heat the VFD can exhaust, requiring a derating or reduction in its ability to produce output current. At frequencies below 60Hz, the output voltage from the VFD is below the line voltage. What about low-rpm motors? You must log in or register to reply here. Sometimes the motor nameplate details the service factor amps of the motor, otherwise it is critical to multiply the running amps by the service factor to ensure proper VFD sizing. A VFD’s maximum current is a function of its design, and you’d have to get that from the drive manufacturer. But the VFD INPUT was about 0.8 amps, which is obviously wrong. VFDs convert input AC power to DC and then invert it back into a modified three-phase AC output. This website or its third-party tools process personal data (e.g. I would like to know why the input current of a VFD would be differnt than the output from the VFD to say a 200hp, 3ph, 480v motor load. A utility standardized and defined best practices for its applications, improving operations while saving time and money. At 1400rpm (full running speed), and no load, my output current is about 80 amps and measured output voltage is about 370V while my input current is approximately 35 amps. While it may sound simple, it is how this happens that can be quite complicated and is out of the scope of this article. VFDs supply current that, with the correct voltage and frequency, makes the motor run at the desired speed. Or am I way out in left-field on this one. The nameplate in Figure 1 shows that motor current is based on the input voltage: volts (V) 230/460, full load amps (FLA) 13.4/6.7. New products from Endress+Hauser, Blue-White Industries, Xylem, and Flow Technology. Input current of 19.6 and output of 9.6. press the "insert" key on your keyboard probably located near upper right corner. Myth No. Register for the world’s largest manufacturing technology forum for free today to stay in the know. Practical Machinist is the easiest way to learn new techniques, get answers quickly and discuss common challenges with your peers. Flow, cavitation, piping and nozzle loads at suction of pumps. It was about 3.9 amps for an unloaded 3 hp motor. In order to measure the voltage, a low-pass filter is required to remove the high-frequency component. New products from AutomationDirect, Wilden, Armstrong Fluid Technology, and ABB. As the air thins with higher altitude, the ability of the air to transfer heat out of the VFD is reduced. Practical methods in rotating equipment vibration analysis. I have a 250HP VFD supplied with 472VAC. Waveform of a 240/120-Volt single-phase system. Again, it is critical when sizing the VFD to know as much about the operating conditions as possible. Now throw in the VFD that is only input with single phase and has three phase output - the input and output currents are never the same or even close to the same. What is normal or standard overload? VFDs are commonly referred to as adjustable speed drives, adjustable frequency drives, AC drives, microdrives and inverters. Variable frequency drives (VFDs) are mechanical drive systems used to control alternating current (AC) motor speed and torque by varying motor input frequency and voltage. Powered by vBulletin® Version 4.2.5 The sizing may require the need to derate for higher ambient temperature or cool the VFD with cooler air. The derate value varies by manufacturer and by size, so no good rule applies other than to visit the manufacturer’s website or call the tech support hotline. With a high ambient temperature, the VFD is unable to dissipate the generated heat it needs to dissipate and keep itself cool.

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