Another important thing to consider when purchasing a VFD. Purchase quality line reactor & if critical loads go with the bypass feature that has three contactors. M1 powers drive in put M2 is on output side & M3 when closed urs interlocked so M1 & M2 contactors remain open. Had some bypass VFD'S have a test position on hand, off, auto selector switch that I never done it but you can troubleshoot drive while motor is running full speed thru the M3 bypass contactor and believe it allows M1 input contactors to supply power to drive.
This for me was a timely piece....'sizing'... I've looking for reasons for a overheating issue with the ( a supposedly 150% 'appropriatley' rated chineese generic) VFD . My project is a current Commercial Front loader Washer but with 'cooked' control electronics: but everything else in good seviceable order for the decade or more. Mind you; 'she's no longer what could be strictly described as automatic. Happy now to put down a few hundred bucks on a nameplated VFD unit.. Big thumbs up.
We had over 500 VFD'S from where I retired from 2 to 1,750 HP. The extremely knowledgeable salesman that I ordered replacement or a drive for a new location he always told me that drives are rating in power ( KW ) & not horsepower. Of course every VFD he sold us had a horsepower rating along with ampere. Would send him a picture of the think it was a combination of 26 letters & #'s from serial # on old drive and he cross referenced that also. On a few critical pieces of equipment we ordered the next size HP. For a 40 HP motor would order a 50 HP drive and a 60 HP motor would order a 75 HP drive. Would downsize input fuses and adjust trip Amps on overload block.
Thanks for watching my videos and adding your two cents Garbo! Drives are sized by the heat load the power electronics can bear/dissipate, this heat is directly proportional to current and thus drives are sized according to amps out. In North America we use HP to denote mechanical power and KW to denote electrical power.
Great video. However I have one observation about the statement that VFD Horse Power( say Power Rating) shall match with motor Horse Power. In my understanding motor rating means shaft power out put which will require bigger electrical input depening upon the efficiency of motor. Further there will be electrical power loss( I2R loss) in the connecting cable between VFD and the motor terminal, whatever small percentage it may be. So in my opinion, VFD output shall not only be able to meet shaft power, but also total power loss in motor plus cable loss. Kindly correct me if you feel otherwise.
Hi Sanjay, great point. You are correct in theory, but lucky for us, all VFD manufacturers have taken the guesswork out of this decision and rated their drives large enough to compensate for this.
Cranes and hoists are a fairly prototypical constant torque load, so any drive with a constant torque rating should be good. Most cranes/hoists have a control system consisting of a forward run reverse run and up and down limit switches so any drive with digital inputs should be fine. Lastly some crane/hoist application wills require braking resistors in order to control the lowering of the load so a built in brake transistor can be helpful. As such the A510 is a good drive for these as it has all of the above requirements: www.emotorsdirect.ca/search?keywords=a510
Say you double the rpm of the motor by doubling the frequency, does that also double the motor's power output? Would you need a VFD with twice the power rating?
Hi Robert, most motors are not rated for overspeed conditions. The motors that are will explicitly state this in their data-packs. Motors rated for overspeed will go into a constant power state when frequency is raised past rated frequency where torque drops off in direct proportion to speed. For example 1.5x speed = 2/3 torque, 2x speed = 1/2 torque. - Keith
I have a 3 kW Cavity pump in my factory that is driven by a VFD Drive. The datas of my VFD are (3 kW CT, 4 kW VT). Now, I want to change the 3 kW pump with one that is 4 kW, should I change the drive also? As a Note, my pump should carry the pressure of oil almost constant.
Hi Rilind, It depends on if your pump is considered a Variable Torque or a Constant torque load, you would then need the appropriately rated VFD to go along with it. You may want to contact the manufacturer of the pump to find out more information.
"Most modern motors are rated for VFD" - does that mean that retrofitting an old lathe motor using belts to a VFD is bad Idea and I should consider changing out the motor for a VFD rated one as well?
I've got a bandsaw with a CMG 3Phase 380-420v 3.3kw 4.5A 1430rpm motor on it. Can you recommend a drive to run it on single phase 230v please? Could you mention the potential current draw on the single phase supply also? Many thanks! Great video!!
Thanks for the question. Can you make do with less than 1/3 of the rated torque? I ask because 380 to 420V at 1500 RPM would suggest that this motor is rated at 400V at 50hz. The equivalent 60hz voltage would be 480V. At 60hz the maximum overvolt on most drives is about 10% with some going as high as 20%. So there is no way to get anywhere near 480V. Torque goes down by the square of voltage so with the overvolt 260/480 is about half so you'll experience a torque loss of just over 70%. You'd need a transformer to get the voltage up to 480 and then a VFD can convert to 3 phase. Hope this makes sense - let me know if I can clarify any of this.
Hi, thanks for the useful information. I'm having a speed issue on a 3 phase asynchronous motor with specs as 4kw/1435 rpm/ 380v. Upon startup it rises to 15+ bar pressure which is too high for a petrol line. Would a VFD (5.5kw) solve the issue of controlling the speed on it?
Thank you for the question Hamid. Generally speaking, pressure should be proportional to RPM. A VFD or a soft start should be able to mitigate this problem. An exception may be if you're working with a fixed displacement pump.
Thank you very much for the prompt reply. I have been able to resolve the problem using the VFD mentioned above with a soft start. And yes, it is a fixed displacement pump. With a pressure switch attached for automatic cut off at 3 bar max, and it's working perfectly fine.
Are most VFD's capable of converting single phase to three phase? It looks like you just use L1 and L3 as the input, then oversize the VFD, is that correct?
Great question. I just did a video on this topic. Check it out here for my notes on how to use a VFD to convert a single phase to three phase ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-skEaxx5YJbI.htmlsi=_5QgNz3fmsxQYiGZ
Whether you oversize the VFD depends on the motor horsepower. In under 3 horsepower, you can usually find a single phase VFD (ex. 3 HP three phase motor, 3 HP single phase VFD). Single phase VFDs are harder to find in larger sizes so typically, you'll source a three phase VFD and double the size (ex. 10 HP three phase motor, 20 HP three phase VFD).
Hi - thanks for the question. There are two options when choosing a drive for a phase conversion application. 1) Choosing a drive rated for single phase application 2) Derating a drive a rated for three phase application Almost all the VFDs we sell have 6 input diodes, two for each single phase of the input and so the three sets of diodes share the heat/current load evenly. In a single phase input, all the heat and current goes through one set of diodes causing heat and current to concentrate. Single phase rated drives oversize the output transistors to match the heat load so something like the Sinus M 0014 2S/T would work without derating/oversizing. The rule of thumb for derating is to divide the rated current capacity by half. So a 10HP drive becomes a 5 Hp drive thus if we were looking in the A510 series of drives we would have to go with the A510-2020-C3-U or larger.
Hi Sir, can i use vfd to a press drill machine with the name plate of 3 phase induction motor, 4pole, 1.5hp, 60hz, 440volts, 2.75ampere, 1700rpm, ins F, amb 40degC, cont.rating. Thanks in advance, Paul Mercado
Thanks very helpful. I'm using a 55 year old 3ph 2 speed 1.5hp Swiss made EMB motor and it works very well but I only have a single phase supply. So I connected up a 2kW VFD and it is working okay apart from not enough low speed torque. Is there a way to correct for this?
Hi Jeff, thanks for the question. A motor that old isn’t designed to be used on a VFD and will probably overheat by slowing it down as little as 30%. You would need to buy a new motor rated for the turndown that you’re needing.
If you're located in Canada or the USA, you'd be looking for a 20HP VFD (this is approximately a 17HP motor converted from kW). Your vendor would want to know your voltage you're running and the voltage of the motor. Also, what environment the motor is running in, so that they can advise the appropriate enclosure/features. I'd also confirm if this motor is VFD rated. From what I can find online, Siemens stopped producing this motor in 2018 and the information online is limited. Lastly, consider using an AEGIS Grounding Ring to limit shaft currents and prolong the life of your motor. Contact our team for future assistance if you're located in Canada or the USA: www.emotorsdirect.ca/contact-us
I would like to add a big red STOP mag-switch with a VFD I'm installing on a old rockwell delta bandsaw (1.5hp). I could put the switch between the source and VFD or VFD and motor. Any recommendation for placement? Thanks, Dennis
I'd recommend putting a stop switch on the VFDs emergency stop contacts and that should safely disconnect the power. If you absolutely must put the switch directly on the line/load side the line side is preferred but it is it important to use a switch that won't chatter/arc.
Best practice is to have the VFD as close to the motor as reasonably possible as longer cables mean more power loss as well as increased interference. You can always mount a remote keypad or remote controls away from the VFD at a much lower cost and with fewer consequences than moving the VFD away from the motor. Hope this helps!
Hello , I would like to know what size should the vfd be if I have an urban lift motor rpm 1385, cv.:5.5 , volt: 220/380 , Amp: 23/13.3 as shown on the motor plate. also what is the recommended electrical installation that should be used as protection for both the vfd and the motor? thanks
Hi Ahmad, thanks for the question. This depends on the local electrical code and the specific application. Depending on the sensitivity of the motor, dv/dt filters or load filters may be used. For the line side, there are many different types of filters and mitigation equipment that can be used in addition to fuses, contactors, isolators and sometimes even bypass systems. There is no single answer to this question but rather a number of possibilities that need to be weighed according to the sensitivities of the application.
I have an older 25 hp 3 phase compressor with a F insulation . I’d post a pic of the motor tag if I could . Can you please tell me what vfd would work for my application ? Thank you for your time .
@@carlscarborough6382 Hi Carl, thanks for the question. We typically work with WEG, TECO Westinghouse, KB Electronics, and Leeson VFDs. Here are some options, but would need to confirm your voltage and use case for the VFD to make a specific recommendation: www.emotorsdirect.ca/controls/vfd?hp-combined=25&input-phase=3
