3 phase VFD with single phase input

[Alan Schaffter]

Alan, that is not our experience. We are running 5hp Leeson motors on Asian sourced VFD's for under $400 a unit. The first installations are getting on for over two years old now with not one single problem reported. This was forced on us by the difference in power supplies between Australia and the US and the need to utilize the VFD to raise the speed back to 3450 rpm and also needing to run the leeson from a 220V single phase power source.

You have a different situation that might justify a VFD, but I suspect it is still more than the price of good used motor as long as your impeller matches. Regardless of the price, still a lot of money for soft start. Two solutions mentioned on the ClearVue website are- mechanical (pulley and v-belt) which would be cheaper, or going with a larger impeller.

[David Kumm]

Alan, your points are valid. Like anything else it depends on the circumstance. I'm running about 2000 cfm over long runs and there is no way to avoid filters. That's a lot of air to send out in the winter or even when humid. You are absolutely correct that the impeller not only needs to be designed to handle higher rpm but also must move more air at higher speed. Most hobby systems run backward inclined or curved blades that operate within a narrow rpm and amp range to avoid burning out motors. They also don't handle high pressure very well so you can't pull lots of air through undersized pipe. I run a straight radial which solves the pressure problems caused by 60' runs but can easily overamp a motor. They need to be monitored but the benefit is more air-7000-9000 fpm through any pipe from 8' to 4". They tend to be loud so I slow it down when just using it to clean the air in the shop. The DC filters are better than the ambient and faster so it serves double duty although not necessarily energy efficient. The impeller itself is a material handling type so it was engineered for a push through system and weighs about 30 lbs. Needless to say the motor shaft and bearings need to handle the speed and weight as well. There are a bunch of things to be careful of- like everything else- but it's worth it to me. And three phase motors are cheap enough used that you can afford the vfd or the RPC and then you have an excuse for old industrial stuff. Dave

[Chris Parks]

You have a different situation that might justify a VFD, but I suspect it is still more than the price of good used motor as long as your impeller matches. Regardless of the price, still a lot of money for soft start. Two solutions mentioned on the ClearVue website are- mechanical (pulley and v-belt) which would be cheaper, or going with a larger impeller.

This may be out of context as I am not sure how to read the above. In our case a change of motor will do nothing in restoring the lost motor speed we experience.

I was originally addressing the cost of a VFD being a thousand dollars where we have found that an adequate solution can be had for way less. I can supply contact details if anyone wants them BTW for direct supply from the Chinese manufacturer. Dealing with these people has been the easiest experience I have had for a long time and no one should feel intimidated by any language difficulty as there are none. They speak and write near perfect English but it is a pity their operating manuals are not written as well. The units we use allow two keyboards to control a single VFD and these can be remotely mounted at the machine(s) using ethernet cables and a splitter. Another advantage of the one we use is profiles can be written to enable different operating situations to be allowed for.

[Alan Schaffter]

Chris, I understand. I took a chance once and ordered a device directly from a PRC company. Item cost and shipping weren't bad- these guys really want to sell their products to the rest of the world. The only thing I would be concerned about is the manual and after sales support.

[Chris Parks]

After sales support from the company I deal with is awesome in capitals. I had some questions so I emailed to them and within five minutes they were on the phone to explain to me what I needed to know. I most probably buy thirty units a year and they treat me like I am their best customer! The manual is definitely a let down as translating technical stuff is always difficult but we get by.

[Stephen Cherry]

http://www.driveswarehouse.com/p-2134-x200-075lfu.aspx

To me, this looks like a well documented, industrial quality drive. They even publish specs on how to run single phase, or with external rectification. Not cheap, but it is an alternative to the non-documented drives (which can be OK also).

[Alan Schaffter]

http://www.driveswarehouse.com/p-2134-x200-075lfu.aspx

To me, this looks like a well documented, industrial quality drive. They even publish specs on how to run single phase, or with external rectification. Not cheap, but it is an alternative to the non-documented drives (which can be OK also).

Unfortunately, according to the manual, the specific model number at the link has an LFU suffix so will only accept three phase input. He would need one with a model number having an NFE (single phase input) or NFU (single or three phase input) suffix.

The number of Instruction Manual pages of !WARNINGs! really cracks me up. I got bored and stopped counting after 8!!!

[Stephen Cherry]

Unfortunately, according to the manual, the specific model number at the link has an LFU suffix so will only accept three phase input. He would need one with a model number having an NFE (single phase input) or NFU (single or three phase input) suffix.

The number of Instruction Manual pages of !WARNINGs! really cracks me up. I got bored and stopped counting after 8!!!

Alan- as for all well documented products, there are plenty of documents:

http://www.hitachi-america.us/suppor...ngle-Phase.pdf

There are others that tell how to use external rectification, etc. This would get rid of the need for uprating to a 10 hp drive for a 5 hp motor.

[David Kumm]

I've been using the Hitachi LFU series for years with single phase input so it does work. Dave

[Alan Schaffter]

I've been using the Hitachi LFU series for years with single phase input so it does work. Dave

They make mention of that in the manual, but say to call tech support. Since the input is rectified to DC anyway before it is converted to 3 phase, I think many, if not most three phase VFD's can probably run on single phase if the input circuits have the require capacity. It is probably rarely discussed in the high horsepower VFD manuals, because most end users of bigger machinery have three phase available/already running the machinery on 3 phase.