I have a customer that is wanting to convert some newer upgrades of a grain operation into 3 phase. Currently all that is available is a 400 amp single phase 120/240 service. Now in the past we have considered installing a 3 phase service but it has proven to be more costly considering this is a seasonal operation. Taking that into consideration, I believe that at this point, it is wiser to itstall a phase converter for the time being.
Can anyone give me some leads on some calculations to determine what I will need to install. I will be operating a 25HP, a 7.5HP and a 15HP, respectively at the same time. What I need to determine first is what the sigle phase load will be while these are running. There will be other single phase 240VAC loads running at the same time also but I am mainly concerned at what this new load will be.
The Roto-Phase is a motor/generator which creates a 3rd phase through it's rotation. They work quite well for years without problems, but that being said Reno is right, the VFD is a much better product especially if you are on any sort of demand charge billing. The price of VFD's is good and they are readily available. I would install the VFD.
That being said, I have many 20 plus year old Roto-Phase sites that just keep plugging along and they will not be replaced until something dies.
I recommend TVSS protection on either installation.
We had an extensive thread on this subject [Hill-billy saw miller [SP] /2003?] on various single to three phase options, including running big three-phase motors with a donkey motor etc, quite a few years back. If memory serves me right, aren't phase converters required to be rated at about double the expected demand?
Last edited by Alan Belson; 06/05/0908:49 AM. Reason: spelling error
Phase converters are outclassed by VFD's, or frequency drives. Single phase in, three phase out - and with added features like soft start and speed control.
Agree. Also, they are easy to size, by FLA, located on the nameplate. No moving parts and no maintenance other than a good vacuuming every so often. VFD's are much less money that a rotary converter, and easily installed and set up.
I understand that VFD's are easier and less expensive but in this situation, there will be 5 new 3 phase loads added. So, wouldn't I need 5 VFD's or not?
If they are all motour load and they are running the same time or not ? if not sometime it cheaper to get RPC instead of VSD's depending on motour size But there is a major gothca almost all VSD are rated for one motour only so that something you have to think about it
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
5 VFD's or not? You ask as though that's a bad thing.
I bet you find that none of the three phase loads need to run at full speed - and that each has a different 'sweet spot.' In that instance, a drive for each unit is a real bonus. You also have enhanced reliability; one bad unit will not affect the other loads.