# Siemens GenIV VFD question



## MDShunk (Jan 7, 2007)

That's for occasions where you use the VFD more like a soft start, then switch to utility 60hz when your VFD 60hz is in sync with the utility 60hz. Vice-versa when ramping back down. Used mostly on multi-motor applications where one VFD "Starts" multiple motors in succession.


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## MDShunk (Jan 7, 2007)

What's the horsepower and voltage anyhow? I'm just curious. I always thought synchronous transfer equipment was external to the drive. I didn't realize it was a built-in feature on some.


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## glen1971 (Oct 10, 2012)

MDShunk said:


> What's the horsepower and voltage anyhow? I'm just curious. I always thought synchronous transfer equipment was external to the drive. I didn't realize it was a built-in feature on some.


Thanks for the help!

It feeds a 2,300 volt 1,150 hp motor.. The drive that's coming out is an old Ross Hill..


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## MDShunk (Jan 7, 2007)

glen1971 said:


> Thanks for the help!
> 
> It feeds a 2,300 volt 1,150 hp motor.. The drive that's coming out is an old Ross Hill..


Ah. Medium voltage drives are out of my wheelhouse. Just wondering. Thanks.


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## JRaef (Mar 23, 2009)

GenIV (Generation 4) is just the latest version of the Siemens / Robicon "Perfect Harmony" MV drive. Robicon has almost always had a feature called "Synchronous Transfer" that allows you, as MDShunk said, to essentially use the VFD as a giant soft starter. So you ramp the motor up using the VFD functionality, but when you get to full speed, you "transfer up", which means you make the VFD output synchronize with the incoming line frequency and transfer the motor over to an across-the-line starter, then take the VFD off line, or recycle it for another motor in a multiplexed system. You have to synchronize the frequencies, otherwise when you connect the motor out of synch with the line, it blows things up, like the VFD outputs, and that's not good on a $300,000 VFD. So Transfer Up means going from VFD to A-T-L, then Transfer Down means going the other way, from running A-T-L back to having the VFD control speed.


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## glen1971 (Oct 10, 2012)

*Update...*

Well we got rid of the old Ross Hill on Monday and installed the new Siemens one this past week.. Put power to it on Friday and ran the motors yesterday.. Seemed to work pretty slick.. 
Nice lookin drive, but the only flaw that I could see is it seemed a little "tinny".. When we went to roll it into the building it stopped dead on the rollers.. I looked down and when they built it, they cut steel out of the base C-Channels to allow forks to pass through.. When they did that, the weight of the drive bowed the bottom portion of the steel.. Ever try moving a 12,000 lbs car with 2 flat tires? We finally got it into place and bolted down and were able to straighten the "steel" in a fairly short time.. 
Then we noticed the door handles were out of alignment... Checked with a bubble stick and everything looked good, but the upper half of the cabinet seemed twisted..Measured corner to corner and it was out about 1/2", but no sign of metal stress anywhere... 
The blower assembly frame was of a similar "tinny" construction, and that was an easier one to fix...


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