Just want to say hello, this is my first post as i just came across this awesome site. Hope this is in the right section.
I recently installed a temporary setup for a large construction site, as the local utility is behind schedule, so the equipment we have may sound hokey but this is all we have to work with for a few weeks until the utility supplies the 600V service required
1. 425 MW generator - 480v output.
2. 1000KVA 480-600V Step up Autotransformer Wye-Wye (this equipment has no nameplate, but all coils common to X0 and someone painted on the side (480/277, 600/347)
3. New 600V CDP supplying for now, a 600 to 480 step down delta-wye transformer to feed the crane being erected.
With a few smart minds together, we decided to supply the 480-600V autotransformer with standard three-phase, without the neutral, from the 480V generator. The neutral bar on the generator, is tied to the ground bar on the generator. The autotransformer is fed with teck 2 350/mcm teck cables, and the two #3's in the teck(from the gen to x-fmr) are tied to the ground bar.
At the autotransformer, we supplied the 480V from the gen, and bonded the feeder grounds (#3's within the teck i just mentioned) to a bonding lug tied to the chassis of the autotransformer. Next we pounded a 10' ground ground rod, and tied it to the X0 of the autotransformer(w a 2/0 bare), and then to the chassis of the x-fmr. We then brought a 2/0 from the x-fmr chassis to the CDP and then from there, standard install out to the crane x-fmr(delta-wye) 600-480, and the XO is grounded from a ground plate beneath the crane. An equipment bond is also supplied within a PVC from the CDP to the crane x-fmr.
Hope im not rambling, but basically, i have read something, that suggests the feed to the auto-xfmr should supply a neutral, which of course is bonded, as well as the secondary being bonded, otherwise excessive voltages may occur on the secondary.
Will the setup i have installed function properly, or should i have brought the generator neutral to the autotransformer as well? If that is the case, should i have brought my system ground(from ground rod) to the generator first?
In our opinion, this setup should work fine, and has been tested OK without load to be working ok.
Any suggestions are welcome, this install is only temporary for a few weeks untill we can supply 600V straight from the utility. I am just concerned that once the crane puts a load on the system, we could have an imbalance, or perhaps (excessive voltages, as the book about the auto-xfmr suggested).
Hope this is clear.
Joe
I recently installed a temporary setup for a large construction site, as the local utility is behind schedule, so the equipment we have may sound hokey but this is all we have to work with for a few weeks until the utility supplies the 600V service required
1. 425 MW generator - 480v output.
2. 1000KVA 480-600V Step up Autotransformer Wye-Wye (this equipment has no nameplate, but all coils common to X0 and someone painted on the side (480/277, 600/347)
3. New 600V CDP supplying for now, a 600 to 480 step down delta-wye transformer to feed the crane being erected.
With a few smart minds together, we decided to supply the 480-600V autotransformer with standard three-phase, without the neutral, from the 480V generator. The neutral bar on the generator, is tied to the ground bar on the generator. The autotransformer is fed with teck 2 350/mcm teck cables, and the two #3's in the teck(from the gen to x-fmr) are tied to the ground bar.
At the autotransformer, we supplied the 480V from the gen, and bonded the feeder grounds (#3's within the teck i just mentioned) to a bonding lug tied to the chassis of the autotransformer. Next we pounded a 10' ground ground rod, and tied it to the X0 of the autotransformer(w a 2/0 bare), and then to the chassis of the x-fmr. We then brought a 2/0 from the x-fmr chassis to the CDP and then from there, standard install out to the crane x-fmr(delta-wye) 600-480, and the XO is grounded from a ground plate beneath the crane. An equipment bond is also supplied within a PVC from the CDP to the crane x-fmr.
Hope im not rambling, but basically, i have read something, that suggests the feed to the auto-xfmr should supply a neutral, which of course is bonded, as well as the secondary being bonded, otherwise excessive voltages may occur on the secondary.
Will the setup i have installed function properly, or should i have brought the generator neutral to the autotransformer as well? If that is the case, should i have brought my system ground(from ground rod) to the generator first?
In our opinion, this setup should work fine, and has been tested OK without load to be working ok.
Any suggestions are welcome, this install is only temporary for a few weeks untill we can supply 600V straight from the utility. I am just concerned that once the crane puts a load on the system, we could have an imbalance, or perhaps (excessive voltages, as the book about the auto-xfmr suggested).
Hope this is clear.
Joe
