ECN Forum Forums General Topics of the Trade General Discussion Area Machine hook up - 400v

JBD, it did say something about it being series rated.. or something, never seen that before on a panel, what do they mean by that?

Looks like I may need a transformer, The customer hasn't ordered the machine, he might get a different brand. He was checking with me if the correct hookup was there.

The 400-volt rating comes from the current European standard for 4-wire wye systems which was introduced a few years ago.

Britain had standardized on 240/415, whereas many other European countries had adopted 220/380. The 230/400 nominal rating was adopted as a "midway" standard for the whole of Europe.

You'll certainly need a transformer to hook up, as 480V with its tolerances is much too high.

And yes, PE is Protective Earth -- The equipment grounding conductor in American parlance.

Since the feeder conductors size and size of the OC protection hasn't been determined, could the "22.8 max amp available" mean that the calculated load of existing circuits allows for a 22.8A load of new circuitry can be added to the panel?

steve

stamcon, That 22.8a is too low, there are 60a breakers in them for the A/C's

aldav,
I'd suggest using the 'search' feature of this site to look up the following terms: 'series rating', 'available short circuit current', 'SSCR'. You will find lots to read up on.

In a nut shell, when you have a short circuit, the current flow is limited by the characteristics of the supply transformer, the circuit up to the point of the fault, and possibly any motors connected to the system that could regenerate power into the fault. The circuit breaker itself does _not_ limit the current flow significantly. It is the job of the circuit breaker to _interrupt_ this current flow. Available fault current is generally much greater than the continuous rating of the loads served; in residential applications with 100A services, fault current requirements of 2500A to 10000A are quite common.

If the short circuit current flow is too high, then the circuit breaker will _fail_. The current that a breaker is capable of interrupting is one of the ratings of the breaker, just like voltage or trip current. The breaker must be rated to interrupt the available fault current.

A 'series rating' is an exception to this general rule. Generally you have multiple breakers in series, eg. the main breaker at the service, followed by a breaker supplying a feeder to a panel, followed by a branch circuit breaker in the subpanel. The 'series rating' permits you to use specific combinations of upstream and downstream breakers, where only the upstream breaker is rated for the available fault current. To use a 'series rating' you are limited to using those _specific_ breaker combinations that have been tested. You need to evaluate the feeder as well as the panel that you are looking at to select a suitable branch circuit breaker.

-Jon

Acme makes a 15KVA transformer to step down from 575v 3ph primary side to 460v sec side. If I apply 277/480v pri side, supposed to get about 404v out sec side, Acme says.

If it is a 575:460V step down transformer, and you use it with an input of 480V, then the output will be 384V.

Additionally, if it is rated for 15KVA at 575V input and you use it with 480V input, then it will only have about 12.5KVA of capacity.

Finally, you should consider using 'buck-boost' transformers. These are auto-transformers rather than isolating transformers, where the KVA rating of the transformer only needs to be the output current times the _difference_ between supply and output voltage. You could adjust the 480V supply to the desired 400V output, at 15KVA on the output, with as little as pair of 1KVA transformers in an open delta connection...however for your application SOLA appears to recommend 3 of their 1KVA transformers in and 'auto-wye' configuration. See http://www.solaheviduty.com/products/transformers/BuckBoost/index.html and go through their 'selection steps'

-Jon