×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

three phase low volts use?

three phase low volts use?

three phase low volts use?

(OP)
why are three phase low voltage power supplies used for outputs greater than 2kW or for a low output ripple?

RE: three phase low volts use?

(OP)
any input guys?

RE: three phase low volts use?

The rectifier in a three-phase unit outputs a voltage with only a few percent ripple and needs very little smoothing. The reason is that the three phases overlap so that the rectified voltage never goes to zero.

A single phase rectifier doesn't have that property. The voltage goes to zero 120 times/second (US) or 100 times/second (Europe). That's a lot of ripple. It can be smoothed out with capacitors, but ripple increases with load.

A three-phase unit has a constant, low ripple that is almost independent of load.

Gunnar Englund
www.gke.org

RE: three phase low volts use?

(OP)
so is that because of the phases being 120 degrees apart the sine wave doesnt go down to zero as one phase is going from full +ve to -ve the next one is just going to full +ve?

RE: three phase low volts use?

Yes, that's right. If you draw a diagram over the three voltages and then "fold" the negative ones up, you will get a pretty good picture of what a rectified three-phase voltage looks like.

Gunnar Englund
www.gke.org

RE: three phase low volts use?

(OP)
brilliant thanks

RE: three phase low volts use?

That and single phase is usually an outlet that can only supply 1,500W without extra hassles.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources