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


Voltage drop due to Phase shifting transformer

Voltage drop due to Phase shifting transformer

Voltage drop due to Phase shifting transformer

Although there is no inrush current drawn by the motors operated with VFD's, what about the Inrush current drawn by the phase shifting transformers? Does starting of new VFD with already running VFD, create significant voltage drop because of the Inrush of the phase shifting transformer? I'm concerned about the momentary voltage dip which may trip the running VFD.

RE: Voltage drop due to Phase shifting transformer

'It depends'

How stiff is your supply? If you have big drives on a small supply transformer and you're on the end of a long high impedance line then you'll quite possibly have problems. If the drives are small and you're on a large transformer fed directly from the transmission system then you probably won't. There are a myriad of possibilities in between the extremes. If you want a more definite answer you can model the network in software.

The DC link capacitors will provide some decoupling between the input and the output.

RE: Voltage drop due to Phase shifting transformer

Are you shutting off the power to the VFD, or just stopping it? You only get inrush on energization. If you're leaving power on to the VFD input, then there will be no inrush associated with starting another VFD.

If you're killing power to the VFD and phase shift transformer, stop doing that. It's not good for the drive to cycle power and they won't last as long.

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!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close