×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

want to know about working of soft starter for motor control?

want to know about working of soft starter for motor control?

want to know about working of soft starter for motor control?

(OP)
can someone tell me about the working and design of soft starter panels. if somebody has some material on it please let me know.

RE: want to know about working of soft starter for motor control?

A soft start utilizes SCR's to provide variable voltage (at fixed frequency) to a motor during starting. The voltage is ramped up to full voltage over a time period that is usually user variable. More sophisticated soft starts use a closed loop current ramp instead of a fixed time ramp, meaning that the drive would be set to limit starting current to motor FLA (for example) and would accelerate as fast as possible at that current. Most modern soft starters use a bypass contactor that engages once the motor is up to speed. This eliminates efficiency losses in the soft start and, more importantly, allows for a smaller and less expensive design as the soft start does not have to be rated for continuous duty.

Soft starts are usually applied when a (relatively) large motor is run on a (relatively) small power system. In other words, if a single motor's full load power is equal to 25% or more of the rated capacity of the transformer feeding it, then unacceptable voltage sag results when the motor is started at full voltage. A soft start will eliminate this problem and will allow motor full load to equal transformer full load. (25% figure given above is a ballpark number, if others in the forum have more specific info please post it)

As well, soft starts may be applied to systems where it is desirable to reduce the mechanical shock of full voltage starting by gradually ramping up to speed.  

Finally, soft starts may be used on large motors (>1000hp) to increase the # of allowable starts per hour. Heating is the limitation for # of starts in large motors. By limiting starting current you reduce the heating significantly and may obtain more starts per hour.

I hope this helps.

RE: want to know about working of soft starter for motor control?

Suggestions:
1. To include y-delta starters under soft starting
2. To include other power electronic principles in addition to the above posting, e.g. motor variable speed drives.
3.  Visit
http://www.manufacturing.net/magazine/dn/supplements/motion/soft.htm
for more info on soft starting.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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