×
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!
*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

VRT

thread797-308548

VRT

VRT

(OP)
Good day all. I'm trying to understand how a variable reactance transformer works. I have a vacuum furnace that uses the VRT for heating element control and there are 4 high current diodes up in the power supply and I'm trying to understand they keep blowing. These VRT's are controlled with a Variable transformer (rheostat)and what is happening is, the 125VAC output from the SCR to these variable transformer's becomes 260VAC and destroys the control board for the SCR Pack. Hopefully this is enough information. I would like to know about the VRT's because without knowing what to expect I don't know where to look. Thanks much for your time.
Replies continue below

Recommended for you

RE: VRT

VRT is probably the same thing as a Magnetic Aplifier, which is also known as a Transductor - not Transducer.

The control windings usually have a high number of winding turns and, therefore, a high voltage is induced in those windings. A series reactor is usually used to reduce that induced voltage so it won't kill the control board.

Check to see if there is any problem with that series reactor, with capacitors used to filter out the induced voltage and other components in the circuit.

Question: Has there been any changes made in the equipmet lately? Is it possible that the control windings have been reconnected with the wrong polarity? Check voltages with an oscilloscope - they shall cancel.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: VRT

(OP)
Yes, there is a reactor inside the power supply cabinet. I don't have any prints available that show me how or why these diodes are there. I'm assuming they are used as a blocker, right? I'm not sure what the reactor does let alone how to test it.

RE: VRT

You need someone that knows about that technology, then. Or change the system to something more modern. Magnetic amplifiers are not common these days.

The diodes are there for two reasons: To rectify and to self-magnetize the cores. Sometimes the outputs are combined to produce AC output and sometimes the DC is kept.

What power range do you have? Amps? Volts? Single phase or three phases?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

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


News
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