×
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

critical dc motor starter, any new technology?

critical dc motor starter, any new technology?

critical dc motor starter, any new technology?

(OP)
a turbine's lube oil feed to its bearings has an "emergency DC oil pump".  The urgency in its use requires a starter that is failsafe, relaible and can achieve maximun acceleration with out damaging motor and battery bank.  the batterys are nominally 125 or 250VDC and the size is around 50 HP.

the current technology is energized timers that dropout to remove two resistors about every second to achieve full speed in 3 seconds.

The question; Is there modern technology that can control the inrush current to achieve the same starting times (and be failsafe)  

RE: critical dc motor starter, any new technology?

Modern technology may be a PWM drive to the DC motor or an inverter drive to an induction motor.
The most reliable may be the inverter-induction motor combination. No brushes and sealed bearings will make it a very low maintenance solution.
Define "Fail safe".

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: critical dc motor starter, any new technology?

(OP)
"defined failsafe"

this area is on the edge of my understanding, so that is why I've asked
the question of a "modern" starter for a turbine's emergency bearing oil pump (EBOP) was asked of me today while discussing the OEMs recommendation from 1970 to replace starters that used energized with deenergized to start relays with the OEMs claim of improved reliablity and failsafe design.

Since the last "new" steam turbine I've been on was in the early 90's I was wondering if any thing has changed from that design.  I do not have any plans to devolpe a design given the consequencies   

RE: critical dc motor starter, any new technology?

Hi byrdj,

The old resistor timestarter design is offers bomb-proof reliability and if suitably constructed is capable of surviving very severe overload conditions without failing. I'd always use the old-fashioned bar & shaft type contactors which cost a lot more than the typical AC-3 rated block contactors but are immensely tolerant of heavy switching. Semiconductors can't offer this level of survivability in an economically viable package. The benefits of semiconductors would probably be felt more in a frequent switching role, which doesn't really apply to emergency pumps.

A correctly designed timestarter will ultimately perform an across-the-bars start if the motor is 'tight' and won't accelerate with the starter resistors in circuit. This draws a very high current and may damage the commutator, and usually results in dropping every sensitive load fed from the turbine battery, but if you really need the oil pump in anger then very little else matters. Sacrificing a fews tens of thousands on a wrecked pump and motor is great value to save a multi-million pound turbine.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: critical dc motor starter, any new technology?

I am with scotty. I have seen even the latest steam turbines have the 'old-fashioned' timed out resistors type of starting for emergency DC lube oil pumps. My dad designed one such system for a 210 MW STG in 80's and it is still going strong.

Some poer stations even have gravity fed oil supply (Overhead tanks in the turbine hall) to the bearings as an redundancy.  

Muthu
www.edison.co.in

RE: critical dc motor starter, any new technology?

(OP)
thanks for the replies, it was that i realized it has been a long time since i saw what was current technology.
 

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