×
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

DC motor - Speed torque curve

DC motor - Speed torque curve

DC motor - Speed torque curve

(OP)

I beleive the speed torque curve of a DC motor is different from a AC motor. Why is this so?

Do any one have typical Speed torque curve of both DC motor and pump?

RE: DC motor - Speed torque curve

Have a read of any decent electrical machines text and you will find your answers.
  

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

RE: DC motor - Speed torque curve

The normal operating part of the speed/torque curve is very similar if you compare a DC and an AC machine. Speed drops a few percent when load increases from zero to 100 %.

There are different DC motor characteristics and different AC motor characteristics. But, in practical use, they can be regarded as almost identical.

It is only when you get above the break-down torque that they differ and have very different characteristics. As Scotty says, find a text-book and do some studying.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: DC motor - Speed torque curve

There are many DC motor types. But, usually, at least in our time, 4 types are most employed [for power actuation]:
Separate [independent] excitation, shunt excitation, series excitation and combined excitation.
For information only, the Torque-speed relations may be considered as follows:
Separate [independent] excitation or shunt excitation:
n[rpm] =Ua/(Ke*Phi)-Ra*Torque/(KT*Phi) –linear function
Ua=rotor voltage
Phi=magnetic flux
Ra=rotor resistance
Series excitation:
n=Ua/(K1*sqrt(Torque)-(Ra+Re)*K2- it is a hyperbole [aproximate]
The combined excitation characteristic is an intermediate curve.
For AC Induction Motor one may use this formula:
Torque=2*MaximumTorque/(s/sk+sk/s)
s [slip]=(nsynchron-n)/nsynchron
sk is the slip corresponding to maximum Torque.
See the attachment for illustration
 

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