Questions about DC Machines

Re: dc machines

U can refer ashfaq hussain book

Re: dc machines

AMITBOSEU can refer ashfaq hussain book

More details please!!!

Increase in flux decreases the speed but increases the torque. If torque is decreased by decreasing the field current the following sequences are found:

1. <a href="https://en.wikipedia.org/wiki/Counter-electromotive_force" target="_blank" rel="nofollow noopener noreferrer">Counter Electromotive Force</a> drops instantly, the speed remaining constant because of the inertia of heavy armature.
2. Due to decrease of EMF armature current I is increased because of I = (V − E)/R.
3. A small decrease of flux is more than counterbalanced by a large increase of I which means net increase of torque.
4. If torque increases the speed also increases.

If applied voltage is kept constant, motor speed has inverse relation with flux.
where:

• N = revolutions per minute .i.e. motor speed
• K = proportional constant
• R = resistance of armature (<a href="https://en.wikipedia.org/wiki/Ohm" target="_blank" rel="nofollow noopener noreferrer">Ohm</a>)
• V = electromotive force (<a href="https://en.wikipedia.org/wiki/Volt" target="_blank" rel="nofollow noopener noreferrer">Volt</a>)
• I = current (<a href="https://en.wikipedia.org/wiki/Ampere" target="_blank" rel="nofollow noopener noreferrer">Ampere</a>)
• Φ = flux (<a href="https://en.wikipedia.org/wiki/Weber_%28unit%29" target="_blank" rel="nofollow noopener noreferrer">Weber %28Unit%29</a>)

You will know it clearly by doing lab exercises perfectly..

You can find the answers in book-B.L.THEREJA

I can find answer in any electrical machine book like b.L.Thareja volume 2.