hw7 - torque, using your expression for current. Although...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
EE321 Spring 2008 Homework 7 Problem 30 – Separately Excited DC Machine A separately excited dc machine has a armature resistance of 0.2 Ohms, a field resistance of 4 Ohms, L af of 200 mH. We wish to determine the currents (armature and field) in such a way as to achieve a torque of 2 Nm, while minimizing the loss. What should the armature and field current be ? What will the machine loss be at this point ? Problem 31 – Series Connected DC Machine Consider a series connected DC machine connected to an AC source with rms amplitude t V and radian frequency e ω . Assuming the speed is constant, compute the average torque in terms of r , t V , e , aa L , af L , ff L , a r , and f r . Note: the first part of this problem is to find the current, which can be done using phasor analysis. The second part of the problem is to find the average
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: torque, using your expression for current. Although this problem may seem strange at first, it is actually used in practice. This type of machine is commonly referred to as a universal machine (since it can be run from a dc or ac source), and is sometimes used in handheld tools such as corded variable speed electric drills. Problem 32 PM DC Machine Parameters When spun at a speed of 1000 rad/s, the open circuit armature voltage of a PM DC machine is 100 V. Next, the sped of the machine is reduced to 900 rad/s, and a 100 V source is applied to the machine terminals. The armature current is 20 A. What are the electrical parameters of the machine? Note: this is basically a slight variation of the procedure we considered in class....
View Full Document

This note was uploaded on 09/22/2011 for the course ECE 321 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.

Ask a homework question - tutors are online