Constant losses
Those losses in a d.c. generator which remain constant at all loads are known as
constant losses. The constant losses in a d.c. generator are:
(a) iron losses
(b) mechanical losses
(c) shunt field losses
Losses mean energy losses, which cost money, and most people like to know how much a machine is going to cost to run.
Dc shunt motor is a constant flux and constant speed motor . So that it is used in centrifugal pumps ,machine tools ,blowers and fans etc.
By installing the varialble resistor in the circuit,the constant dc voltage would change .
The slip rings are the most important brush in DC machine.
Dc chopper is a static device which converts constant dc source to variable dc.
The condition for maximum efficiency of a d.c. machine is that VARIABLE LOSSES must be equal to CONSTANT LOSSES i.e., variable losses = constant losses..
How to calculate iron losses in dc machine
in a dc machine core losses occur both in stator and rortor but stator core losses are negligible as compared to rotor core losses because in stator constant dc flux is given and the statot conductor is stationary so there are no eddy losses and as the flux is stationary there are no hysteresis loassses also but in rotor armature winding is placed so here alternating field is induced which cuts the rortating conductors of rotor thereby inducing eddy as well as hysteresis losses fo any more info. contact zombie
Losses mean energy losses, which cost money, and most people like to know how much a machine is going to cost to run.
Dc shunt motor is a constant flux and constant speed motor . So that it is used in centrifugal pumps ,machine tools ,blowers and fans etc.
1. swinburne's test is economical since power required to test a large machine is very small (i.e.,)no load input power. 2.The efficiency of the machine can be predicted at any load, since constant losses are known. 3.This method enables us to determine the losses and efficiency without actually loading the machine
By installing the varialble resistor in the circuit,the constant dc voltage would change .
What motor is NOT suitable for use as a DC machine?
The slip rings are the most important brush in DC machine.
In DC or direct current, the flux is constant. AC or alternating current is variable.
Dc chopper is a static device which converts constant dc source to variable dc.
swinburne's test on dc shunt machine is to predetermine the efficiency of the dc machine , but it is not accurate it is just like estimation of efficiency of dc shunt machine when it is run as a motor and a generator............................