A 25kW 125V separately excited DC machine is operated at a constant speed of 3000rpm with a constant field current such that the open circuit terminal voltage is 125V.If the machine is operated as.1)A generator with terminal voltage=124V and terminal po

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Question 1 of 5

A 25kW, 125V separately excited DC machine is operated at 3000 rpm with a constant field current such that the open circuit terminal voltage is 125V. If the machine is operated as a generator with a terminal voltage of 124V and terminal power of 24kW, what is the speed?

Since field current is constant, back EMF is proportional to speed. Calculate armature current, then find internal voltage. Use voltage drop to calculate speed.
Question 2 of 5

Considering the generator scenario in question 1, what is the armature current?

Terminal Power divided by Terminal Voltage gives Armature current.
Question 3 of 5

Considering the generator scenario in question 1, what is the back EMF?

Back EMF is equal to Terminal Voltage + Armature Resistance Drop (Ia*Ra) . First find Armature resistance from Original Speed.
Question 4 of 5

A 25kW, 125V separately excited DC machine is operated at 3000 rpm with a constant field current such that the open circuit terminal voltage is 125V. If the machine is operated as a motor with a terminal voltage of 123V and terminal power of 21.9kW, what is the speed?

Armature current is calculated using terminal power and voltage. Since flux is constant, the generated EMF is directly proportional to speed and proportional to terminal Voltage - Armature Drop. Then Use the calculated results from generator question to find Ra.
Question 5 of 5

Considering the motor scenario in question 4, what is the armature current?

Armature current is calculated using terminal power and voltage.
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