# DC motor circuits parameters.

Discussion in 'Homework Help' started by TheSpArK505, Nov 26, 2014.

1. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
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0
Hello everyone >>

For a motor circuit say a shunt circuit
@I want to know what's the input and what's the output?
@ also what quantities depend on what ?? for example the armature current or the armature induced voltage depends on what and the flux, speed, and field current???

Jul 18, 2013
10,867
2,528
There are many variables.
The shunt field current is directly dependent on the resistance of the field and the applied voltage.
The armature current is dependent on applied voltage, the load, and RPM of the armature, (Generated voltage).
When voltage is applied, the motor rotation generates a back EMF opposing the applied voltage, the armature will rotate to the point the back EMF almost equals the applied voltage.
RPM is determined by voltage, torque by current (armature loading or inertia).
Incidentally if you remove the field while the motor is rotating it will be in a run away condition and if not loaded, can destruct.
Max.

3. ### TheSpArK505 Thread Starter Member

Sep 25, 2013
92
0
ok..... is the torque of the load is caused by the armature movement>

and where is it's location in the circuit?

and if y can give me a link to a microscopic view of motors and it's parts and how they work.

Jul 18, 2013
10,867
2,528
If you look at the manuf. torque curve of a typical high quality DC motor, you will see the torque is usually maximum at zero RPM and is fairly flat up the rated RPM.
When you apply a voltage to a stationary motor the current is limited only by the resistance of the armature and the applied voltage, until the motor accelerates and generates a BEMF.
In an off loaded motor, the only load to overcome is the inertia of the armature, if an external load is present, then the current will initially be subsequently higher.
I will see if I have a link on record that may help explain it.
Max.

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Sep 25, 2013
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