The idea is that the magnetic field of the device reacts with the external magnetic field. If the current is reversed, the magnetic field would also be reversed, and the reading would be the opposite.
Difference between field controlled and armature controlled is that field control is open loop and armature current is closed loop.
DC shunt motor can be reversed by changing the polarity of either the armature coil or the field coil.
.The magnitude of the voltage and current of both the armature and shunt field coil. To decrease the speed when the load is increasing then increase the shunt field current while decreasing the armature voltage or current. To increase the speed while the load is increasing then increase the armature current while decreasing the shunt field current. The decreasing and increasing of these currents and voltages can be done by connecting a variable resistor in series or parallel with each of the armature and/or shunt field coil.
In shunt motors, the armature voltage ( E ) changes when the field rheostat is varied because altering the resistance in the field circuit affects the field current and, consequently, the magnetic flux produced by the field winding. When the field rheostat is decreased, the field current increases, leading to a stronger magnetic field and a higher back electromotive force (EMF) generated in the armature. This results in a change in the armature voltage, as the increased back EMF reduces the net voltage across the armature. Conversely, increasing the field resistance weakens the magnetic field, reducing back EMF and allowing the armature voltage to rise.
The direction of the force that drives the machine is determined by the relative directions of the field and the armature current. By reversing the direction of both field and the armature current, the direction of the resulting force stays the same; you have to reverse the direction of one or the other; not both! Prove it for yourself, by applying Fleming's Left-Hand Rule (for conventional current flow); reverse the direction of both your first finger (field) and your second finger (armature current), and you thumb (direction of motion) will end up pointing in the same direction!
The direction of the force that drives the machine is determined by the relative directions of the field and the armature current. By reversing the direction of both field and the armature current, the direction of the resulting force stays the same; you have to reverse the direction of one or the other; not both! Prove it for yourself, by applying Fleming's Left-Hand Rule (for conventional current flow); reverse the direction of both your first finger (field) and your second finger (armature current), and you thumb (direction of motion) will end up pointing in the same direction!
The idea is that the magnetic field of the device reacts with the external magnetic field. If the current is reversed, the magnetic field would also be reversed, and the reading would be the opposite.
If the direction of the current in an electromagnet is reversed, the direction of the magnetic field surrounding the electromagnet will also reverse. This change in direction will affect the polarity of the electromagnet, causing its north and south poles to switch.
The motor needs the current and magnetic flux to create motion The magnetic field is created by field winding where as armature carries the current resulting into the rotation of armature
Difference between field controlled and armature controlled is that field control is open loop and armature current is closed loop.
armature reaction means when load is added to the armature then current is passed through armature conductors then in armature creates flux. It is demagnetize and cross magnetize the main field flux. in other ward it is effect of armature field on main field.
DC shunt motor can be reversed by changing the polarity of either the armature coil or the field coil.
The terms 'shunt' and 'armature' apply to a particular type of d.c. motor, in which the field windings are connected in parallel with the armature windings. 'Shunt' is an archaic term for 'parallel', so the term 'shunt', in this context, means that the field winding is connected in parallel with the armature winding. The terms 'shunt current' and 'armature current', then describe the currents flowing in the shunt winding and armature winding, respectively.
When a current flows through an electric bell, it creates a magnetic field that causes the armature, attached to a spring, to be attracted towards the electromagnet. This movement causes the armature to strike the bell, producing a ringing sound.
One of the role of the armature in the DC motor is to carry the current that is crossing the field. By carrying the current crossing the field, it creates the shaft torque in the rotating machine.
DC shunt motor can be reversed by changing the polarity of either the armature coil or the field coil.