With increasing torque load the armature tends to slow down; the motor draws more current to compensate, and if there is armature resistance the back emf generated by the armature falls to allow the increased current to flow, which causes the motor to settle at a lower speed.
The mechanical output power is the speed times the torque, and increasing the torque increases the power output provided the speed does not drop much.
If you think of a motor using a clock with the 12 and 6 being positive and negative polarity, a motor runs most efficiently (fewest amps) when operating as close to those points as possible. When you increase the load, the motor is slowed every so slightly, or maybe dramatically, and the further away from those poles it gets the more power it draws. It also has more output power which enables it to drive higher loads.
So a motor is always trying to get back to peak efficiency. If, under any load, it approaches the poles it will use less power, thus fewer amps.
When a motor is spinning it produces a back EMF which opposes the flow of current through the motor. At startup it is not spinning and there is no back EMF.
Basically when the load increases the armature current will decrease as the flux increases so the power output also decrease
as the load increases armature current decreases, because armature current is inversly proportional to the load given to a motor
armature
Increasing flux, torque of the dc motor will be increased and speed of the dc motor will be decreased as speed of the dc motor is inversely proportional to that of the flux and the torque of the dc motor is directly proportional to the flux.
To ensure that the Lathe machine's motor working properly, DC motor starter is added in which it used to protect motor against damage from: • short-circuit, • long term overload, • excessive starting current, and yet to made the operating speed of motor easily to be control by operator. During starting, the motor is not turning, hence there is no internal voltage .The internal resistance is very low and thus the current flow through is very high. This condition may cause damage to the motor Hence, a staring resistor is added in which connect in series with the armature to limit the current flow until the internal voltage of motor is increasing to do the limiting. In order to prevent losses as the speed of the motor is build up; the starting resistor should be removed
The field current of a dc motor provides the magnetic field that allows the motor to develop a torque when current flows through the armature..
With increasing torque load the armature tends to slow down; the motor draws more current to compensate, and if there is armature resistance the back emf generated by the armature falls to allow the increased current to flow, which causes the motor to settle at a lower speed. The mechanical output power is the speed times the torque, and increasing the torque increases the power output provided the speed does not drop much.
The starting current is high because when the motor is not rotating no back-emf is generated, leaving the starting current to be determined by the armature resistance, which should be low.
armature
Armature current is the current flowing in a motor's armature. The "armature" is another name for the coil (or coils) of wire which are on the motor's "rotor", which is the part that rotates inside its stator. (The "stator" is the fixed, non-rotating part of the motor.)
With increasing torque load the armature tends to slow down; the motor draws more current to compensate, and if there is armature resistance the back emf generated by the armature falls to allow the increased current to flow, which causes the motor to settle at a lower speed. The mechanical output power is the speed times the torque, and increasing the torque increases the power output provided the speed does not drop much.
If a DC series motor is started without load, the armature winding (winding that doesn't spin) current will be at a minimum, resulting in the motor going to maximum speed / runaway, which can cause things to fly apart. As Armature current increases, the speed of the motor will decrease. The armature current will be forced to increase / speed of the motor will be forced to decrease as more and more load is applied.
if there are magnets on the stator and the commutator is phased properly this is known as a permanent magnet dc motor the starting torque is dependent on armature current and the strength of the magnet the speed is directly proportional to the armature voltage a shunt motor needs the field energized for starting. more field more starting torque
commutator, armature
extra resistance is added in order to decrease starting current and improve starting torque
It isn't. It is only kept at maximum resistance when the motor is not running. That is done to limit the starting current.
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.
Yes! · To accelerate the motor to the rated speed · To limit the starting current in the armature to a safe value · To disconnect the motor in case of a supply failure or overload
To deliver the current to the rotating armature