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Why does a DC motor have a higher starting current?
Answer: The starting current is high as there is no back EMF or counter EMF present in the armature circuit because atstarting counter EMF is zero. It’s armature has very less resistance due to this it need more current at starting time. Hence DC starters are used to limit the starting current ofmotor.
Why do motors take high current?
Probable causes of high current with load include mechanical overload, excessively high magnetic flux densities and, less frequently, an open rotor. An error in winding data that results in lower-than-design-level magnetic flux also can cause high current with load.
Why does DC motor sometimes run too fast when under loaded?
Explanation: As the field resistance increases the speed decreases. Explanation: For armature voltage control, armature current is increased so as to reduce speed below base speed. In field control flux is reduced so the speed would be above base speed.
Why DC motor has higher speed than shunt motor?
In a series wound DC motor, the armature and field windings are connected in series, and the current through them is equal: Itotal = Ia = If. Like a shunt motor, as a load is applied to a DC series motor, the motor speed decreases, which reduces the back EMF and increases the net voltage.
Why does a DC series motor produce high torque?
Like a shunt motor, as a load is applied to a DC series motor, the motor speed decreases, which reduces the back EMF and increases the net voltage. However, in a series wound motor, the increased voltage causes both the armature and field currents to increase. This allows the series motor to produce very high torque on startup, for short durations.
What causes a motor to have a high no load current?
The most common causes of high no-load current after a motor is rewound are incorrect winding data and stator core damage. Incorrect winding data that increases the magnetic flux levels as compared with design levels will result in increased no-load current.
What happens when motor runs with lower current compared to?
Rated current is the highest capacity motor can operate at however due to varying load requirements motors never always operate at max load thus it saves energy as KWh are reduced. For constant high loads, motors operates almost at its rated current. , former British Electrician and Radio Ham.
What makes a d.c.motor a self-regulating machine?
makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load. Back e.m.f. in a d.c. motor regulates the flow of armature current i.e., it automatically changes the armature current to meet the load requirement.