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Why DC motor starting current is very large?
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 is DC motor more efficient?
They run faster than induction motors due to the fact that the speed is reduced by the slip of the asynchronous motor. In fact, the DC motor is 30% more efficient than AC motors due to the secondary magnetic field being generated from the permanent magnets rather than copper windings.
What determines the power of a DC motor?
Power. The power of a motor is the product of its speed and torque. The power output is greatest at about half way between the unloaded speed (maximum speed, no torque) and the stalled state (maximum torque, no speed). The output power in watts is about (torque) x (rpm) / 9.57.
What is the advantage of DC motor?
Good speed control DC motors offer highly controllable speed. By changing the armature or field voltage it’s possible to achieve wide speed variation and with this level of controllability, DC motors offer the precision required by a wide range of industry applications.
Is a DC or AC motor more efficient?
Which Motor Is More Powerful: AC or DC? AC motors are generally considered to be more powerful than DC motors because they can generate higher torque by using a more powerful current. However, DC motors are typically more efficient and make better use of their input energy.
What is disadvantage of DC motor?
Disadvantages Of DC Motor Maintenance cost is high and increased operation due to the presence of brushes and commutator. Due to sparking at brush DC motors cannot operate in explosive and hazardous conditions. As the speed increases, the shaft gets vibrated and the armature gets damaged.
Why do you need a DC motor for a DC drive?
With shunt field control a DC motor can achieve speeds above base speed and produce a constant horsepower capacity. Armature voltage control is used for speeds below base speed, giving us a constant torque capacity. One advantage of using a DC motor with a DC drive is that regenerative energy can be fed back into the mains.
What is the speed of a DC motor?
Usually this is specified as the speed in rotations per minute (RPM) of the motor when it is unloaded, or running freely, at its specified operating voltage. Typical DC motors run at speeds from one to twenty thousand RPM.
What is the current rating of a DC motor?
Thus current ratings are often given when the motor is stalled. At this point it is drawing the maximum amount of current and applying maximum torque. A low voltage (e.g., 12 Volt or less) DC motor may draw from 100 mA to several amperes at stall, depending on its design.
What makes a brushless DC motor different from an AC motor?
Brushed DC motors depend on a mechanical system to transfer current, while AC and brushless DC gear motors use an electronic mechanism to control current. The brushed motors have a wound armature attached to the center with a permanent magnet bonded to a steel ring surrounding the rotor.