Which DC motor has got maximum self-loading property? Explanation: A differentially compound DC motor, flux reduces so sharply at small increase in load at higher values of load. It is advisable that motor should not be used beyond some load value, as it may damage itself by self-loading. 5.
Which DC motor has got maximum self relieving property?
Which DC motor has got maximum self-relieving property? Explanation: DC series motor develops large starting torque initially and slow down with increase in load and so get automatically relived from heavy excessive load. Thus, DC series motor is called as self-reliving machine. 6.
Which DC motor has tendency of load instability?
Because the field decreases with a load increase, a differential compound motor has a tendency for load instability.
Which DC motor has poorest speed control?
1. Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit.
What are the 3 types of DC motors?
Types of DC Motors. There are 3 main types of DC motor that are available:- Series, Shunt and Compound. These terms relate to the type of connection of the field windings with respect to the armature circuit.
Why is the DC motor preferred over AC motor?
DC motors have the advantage of: higher starting torque, quick starting and stopping, reversing, variable speeds with voltage input and they are easier and cheaper to control than AC. AC motor advantages include: lower power demand on start and minimal maintenance.
What will happen if the back EMF of a DC motor vanishes suddenly?
What will happen if the back emf of a DC motor vanishes suddenly? Explanation: If back emf vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. If supplying unit didn’t trip down by this time, excess current in armature may heat up the armature. 3.
Why starters are used in DC motor?
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.
Which power is mentioned on a name plate of a motor?
Shaft output, speed, cosϕ and motor current can be taken from the nameplate. Efficiency and torque can be calculated on the basis of the nameplate information.
What is back EMF of dc motor?
The coil of a DC motor is represented as a resistor in this schematic. The back emf is represented as a variable emf that opposes the one driving the motor. Back emf is zero when the motor is not turning, and it increases proportionally to the motor’s angular velocity.
What controls the speed of a DC motor?
Thus, the speed of a DC motor can be controlled in three ways: By varying the supply voltage. By varying the flux, and by varying the current through the field winding. By varying the armature voltage, and by varying the armature resistance.
What is used to adjust the speed of a DC shunt motor?
The speed of DC shunt motor can be varied by varying the field current. As we increase the resistance R of the rheostat, the field current Ish decreases. So the flux φ decreases. This results in increasing the speed of the motor.
What will happen if DC motor is used without starter?
What will happen if DC motor is used without starter? Explanation: It would cause intolerably heavy sparking at the brushes which may destroy the commutator and brush-gear. Sudden development of large torque will cause mechanical shock to the shaft, reducing its life.
What are the 4 types of DC motor?
There are 4 main types of DC motors:
- Permanent Magnet DC Motors. The permanent magnet motor uses a permanent magnet to create field flux. …
- Series DC Motors. In a series DC motor, the field is wound with a few turns of a large wire carrying the full armature current. …
- Shunt DC Motors. …
- Compound DC Motors.
5 июл. 2017 г.
Which DC motor is best?
Series wound DC motors are best for applications that require high startup torque, without the need for speed regulation. 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.
Which is best AC or DC motor?
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.