As far as DC motors are concerned, the compound DC motors has all the advantages. But as far as comparison with AC motors there are a few disadvantages. Operation and maintenance cost of DC motors are expensive. DC motors unable to operate in hazard situation where spark occurs at the brush of the motor.
Why is a differentially compounded motor unsuitable for any application?
This speed increases causes anther increases in load, which further increases Ia , further decreasing the flux, and increasing the speed again. The result is that a differentially compounded motor is unstable and tends to run away. It is so bad that a differentially compounded motor is unsuitable for any application.
What are the disadvantages of the differential compound motor?
In fact, the polarities of the magnetic field of shunt winding and armature magnetic fields oppose each other. Note that This trait is not really desirable because the net flux produced is lesser than the main flux so, it does not find much of a practical application.
Why differentially compound motor is not used in industry?
Low torque results in a high speed, which further reduces the torque, and the motor becomes unstable even with a slight change in load. The differential compound motor cannot be used for any practical application due to its unstable behavior with even a slight variation of the load.
What are the characteristics of a cumulatively compounded DC motor?
In a compound motor, if series and shunt windings are connected such that series flux is in direction as that of the shunt flux then the motor is said to be cumulatively compounded. And if the series flux is opposite to the direction of the shunt flux, then the motor is said to be differentially compounded.
What type of compound motor connection should be avoided?
What type of compound motor connection should be avoided and why? The differential compound motor because it will stop and become a series motor.
Which type of motor has high starting torque?
DC motor has high starting torque.In a series motor the same current flows through the armature and the field winding.
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.
Which power is mentioned on a nameplate of a motor?
Which power is mentioned on a name plate of a motor? Explanation: Name plate of the motor shows rated values i.e. rated speed, rated current, rated voltage. It also shows output power available at shaft when all other quantities are set to rated values.
What is the most common uses of compound DC motors?
Compound wound motors are usually used where you need higher starting torque and relatively constant speed. The compound DC motors applications are in presses, shears, conveyors, elevators, rolling mills, heavy planners, etc.
What is difference between shunt and compound motors in after reverses the direction of rotation?
When the direction of rotation of a series or shunt motor is to be changed, either the field or the armature leads can be reversed. Many small DC shunt motors are reversed by reversing the connection of the shunt field leads. … When a compound motor is to be reversed, only the armature leads are changed.
How do you reverse the rotation of a compound DC motor?
The rotation of a compound-wound motor can be reversed by changing the direction of the current in the field or the armature circuit, ( 5). Since the series field coils must also be reversed if the shunt field is reversed, it’s easier to reverse the current in the armature only.
How many types of compound motors are there?
The types of compound excited DC motor are Short Shunt Motor, Long Shunt Motor, Differential Compound, Cumulative Compound.
What are characteristics of dc motor?
Characteristics of DC Motor means the relation(or graph) between different parameter like Armature Torque, Armature Current & Speed of the motor. There are three characteristic of DC motors which are: Torque speed characteristics. Torque current characteristics and.
What are the operating characteristics of dc motor?
DC Motor Characteristics
- Runs on DC power or AC line voltage with a rectifier.
- Operating speeds of 1,000 to 5,000 rpm.
- 60-75% efficiency rate.
- High starting torque.
- Low no-load speeds.
Why starters are required in a DC motor?
1. Why starters are required in a DC motor? … Explanation: Starting resistance of a DC shunt motor and DC compound motor is low. Well, that’s the reason why we use starters in a DC motors, in order to limit the armature current flowing through the armature and to protect machine circuitry.