Hi readers I hope you all doing great. In this post, we will have a detailed look at Compound Wound DC Motor or DC Compound Motor. This motor is called a compound since it comprises of both series and shunt windings. In this motor, the series field windings is linked to the armature windings in series combination, and shunt field winding link to the armature windings in field windings.
In this post, we will discuss its working types of operation and some other related factors. So let’s get started with DC Compound Motor.
Introduction to DC Compound Motor
- Compound dc motor comprises of the shunt as well as series field windings. The circuit of this motor can be seen in the below figure.
- The dot shown in the figure indicates the direction of current similar to the transformer. That means the current moving towards the dots indicates the positive MMF.
- If the current direction is towards the dots for both field windings due to the addition of these two flux high MMF is produced.
- This condition where two flu added to create a high value of MMF is called a cumulative compound.
- If the current direction is such that it moving towards the one field windings and away from second field findings then MMF decreases due to opposite direction flux crosses each other.
- If we apply KVL to the above circuitry. then we have.
VT = EA+ IA(RA+RS)
- The current equation for the compound motor is given here.
- The value of net MMF and shunt field current in this motor is given here.
Torque-Speed Characteristic of Cumulatively Compounded DC Motor
- In this motor, one part of flux has a constant value and the other is directly proportional to the armature current. Due to this the torque for the cumulatively compound motor has high value than shunt motor starting torque but less than the series motor starting torque.
- In simple words cumulatively compound dc motor provides the features of shunt and dc series motor in a single package.
- Such as similar to the series motor it offers a high value of starting torque and not become Overspeed when no load is exit similar to shunt motor.
- In the case of lightweight load linked to this motor series filed shows less effect so it operates like a shunt dc motor.
- With the increment in loads series winds become significant and its flux too so this motor shows features like the series motor.
- In the below figure the torque-speed characteristics of this motor can be seen.
Torque-Speed Characteristic of Differentially Compounded DC Motor
- In differentially compound dc motor shunt windings and series field windings flux cross each other.
- It shows that with the increment in load armature current increases and value of flux in the motor reduces.
- Due flux decrement speed of motor rises. This speed increment causes load increment that increases armature current and further flux decrement and further increment in speed.
- This consequence is that a differentially compound motor is not stable and becomes a runaway. This unstable behavior of motor is very dangerous than the shunt motor that is affected by the armature reaction.
- In the below figure the character’s curve of this motor is shown.
Application of Compound Dc Motor
- the common application of this motor are explained here.
- As this motor lift larger loads so it preferred in elevators.
- In shears and punches machines it used.
- As it provides high starting torque so used in stamping presses.
- It used in printing press machines.
- It used in steel rolling mills.
So that is a detailed post about Compound Dc Motor if you have any further query ask in the comments. Thanks for reading. Have a nice day.