Since you know the power rating of the motor and the supply voltage, you can calculate the current required by the motor from the equation; P=VxI .
How do you calculate the starting current of a DC shunt motor?
Suppose you have a DC motor rated at 10 hp, 220 V and full load rated current of 25 A. The armature resistance is 0.5 Ω. Without a starter, when the power is applied to the motor, the initial current will be 220/0.5=440 A. This is 17.5 times the full-load current!
How do you find the field current of a DC shunt motor?
- When dealing with DC motors, sketch the circuit. You know Total Power PT = 11kW and Total Voltage VT = 220V. …
- The shunt field and armature are in parallel. You have the field resistance and the total voltage is applied across the field. …
- Apply KCL to determine Ia.
- Not asked, but from there you can calculate back-emf E0.
What is the formula of DC shunt motor?
The back EMF(Eb)= V-Ia.Ra
Thus the ratio of Eb/Φ remains almost constant, and the speed of the motor is almost constant with an increase of armature current with loading. Therefore, the DC shunt motor is a constant speed motor.
How do you determine the load current of a DC shunt motor at which the motor efficiency is maximum?
Equation (1) shows that the efficiency of a DC generator is maximum when those losses proportional to the square of the load current are equal to the constant losses of the DC generator. This relation applies equally well to all rotating machines, regardless of the type of machine.
Why is DC motor current so high?
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.
What is the starting current of a DC shunt motor?
For all practical practices to obtain optimum operation of the motor the armature resistance is kept very small usually in the order of 0.5 Ω and the bare minimum supply voltage being 220 volts. Even under these circumstance the starting current, Ia is as high as 220/0.5 amp = 440 amp.”
What is the principle of DC shunt motor?
Construction and Working Principle
The working principle of a DC Shunt Motor is, whenever a DC motor is turned ON, then DC flows throughout stator as well as the rotor. This current flow will generate two fields namely pole as well as the armature.
What are the characteristics of DC shunt motor?
Characteristics of a DC Shunt Motor:
- Speed-Armature Current Characteristic: …
- Torque-Armature Current Characteristic: …
- Speed-Torque Characteristic: …
- Break in Field Circuit of a DC Motor:
Why DC shunt motor is constant speed?
If the load on the motor increases armature speed reduces and thereby cause a reduction in the back emf. … Hence, a DC shunt motor always maintains a constant speed. Under no load condition, the back emf becomes nearly equal to the applied voltage.
What are the advantages of DC shunt motor?
Advantages of Dc shunt motor:
- The power supply of the DC motor is any way cheap.
- Shunt would motor able to runs at a predetermined speed.
- The speed of a dc shunt motor is sufficiently constant.
- Direct current machines can use for heavy industrial applications where the torque and speed wider range.
What is a DC shunt?
Direct current instrument shunts are used to extend the range of ammeters whenever the current to be measured is too large to be passed through the instrument–usually currents over 50 amperes. The shunt, therefore, is a diverter which is used to “shunt” the majority of the current around the indicating instrument.
Why DC shunt motor is started on no load?
For DC shunt motor the field resistance is high and armature resistance is low so the variation of flux is very less when rated voltage is applied to the motor and motor speed does not exceeds rated speed at no load. So we can start the DC shunt motor with no load.
Which power is mentioned on a name plate 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.