Contents
What is mechanical losses in DC motor?
Mechanical losses can be occurred due to the effects of the machines. These losses are separated into two losses namely bearing friction & windage. These kinds of losses can occur at the moving parts within the dc machine. The air in the DC machine is also called as windage losses.
What is constant loss in DC shunt generator?
(b) Magnetic Losses (also known as iron or core losses), Hysteresis losses or Magnetic losses occur due to demagnetization of armature core. This losses are constant unless until frequency changes. Eddy current losses are due to circular currents in the armature core.
What is the effect in a DC shunt motor?
When voltage is applied to a DC shunt motor, the armature draws current sufficient to produce a strong magnetic field, which interacts with the magnetic field produced by the shunt windings, causing the armature to rotate.
What will happen when the field of a DC shunt motor gets opened while the motor is running?
If the shunt field suddenly opens while the motor is being operated under full-load conditions, only a small voltage due to the residual magnetism of the pole pieces will be induced into the armature. Current will increase considerably. The magnitude of this current may be sufficient to burn out the motor.
What are the losses in DC generators?
There are four internal losses that contribute to lower efficiency of a DC generator.
- Copper losses.
- Eddy-current losses.
- Hysteresis losses.
- Mechanical losses.
What will happen if load of DC shunt motor is reduced?
the speed of motor will be reduced. the armature current will reduce. In case of DC shunt motor, flux is practically constant as field is parallel to the armature. If load is reduced then the speed of motor will remain almost constant because the field current remains almost constant.
What is the no load loss of a DC shunt motor?
No-load losses of a DC Shunt motor consist of constant losses Wc and a small amount of armature copper loss Waco. Mechanical losses. To estimate constant losses one has to conduct (i) Swinburne’s test and (ii) Armature resistance Ra measurement test.
How to calculate armature copper losses in DC shunt motor?
For a motor on no load, power input to the armature is the sum of the armature copper losses and the above losses. In the circuit diagram, Power input to the armature = V*Ia watts. Armature copper losses = Ia2*Ra watts V*Ia – Ia2*Ra = (A + C)N + (B + D)N W/N = (A+C) + (B+D)N.
How much copper does a shunt wounded field lose?
This loss is changeable & mainly depends upon the quantity of the dc machine load. In a shunt wounded field, practically the field copper loss is stable and it donates 20% to 30% to full- load losses. The resistance of brush contact contributes toward the copper losses. Usually, this kind of loss comes under armature copper loss.
What is the emf of a shunt DC machine?
The armature resistance drop is 0.3V so the armature emf = 229.7V. The no-load power input is therefore found from the 3A current and 229.7V armature emf – which would correspond to the rotational loss. The shunt field would take 2A, so the armature has the remaining 3A. The armature resistance drop is 0.3V so the armature emf = 229.7V.