Generally, Swinburne’s test is the most popular testing method of dc machine to determine losses and efficiency. Therefore, Swinburne’s test is only applicable for dc shunt and small series machines. … This drawback can be overcome by performing field test.
How do you test a DC shunt motor?
first test the field winding with a megohmmeter to check, that the winding has no short to the housing. Then check the current consumption of the field winding. If you can, start with a low voltage and rise it until you reach the nominal voltage. Look for the maximum current at the specification plate.
Why the field of a DC shunt motor should not be opened?
The shunt field must never be 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.
What are the limitations of field test?
Fewer demand characteristics if participants are unaware.
- Lack of control brings problem of extraneous variables.
- Difficult to replicate.
- Difficult to record data accurately.
- Ethical problems.
What are the testing methods of DC motor?
The main tests used for DC machines are: Open circuit test. Short circuit test. Load test.
What is load test on DC shunt motor?
The load test is conducted by applying a spring balance load to brake drum of machine. By tightening the belt over the pulley different load can be applied. The spring balance reading S1 and S2 are noted and the effective radius ‘r’ of the pulley is measured. Efficiency of the motor=output power/input power.
What is brake test on DC shunt motor?
Concept of Brake test:
It is a direct method to determine the efficiency of DC motor. It consists of applying a brake to a water-cooled pulley mounted on the motor shaft as shown in fig. The brake band is fixed with the help of wooden blocks gripping the pulley.
What will happen when the field of a DC shunt motor gets opened while the motor is running Mcq?
4. What will be the effect of opening of field of a DC shunt motor while motor is running? Explanation: In a DC shunt motor if supply for the field winding is cut down, the speed would dangerously increase in order to maintain the back emf of the motor.
What happens if the shunt field of a DC shunt motor opens during operation *?
As mentioned above if the field circuit is opened, the back emf will drop to zero. With full armature voltage applied this will cause a very large armature current to flow which should normally blow the fuses. While the field current decays the motor will speed up as if in a field weakening mode.
What would be happened if field winding of DC shunt motor is abruptly opened?
Answer: n d.c shunt motor if field winding supply is removed the motor back emf will drop to zero, hence the armature will draw more current to make up the emf. this results in blowing up of fuse.
How do you conduct a field test?
To field test an instrument, the researcher may strategically select a very small number of individuals, say 3-5 people, who have expert knowledge about the population and research topic to provide feedback on the appropriateness of the questions being asked and how the questions are being asked in relation to the …
What are the advantages and disadvantages of field tests?
What are the advantages and disadvantages of field tests? Advantages: easiest aerobic capacity test; useful for tracking progress. Disadvantages: not an accurate predictor for VO2max, nor ideal for elderly clientele.
Why is field testing important?
The Major Field Tests help you: meet requirements for accreditation and accountability initiatives and performance funding by measuring the effectiveness of your program. evaluate and inform teaching and learning, and pinpoint strengths and areas of improvement to strengthen curricula and student learning outcomes.