If both are used to calculate the efficiency for a DC motor/generator, then why don't we just use the Swinburne's test? For example it has a easier circuit. Is there (maybe) an advantage of one test over the other?
Electrical – the difference between the Hopkinson’s test and the Swinburne’s test for a DC motor/generator
efficiencytesting
Related Solutions
Efficiency for power supplies is most meaningful at full-rated load. Without a load, the output power is zero and therefore efficiency is meaningless. If you look at the data sheets of a lot of switching converters they'll show graphs of efficiencies versus various loads but they will never really small or zero power loads BUT they will always show full-load power efficiency.
Also when you make a circuit what are the major tests you need to perform and check? I mean like efficiency test, thermal test, Emc test, etc.
For a power supply, efficiency is important for a lot of designs and I always run a regulator circuit at full load at elevated temperatures (above what it can be expected to see) because, with little doubt or uncertainty, the most common failure of components is in power supplies. EMC can mean many things and I think that unless you are designing a power supply to be sold as a power supply, EMC testing would be done on the whole product.
I would also look for ripple voltage problems and instability issues on various loads.
When determining efficiency, keeping track of where the energy is going can be quite difficult. If the motor efficiency is 70 percent, the losses are 30 percent of the input. If you can only determine the input power and output power with a 95 percent accuracy, the actual input power could be 5% higher than measured and the actual output poser could be 5% lower than measured. That means that it is possible that the losses determined from input and output measurement may be up to 33% higher or lower than the actual losses.
With the thread and spool method, you must consider the energy lost in the friction of the mechanism and the potential energy converted to kinetic energy of the falling weight and the rotating mass.
What Chris Stratton suggests is essentially constructing a dynamometer using the motor as an absorber. The diagram below shows what is required. The trunion mounting system allows the absorber housing to turn freely by a few degrees to allow the scale to measure the force exerted by the arm extending from the housing. Torque is the force multiplied by the length of the force arm to the shaft center. Torque multiplied by speed is mechanical power.
Whether the motor is acting as a motor or a generator, a force is generated between the stator and rotor. The rotor force is transmitted or received through the motor shaft. The stator force is normally transmitted through the motor housing to the platform on which it is mounted. The grunion bearings permit the motor housing to rotate. The rotation of the motor housing is prevented by the torque arm. The torque arm is prevented from moving by the scale or force transducer that is connected between the arm and mounting surface.
Best Answer
Some of the notable differences between Hopkinson's and Swinburne's test include:
In Hopkinson's test we need a pair of both motor and a generator whereas in Swinburne's we need only one.
The temperature rise can be observed in Hopkinson's test because this test is done under full load conditions but since Swinburne's test is done in no-load conditions, we cannot observe the temperature rise.