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TheRedDevil18
- 408
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For the locked rotor test I have these values,
P1 = 620W
Stator line voltage = 32V
Stator line current = 8.4A
To calculate active power/phase,
Po = (P1+P2)/3
But I don't have P2, Is P1 maybe equal to P2 ?
TheRedDevil18 said:Is P1 maybe equal to P2 ?
jim hardy said:i doubt it - that only happens at power factor 1.0
These show why.
http://www.Newtons4th.com/wp-content/uploads/2010/03/APP014-3-Phase-2-Wattmeter-Explained.pdf
http://educypedia.karadimov.info/library/2-Wattmeters method.pdf
Is this a lab ? Using those links you could calculate what P2 should read , then go back to the bench and see how close you came.
TheRedDevil18 said:then what is VL and IL
jim hardy said:What you measured on the voltmeter and ammeter.
TheRedDevil18 said:If I use VL = 32V and IL = 8.4A and Wa = 620W
620 = 32*8.4*cos(30+∅)
cos(30+∅) = 2.31
But that can't be true
Yeah, I think the wattmeter reading might be wrong. Will have to check it up in the lab again.jim hardy said:P1 reported 620 watts with 32 volts and 8.4 amps - something looks fishy there.
TheRedDevil18 said:Yeah, I think the wattmeter reading might be wrong. Will have to check it up in the lab again.
Thanks
jim hardy said:i didnt do anything, but thanks for the feedback.
8.4 amps is the current measured where ? If on your 5 amp ammeter, the CT is being overworked and likely is introducing undue phase shift... and so is the wattmeter's current coil..
Labs teach us more through serendipity than through the intended lesson.
Like Thoreau's Bean Field.
old jim
That's Good news... ThanksTheRedDevil18 said:The actual current measured on the ammeter was 4.2A, but the CT ratio is 2:1 so 4.2A*2 = 8.4A
An induction motor locked rotor test is a type of test used to determine the starting current and starting torque of an induction motor. It involves temporarily locking the rotor of the motor and then applying a specific voltage to the stator winding to measure the current and torque produced.
The locked rotor test is important because it helps determine the maximum current that an induction motor can draw when starting and the maximum torque that it can produce. This information is crucial for selecting the appropriate motor for a specific application and ensuring the motor does not overheat or become damaged during start-up.
The locked rotor test is performed by temporarily disconnecting the rotor of the motor and then connecting the stator winding to a voltage source. The voltage is slowly increased until the current reaches its maximum value, and the corresponding voltage and current readings are recorded. The torque can then be calculated using these readings.
Performing a locked rotor test helps ensure the proper functioning of an induction motor and can prevent costly damage or downtime. It also provides valuable information about the motor's starting characteristics, which can be used to optimize its performance and select the appropriate motor for a specific application.
Yes, there are potential risks associated with the locked rotor test, such as electrical hazards and mechanical hazards. It is important to follow safety protocols and use the correct equipment when performing this test to prevent accidents and injuries.