10-05-2017, 12:35 AM
I randomly tested myself on power factors and failed. I'd forgotten how to add a series reactance to a resistance. So, sure, I'd forgot. I revised it again. You square the resistance value, square the reactance, add the total and then use the square root button. The square root of the sum of the squares was a rule I plain forgot. So I find I don't retain what I learned.
Here is the example in the book for anyone else who feeels rusty. A pure resistance of 75 R is to be added to 100 X reactance. Thus, 10000 + 5625 = 15625 the square root being 125 Ohms. Voltage is said to be 250 volts and current 2 amps. Apparent power would be 500 watts but the real power is 75 R times current squared 300 watts. Power factor will be 300/500 = 0.6 All of this I just revised and marine engineers also tend to do power factors. However, I'll probably forget it again. Anyway that is the rule I forgot: You don't just add the X and R but you square each value, add total and get the square root on the calculator. Maybe I should set myself imaginary questions.
Here is the example in the book for anyone else who feeels rusty. A pure resistance of 75 R is to be added to 100 X reactance. Thus, 10000 + 5625 = 15625 the square root being 125 Ohms. Voltage is said to be 250 volts and current 2 amps. Apparent power would be 500 watts but the real power is 75 R times current squared 300 watts. Power factor will be 300/500 = 0.6 All of this I just revised and marine engineers also tend to do power factors. However, I'll probably forget it again. Anyway that is the rule I forgot: You don't just add the X and R but you square each value, add total and get the square root on the calculator. Maybe I should set myself imaginary questions.
