--------------------------------------------------------------------
I was watching a “factory made” segment yesterday about the
Tesla electric car. They said the car developed
450 hp. W H A T?? I
looked it up on Wikipedia. It said the
car developed 248 HP. That is still way too much for an AC motor. They said that the motor weighed only 70
pounds and was a 4 pole A.C. induction motor.
The stator looked to be about the same size as a G.E. 80 frame hermetic motor. The 80 frame stator core punchings weigh 10
pounds per inch of stack. A 9 inch stack
core would weigh 90 pounds and develop only 50 HP at 1800 rpm. (G.E.Spec) , that
is 5.55 hp per inch of stack. A 70 pound
stator would be 7 inches long and develop 38.88
hp at 1800 rpm. Then I looked at the Tesla motor speed. The dang thing turns at 14,000, (yes fourteen
thousand) RPM.
The plot thickens.
14000 rpm vs. 1800 rpm (STD 4 pole design synchronous speed) is a factor
of 7.77. 7.77 * 38.88hp = 302 hp. Factor in about 88 % efficiency and 8% slip
for the rotor “chasing” the field and you have 244 HP. This is close to the 248
hp claimed by the company. That entire
HP is gained through speed, not brute strength.
The automobile has a single speed, fixed gear
transmission. If the transmission is “fixed”,
then the motor speed is variable. The
problem is that an A.C. induction motor speed is not variable. The only way to vary the speed would be to
vary the frequency of the input voltage.
Now let’s calculate the actual CPS of the Tesla motor. 60/1800 = X/14,000. X = 466 CPS.
There was a three-cylinder Harnishfager diesel generator used on the Nike
Hercules missile system. The generator operated at 400 CPS, which was
considered the same as D.C. ----- No inverter required???
Someone is going to wonder why we have 200 HP motors the
size of a 55 gallon drum when we can get it from a motor the size of a 10 quart
bucket.
No comments:
Post a Comment