Machine Riddle No.16 - Energy savings regarding
We are consuming 50,000 Wh per day with 50 Hz 435 V , But when we reduce the frequency to 49 Hz , conumption will reduce to 2000 Wh

#1
Tue, February 17, 2009 - 19:42
The consumption of industrial power network depends of rotation speed of rotary machines, for example the mechanical output of fans is proportional with cube of their rotation speed. The simplified form of the most commonly used fan laws include.

•CFM varies directly with RPM
CFM1/CFM2= RPM1/RPM2

• SP varies with the square of the RPM
SP1/SP2= (RPM1/RPM2)2

•HP varies with the cube of the RPM
HP1/HP2= (RPM1/RPM2)3

Indeed, we front to saving of energy (Undesirable reduction of consumption) with decreasing of system frequency. Of course as you know according to electrical basic conceptions, the power consumption are independent of frequency just in ohmic consumers (in sinusoidal conditions).Also we must not forget the measuring errors of energy meters due to voltage or frequency variation. Generally displayed consumed energy with induction type energy meters is lower of actual amount when they front of frequency or voltage decreasing( by comparison their rated parameters); because crawl torque which considered for overcoming of friction is according to rated system voltage and frequency.