Energy Efficiency Improvement through Installation of Cyclic Load Energy Saver | SEA Energy Audit
Installation of Cyclic Energy Saver
Under loading of motor is a viable case of electrical energy consumption of motive load. We
identified in the industrial utility equipment having motor with starting characteristic of star - delta features having rating 45 KW and loading percentage below 60%. Intelligent systems are available as retrofit to extract the loss of energy under heading “Unloading”.
System Description: Cyclic Load Energy Saver saves power on Induction motor when it runs with partial load or No-load i.e. below 65% of full load. It is Horse Power proportional to Torque, which in turn is proportional to square of the voltage. When the motor runs with partial load (say below 60%), actually t requires the minimum load torque but since we are to supply the full Voltage maximum torque is produced that is the reason it doesn’t require that much torque for the corresponding low loads. Hence the unit converts the motor to Star
mode and supplies the required low torque only. Normally in star mode the motor can take 35 to 40% of the full load due to the reduction of voltage applied to the motors.
a. The magnetizing current is greatly reduced.
b. The motor operates with best maximum power factor due to reduction in logging current.
c. Since the current is also reduced I2R losses are greatly reduced.
The above constitutes the saving of power normally the applications are like compressors, press etc., runs with variation of loads that’s run below 65% and as well as full load. Hence the power can be saving on the motor when the application runs with low load.
Basic Principles of Energy Savings on Induction Motors
Normally Induction motor Horsepower is related as
H.P = 2πNT where T=Torque N= speed
H.P ∝ T i.e Speed is constant as N P.F
H.P ∝ V (voltage applied to the motor)
Thus motor H.P is proportional to the square of the voltage .It means that at maximum capacity (H.P max.) it requires V max (V=rated voltage).
So when the motor is operating at lower H.P than its rated voltage applied to the motor can be reduced.
As the voltage applied is reduced the current drawn is also reduced and Power = 1.723 VI cosϕ As ‘V’ and ‘I’ are reduced there is a reduction in power and hence energy savings.
Where Energy Can Be Saved
Energy saving is possible on Induction motor (with Delta to Star controllers) when it operates at loads lower than 60% of its full load. General Industrial application will have change of loads like:
a. Gradually changing loads (with respect to time).
b. Cyclic loads (example Compressors, chillers, and presses). These applications will have unloading and loading periods. During the non-compression or non-pressing periods load on the motor will be very low (around 30 TO 40%) hence high energy saving are possible.
Operating Principle of Cyclic Load Energy Saver
During the partial load or no load period the motor is supplied with 400/440 v as that much power is not required in that load condition .So by reducing the voltage applied during partial load periods power can be saved. Normally motors run in Delta mode i.e. full load voltage is applied to the motor. So by making the motor run in star mode during these no load periods only 1/ √3 times the line voltage is applied which reduces the power input to the motor.
Advantages of The Cyclic Load Energy Saver
The following are the best advantages of the Cyclic Load Energy Saver:
a. Improvement in PF: When the motors are operating at lower loads than it’s rated it will have poor power factor due to excessive magnetizing current for that particular load and poor efficiency at lower loads. When the motors are operating with Cyclic Load Energy Saver at lower loads the motor is made to operate in star mode in these loads and hence there is a reduction in applied voltage (1/ √3VL) to the motor and correspondingly Induction motor is reduced and hence reduction in relative current. Due to the reduced intake of reactive current the P.F of the motor is maximized and motor operates with maximum efficiency.
b. Reduced KVARH: By using delta to star converters, the reactive current taken by the motor during lower loads is drastically reduced and hence there is a saving in reactive power and energy over a period of time. The reactive energy is taken as the base (KVARH) for the calculation of Average P.F of the industry and customers are penalized for the consumption of more reactive energy slightest reduction for P.F by 0.01 below the fixed they are penalized. Hence Reduction in Reactive power consumption benefits the customer by substantial amount.
c. Reduced M.D: Due to the reduction in applied voltage with Cyclic Load Energy Saver there is a full current taken by the motor and improvement in P.F.
d. Power Savings: Due to the reduction of V.I there is a power saving during the star mode operation periods. Due to the reduced V, energy losses are reduced which accounts for energy savings