HOW CAN YOU ECONOMIZE
A great deal of money is spent annually to achieve savings in production methods, improved plant efficiency and optimum lighting arrangements; essential in the highly competitive world of industry today. However, poorly managed energy supplies result in unnecessary, and avoidable wastage. Power factor correction is the established method of reducing electricity costs in industry and commerce.
You can eliminate waste in electricity consumption by improving your power factor and saving up to 20% on your electricity costs.
This could also help you to increase your output without the need to install new cables or extra supply capacity.
The good news is that it costs you nothing to find out how to do this because we are offering you a FREE power factor check!
What is Power Factor Correction?
Most loads on an electrical distribution system fall into one of three categories; resistive, inductive or capacitive. In your own plant, the most common is likely to be inductive. Typical examples of this include transformers, fluorescent lighting and AC induction motors. Most inductive loads use a conductive coil winding to produce an electromagnetic field, allowing the motor to function.
All inductive loads require two kinds of power to operate:
Active power (kwatts) - to produce the motive force
Reactive power (kvar) - to energize the magnetic field
The operating power from the distribution system is composed of both active (working) and reactive (non-working) elements. The active power does useful work in driving the motor whereas the reactive power only provides the magnetic field. The bad news is that you are charged for both!
The objective, therefore, should be to reduce the reactive power drawn from the supply by improving the power factor.
If an AC motor were 100% efficient it would consume only active power but, since most motors are only 75% to 80% efficient, they operate at a low power factor. This means poor energy and cost efficiency because the Regional Electricity Companies charge you at penalty rates for poor power factor.
By installing capacitors to improve your power factor you could SAVE MONEY on your electricity bill.
Additional potential benefits include:-
Reduction of heating losses in transformers and distribution equipment
Longer plant life
Stabilized voltage levels
Increase in capacity of your existing system and equipment
Improved profitability
What do I have to do to save money? Simply contact our Van Rijn Electric office and we will arrange for an engineer to carry out a FREE power factor survey. This will be done quickly, with no interruption to your operations and with absolutely no obligation on your part. We shall then be able to advise you of the savings you can achieve which could be as much as 20% of your current electricity bill.
Power Factor Correction, How does it work?
Power Factor correction is applied to circuits which include induction motors as a means of reducing the inductive component of the current and thereby reduce the losses in the supply. There should be no effect on the operation of the motor itself.
An induction motor draws current from the supply, that is made up of resistive components and inductive components. The resistive components are:
1) Load current.
2) Loss current. and the inductive components are:
3) Leakage reactance.
4) Magnetizing current.
The current due to the leakage reactance is dependant on the total current drawn by the motor, but the magnetizing current is independent of the load on the motor. The magnetizing current wilt typically be between 20% and 60% of the rated full load current of the motor. The magnetizing current is the current that establishes the flux in the iron and is very necessary if the motor is going to operate. The magnetizing current does not actually contribute to the actual work output of the motor. It is the catalyst that allows the motor to work property. The magnetizing current and the leakage reactance can be considered passenger components of current that wit[ not affect the power drawn by the motor, but wilt contribute to the power dissipated in the supply and distribution system. Take for example a motor with a current draw of 100 Amps and a power factor of 0.75 The resistive component of the current is 75 Amps and this is what the KWh meter measures. The higher current will result in an increase in the distribution losses of (100 x 100) /(75 x 75) = 1.777 or a 78% increase in the supply losses.
In the interest of reducing the losses in the distribution system, power factor correction is added to neutralize a portion of the magnetizing current of the motor. Typically, the corrected power factor will be 0.92 - 0.95 Some power retailers offer incentives for operating with a power factor of better than 0.9, while others penalize consumers with a poor power factor. There are many ways that this is metered, but the net result is that in order to reduce wasted energy in the distribution system, the consumer will be encouraged to apply power factor correction.
Power factor correction is achieved by the addition of capacitors in parallel with the connected motor circuits and can be applied at the starter, or applied at the switchboard or distribution panel. The resulting capacative current is leading current and is used to cancel the [aging inductive current flowing from the supply.
Capacitors connected at each starter and controlled by each starter is known as "Static Power Factor Correction" white capacitors connected at a distribution board and controlled independently from the individual starters is known as "Bulk Correction".
Bulk Correction. The Power factor of the total current supplied to the distribution board is monitored by a controller which then switches capacitor banks I a fashion to maintain a power factor better than a preset limit. (Typically 0.95) Ideally, the power factor should be as close to unity as possible. There is no problem with bulk correction operating at unity.
Static Correction. As a large proportion of the inductive or tagging current on the supply is due to the magnetizing current of induction motors, it is easy to correct each individual motor by connecting the correction capacitors to the motor starters. With static correction, it is important that the capacitive current is less than the inductive magnetizing current of the induction motor. In many installations employing static power factor correction, the correction capacitors are connected directly in parallel with the motor windings. When the motor is Off Line, the capacitors are also Off Line. When the motor is connected to the supply, the capacitors are also connected providing correction at all times that the motor is connected to the supply. This removes the requirement for any expensive power factor monitoring and control equipment. In this situation, the capacitors remain connected to the motor terminals as the motor slows down. An induction motor, white connected to the supply, is driven by a rotating magnetic field in the stator which induces current into the rotor. When the motor is disconnected from the supply, there is for a period of time, a magnetic field associated with the rotor. As the motor decelerates, it generates voltage out its terminals at a frequency which is related to it's speed. The capacitors connected across the motor terminals, form a resonant circuit with the motor inductance. If the motor is critically corrected, (corrected to a power factor of 1.0) the inductive reactance equals the capacitive reactance at the tine frequency and therefore the resonant frequency is equal to the tine frequency. If the motor is over corrected, the resonant frequency will be below the line frequency. If the frequency of the voltage generated by the decelerating motor passes through the resonant frequency of the corrected motor, there will be high currents and voltages around the motor/capacitor circuit. This can result in sever damage to the capacitors and motor. It is imperative that motors are never over corrected or critically corrected when static correction is employed.
Static power factor correction should provide capacitive current equal to 80% of the magnetizing current, which is essentially the open shaft current of the motor.
The magnetizing current for induction motors can vary considerably. Typically, magnetizing currents for large two pole machines can be as low as 20% of the rated current of the motor while smatter low speed motors can have a magnetizing current as high as 60% of the rated full toad current of the motor. It is not practical to use a "Standard table" for the correction of induction motors giving optimum correction on all motors. Tables result in under correction on most motors but can result in over correction in some cases. Where the open shaft current can not be measured, and the magnetizing current is not quoted, an approximate level for the maximum correction that can be applied can be calculated from the half load characteristics of the motor. It is dangerous to base correction on the full load characteristics of the motor as in some cases, motors can exhibit a high leakage reactance and correction to 0.95 at full load will result in over correcting under no toad, or disconnected conditions.
Static correction is commonly applied by using one contactor to control both the motor and the capacitors. It is better practice to use two contactors, one for the motor and one for the capacitors. Where one contactor is employed, it should be upsized for the capacitive load. The use of a second contactor eliminates the problems of resonance between the motor and the capacitors.
Inverter. Static Power factor correction must not be used when the motor is controlled by a variable speed drive or inverter.
Solid State Soft Starter. Static Power Factor correction capacitors must - not be connected to the output of a solid state soft starter. When a solid state soft starter is used, the capacitors must be controlled by a separate contactor, and switched in when the soft starter output voltage has reached line voltage. Many soft starters provide a "top of ramp" or "bypass contactor control" which can be used to control the power factor correction capacitors.
Capacitor selection. Static Power factor correction must neutralize no more than 80% of the magnetizing current of the motor. If the correction is too high, there is a high probability of over correction which can result in equipment failure with sever damage to the motor and capacitors. Unfortunately, the magnetizing current of induction motors varies considerably between different motor designs. The magnetizing current is almost always higher than 20% of the rated full load current of the motor, but can be as high as 60% of the rated current of the motor. Most power factor correction is too tight due to the selection based on tables which have been published by a number of sources. These tables assume the lowest magnetizing current and quote capacitors for this current. In practice, this can mean that the correction is often less than half the value that it should be, and the consumer is unnecessarily penalized. Power factor correction must be correctly selected based on the actual motor being corrected. The Busbar software provides two methods of calculating the correct value of KVAR correction to apply to a motor. The first method requires the magnetizing current of the motor. Where this figure is available, then this is the preferred method. Where the magnetizing current is not available, the second method is employed and is based on the half Load power factor and efficiency of that motor. These figures are available from the motor data sheets.
For example: Motor A is a 200 KW 6 pole motor with a magnetising current of 124A. From tables, the correction applied would be 37KVAR. From the calculations, this would require a correction of 68.7 KVAR
Motor B is a 375KW 2 pole motor with a half toad efficiency of 93.9% and a half toad power factor of 0.805, the correction recommended by the tables is 44 KVAR white the calculations reveal that the correction should be 81.3KVAR
ASEA dry type power factor
A UL Listed state-of-the-art product by the largest manufacture of low voltage capacitors in the world
Why Use Capacitors?
Most electrical systems service a wide variety of inductive loads including motors, transformers, and 
fluorescent lighting. One characteristic of inductive loads is that they utilize a winding in order to operate. When energized, this winding produces an electromagnetic field which enables the motor or transformer to function. The electrical power required to energize this winding is called reactive power. The other characteristic of inductive loads is that in addition to reactive power, they also require active power to actually perform the work. Without capacitors, the local power utility must provide both reactive and active power. The more reactive power required to set up the magnetic field, the more power (kVA) the utility must supply. Capacitors act as reactive current generators. With capacitors on line, then, this not only frees the utility from having to supply reactive power, but also frees the distribution system to carry more active power (kW).
fluorescent lighting. One characteristic of inductive loads is that they utilize a winding in order to operate. When energized, this winding produces an electromagnetic field which enables the motor or transformer to function. The electrical power required to energize this winding is called reactive power. The other characteristic of inductive loads is that in addition to reactive power, they also require active power to actually perform the work. Without capacitors, the local power utility must provide both reactive and active power. The more reactive power required to set up the magnetic field, the more power (kVA) the utility must supply. Capacitors act as reactive current generators. With capacitors on line, then, this not only frees the utility from having to supply reactive power, but also frees the distribution system to carry more active power (kW).Capacitors Save You Money!
Power factor ratings are a measurement of how effectively a plant uses electrical power. The higher the ratings the more effective the electrical power is being used and vice versa. Power factor correction capacitors can save you money in several ways!
As more and more utility companies are assessing penalty charges for low power factors, power factor correction capacitors eliminate these costly penalties.
Secondly, since all systems waste a certain amount of power through line losses in conductors, the reduction in current draw which results from the addition of capacitors reduces losses significantly, thus reducing the power bill. Finally, the addition of capacitors may prove a very favorable alternative to expanding the distribution system when additional capacity is required as less electrical power can be utilized more effectively.
ASEA Capacitors offer Numerous Technical Advantages
Self-Healing
"Self -healing" is a characteristic which is unique to metallized-film capacitors. All capacitors normally experience insulation breakdown as a result of the ~accumulated effect of temperature, voltage stress, impurities in the insulating medium, etc. When this happens in a non-metallized design, the electrodes are short-circuited and the capacitor ceases its production of reactive power. In an ASEA metallized-film unit, however, these individual insulation breakdowns do not mean the shutdown of the capacitor. The faults self-heal themselves and the capacitor continues operation.
Dry Construction
ASEA low voltage capacitors contain no free liquids and are filled with a unique non-flammable granular material called vermiculite. Environmental and personnel concerns associated with leakage or flammability of conventional oil-filled units are eliminated; and kvar for kvar, vermiculite filled units weigh 30% to 60% less than their oil-filled counterparts.
Thanks to the highly efficient polypropylene dielectric used in ASEA capacitors, total losses, including those across discharge resistors, are less than 0.5 watts/kvar which is much less than conventional designs.
correction capacitors...
The IPE (internally Protected Elements) Sequential Protection System
The unique IPE Sequential Protection System provides the ultimate system for safety and protection including:
• Dry, self-healing design
• IPE (internally protected elements)
• Dry, nonflammable vermiculite filler
At the end of the element's life, the dielectric deteriorates so that self-healing becomes somewhat a continuous process progressing outward from the middle of the element. Every element in an ASEA capacitor is provided with a non-self -healing outer winding to reliably and selectively disconnect the element at the end of its life.
