In this Article we are going to discuss 2 devices other than power factor correction capacitors that can save you money on utility bills and make your power factor better.
How to improve power factor
The following devices and equipment are used to improve the power factor.
- fixed Power Factor Correction Capacitors
- synchronous capacitor
- stage progress
Fixed Power Factor Correction Capacitors
The load on most industrial and power systems is inductive, consuming lagging currents and reducing the power factor of the system. For the purposes of power factor improvement, static capacitors are connected in parallel to devices operating at lower power factors.
These static capacitors provide a leading current that (generally or roughly) neutralizes the lagging component of the load current (ie the main component neutralizes or cancels the lagging component of the load current). Therefore, the power factor of the load circuit is improved.
These capacitors are installed near large inductive loads such as induction motors and transformers to improve the power factor of the load circuit for system improvement or efficiency.
Power factor improvement by the static capacitor and synchronous capacitor
Here suppose a single-phase induced load with lagging current (I) and a load power factor of Cosθ.
Capacitor (c) is connected in parallel with the load. Here, current (Ic) flows through the capacitor and is 90° ahead of the supply voltage (note that the capacitor supplies the main current, i.e. in a purely capacitive circuit, the current is the supply voltage. It is 90° ahead of the current, i.e. the voltage is 90°, which is behind the current). The load current is (I). The vector combination (I) and (Ic) is (I’), which lags behind a voltage θ2 as shown in Figure 3.
Angle θ2 Cosθ1). Therefore, the load factor is improved by the capacitor.
Also, note that the circuit current after the power factor optimization will be lower than the current of the lower power factor circuit. Before and after power factor improvement, the active component of the current is the same in the circuit because the capacitor only removes the invalid component from the current. Also, the active power (in watts) will be the same before and after the power factor improvement.
Features:
Capacitor banks have many advantages over other methods of improving power factors.
- Low constant capacitor loss
- No moving parts, less maintenance
- Works under normal conditions (such as normal weather conditions)
- No foundation is required for installation
- Lightweight and easy to install
Cons: Disadvantages:
- The stationary capacitor bank has been used for a short period (8 to 10 years)
- As the load changes, the capacitor bank must be turned on or off. This causes a switching mutation in the system.
- If the rated voltage rises, it may cause damage.
- If the capacitors are damaged, repairs will be expensive
Synchronous capacitor
When a synchronous motor operates without load and is over-excited, it is called a synchronous capacitor. When the synchronous motor is over-excited, it is supplied with a leading current and acts as a capacitor.
If a synchronous capacitor is connected across the supply voltage (in parallel), then the main current will flow and the passive component will be partially removed, improving the power factor. Synchronous capacitors are commonly used in large industries to improve the power factor.
Features:
- Long life (about 25 years)
- high reliability
- Gradual adjustment of power factor.
- No maintenance compatibility
- Obstacles can be removed easily
- Not affected by harmonics.
- Less maintenance (only regular bearing grease required)
Cons: Disadvantages:
- Due to its high price (high maintenance cost), it is used by most of power users.
- Since the synchronous motor does not have a self-starting torque, an additional device must be used for this operation.
- makes noise
Develop stage
A phase leader is a simple alternating current inductor connected to the main shaft of the motor and operating in the motor’s rotating circuit to improve the power factor. Phase advances are used to improve the power factor of induction motors in the industry.
The induction motor stator windings consume lagged current that is 90° out of phase with the voltage, which results in a lower power factor for the induction motor. When the rotation of the excitation amp is excited by an external AC power source, there is no effect of the excitation current on the stator windings. Therefore, the power factor of the induction motor is improved. This process is done by Phase Advancer.
Features:
Since the excitation amp rotation is provided at slip frequency (fs), the delayed kVAR (power reactive component or reactive power) drawn by the motor is sufficiently reduced.
A phase drive machine is easy to use if the use of synchronous motors is not acceptable.
Disadvantage:
- Phase Advancer is not economical to use for engines below 200 hp. (about 150 kW)
- The improved power factor in single-phase and three-phase star and delta connections
- Improving the power factor of a three-phase system by connecting a capacitor bank
