Frequency converters or AC drives use frequencies much lower than fixed speed controllers. However, frequency converters can significantly reduce energy usage, thereby saving production costs. Frequency converters use AC motors to control the pumps and fans in the system without the use of valves and dampers that are traditionally used to control constant speed motors, but which are sources of significant energy loss. Frequency converters can create the same energy flow without the need for high pressure and power required to regulate flow.
One of the energy saving advantages of frequency converters is the ability to adjust fan and pump speeds. The ability to easily adjust the speed of fans and pumps is a benefit in itself. If the fan only needs to run at half speed, the power requirement can be significantly reduced. These adjustments are made based on the current load requirements. Since a frequency converter can be connected to multiple motors, adjustments can also be synchronized. Synchronized deceleration and acceleration distribute the load more evenly and reduce losses. All of this can be done without braking, further optimizing energy usage. Other adjustments can change the voltage frequency ratio to ideal current, minimizing loss in the motor. They can also match the voltage in multiple motors and transfer loads from one to another. Further synchronization of the system, using software with frequency converters, can improve communication between drivers to increase efficiency.
Variable frequency drive energy savings also reflect when frequency converters increase the power factor of the system, energy usage is more efficient. A higher power factor means that the system uses more supplied energy in production mode rather than losing it in waste form. Variable speeds also prevent excessive consumption of electricity. Different speeds can gradually accelerate the motor, avoiding peaks and eliminating some high peak demand costs.
Of course, there are also other less direct factors that show variable frequency drive energy savings. For example, if a frequency converter does not have a transformer, it can be smaller and lighter. This means less heat is generated and there is no need for air conditioning. Another option in some frequency converters is actually energy regeneration, which can be turned around and used in the system or sold as excess.