Smart Motor Control
Electric motors are the single biggest consumer of electricity. They account for about two thirds of industrial power consumption and about 45% of global power consumption, according to a new analysis by the International Energy Agency. The efficiency of electric motors is an important topic we need to tackle.
The SMC provides motor control for numerous types of motor applications. We mainly focus on motor control for HVAC systems and Kitchen Ventilation Systems. For HVAC systems, we have VFDs for chiller compressors, condenser water pumps, chilled water pumps, cooling tower fans, condenser coil fans, supply/return fans, and parking garage exhaust fans.
VARIABLE FREQUENCY DRIVES
What is a VFD?
A type of Adjustable Speed Drive used in electro-mechanical drive systems to control an AC motor’s speed and torque by varying the motor’s frequency and voltage. It adjusts the speed of a fan or pump motor based on demand to save energy by up to 20% and prolong the motor's and mechanical component's life. Without a VFD, a fan or pump motor is either 100% ON or 100% OFF. A VFD eliminates the initial power surge and mechanical shock from switching the motor from OFF to ON.
How does a VFD work?
A VFD converts incoming AC power to DC, which is inverted back into three phase output power. Based on speed set-points, the VFD directly varies the voltage and frequency of the inverted output power to control motor speed. A VFD changes the speed of an AC fan or pump motor by adjusting the frequency. The typical frequency adjustment range is from 10 - 60Hz AC. A VFD is wired in series between the main power and the motor. A bypass is added to “bypass” the VFD and run on main line power so operation is not interrupted if the VFD needs servicing.
How does a VFD save energy?
A VFD offers the greatest opportunity for energy saving when driving variable torque loads, such as pumps and fans. This is because horsepower varies as the cube of speed, and torque varies as the square of speed, for these loads. For example, if the motor speed is reduced by 20%, the motor horsepower is reduced by a cubic relationship (.8X.8X.8), or 51%, by the Affinity Law. Because of these potential savings, utilities often offer subsidies (rebates) to customers investing in VFD technology for their applications.
Soft Starters VS. VFDs
Soft Starters and VFDs will reduce the incoming current rush and consequent electric spikes, which are not only expensive electrically, but are also damaging to motor windings, bearings, and the motor itself. Thus, both Soft Starters and VFDs reduce wear and electrical consumption, as well as increase life for these components. However, what a VFD does that a Soft Starter can not, is run a motor at whatever speed(s) is(are) preselected and programmed. While a VFD can vary the speed at which its motor is run, a motor on a Soft Starter can only run at full speed (60 Hz) because Soft Starters can only control the starting current.
Buildings’ chiller plants often operate at less than a full load for more than 95% of their operating hours and are designed to handle unexpected overloads. These traditional, constant-operating systems use energy unnecessarily.
Variable frequency drives (VFD), also known as variable-speed drives or adjustable-speed drives, are a key technology used to reduce energy use and cost. They offer an attractive energy conservation measure where there is a need to vary the flow in distribution systems.
HVAC systems often lack the ability to regulate the motors and fans that ventilate a space in response to environmental changes like the weather or building occupancy. Instead, California's building code requires the air damper to be fixed open wide enough to ventilate to the demands of peak occupancy, no matter how many people are actually inside the building. In addition, the supply fan is required to constantly re-circulate air.
Kitchen Demand Control Ventilation (KDCV)
Food Service Facilities have the highest energy cost per square foot in the commercial building sector. Within food service facilities, HVAC systems account for 29% of the energy consumption.
KDCV system is designed to reduce fan energy consumption by slowing the exhaust and makeup air fans whenever full speed is not needed.