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Siemens Building Technologies Building Technologies Variable Frequency Drives VFD Basics.

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Presentation on theme: "Siemens Building Technologies Building Technologies Variable Frequency Drives VFD Basics."— Presentation transcript:

1 Siemens Building Technologies Building Technologies Variable Frequency Drives VFD Basics

2 Siemens Building Technologies Building Technologies What is a VFD? A Variable Frequency Drive is like the throttle on a car - It adjusts the speed of an HVAC fan or pump motor, based on demand, to save energy and prolong motor and mechanical component life Without a VFD, an HVAC fan or pump motor is either 100% ‘on’ or 100% ‘off’ A VFD eliminates the initial power surge and mechanical shock of switching the motor from ‘off’ to 100% ‘on’ A VFD conserves energy when an HVAC control systems senses that a fan or pump motor can meet heating or cooling needs by running at less than 100% power

3 Siemens Building Technologies Building Technologies Electric Motor Facts Electric motors account for more than two-thirds of all energy used in industry 63% of the energy consumed is linked to air & liquid flow A typical 50HP industrial motor, with an efficiency of 90%, costs over $25,000 to operate continuously over a year.

4 Siemens Building Technologies Building Technologies Other 17% Ventilation & Cooling 52% Lighting 31% Energy Usage in Office Buildings More than half the energy consumed by AC motors powers air conditioning equipment. Electrical energy costs are often the largest expenditure for building owners. Reducing energy demand and improving the working environment of a building are main objectives of facility managers. The principle reason for using VFDs is to reduce energy costs.

5 Siemens Building Technologies Building Technologies Why Use VFDs for HVAC Applications? Improved Energy savings Simplified motor control panel design Temperature regulation & comfort Monitoring Reduction in Mechanical component stress Damper commissioning Cabling Main power supply capacity Peak demand System components Noise

6 Siemens Building Technologies Building Technologies Energy Savings Comparison Potential energy savings using a VFD vs. modulating flow with a damper Flow Rate (%) Input Power (%) Damper SED2 VFD Ideal Fan Control Energy Saving Potential

7 Siemens Building Technologies Building Technologies How Does A VFD Work? It changes the speed of an AC HVAC fan or pump motor by adjusting or varying the frequency and voltage. For comparison, a DC motor speed is adjusted by only varying voltage. Typical frequency adjustment range in HVAC applications is from Hz AC. A VFD is wired in series between main power and motor. A Bypass is added to “Bypass” the VFD and run on main line power so HVAC operation is not interrupted if the VFD needs servicing

8 Siemens Building Technologies Building Technologies How Does A VFD Vary the Frequency? Switches (IGBT’s) VFD Block Diagram Motor Main Power Rectifier Capacitor Motor A VFD, AC inverter, or electronic speed controller for AC motors converts the AC supply to DC using a rectifier (diode), then converts it back to a variable frequency by using a inverter bridge.

9 Siemens Building Technologies Building Technologies VFD Specifying Standard Features vs. The Options Game When specifying VFDs – Don’t play the "Options Game" – make sure you get the most standard features for your money! Make sure VFD installers are certified by the manufacturer to get the most out of the drives capabilities. Make sure the drives are specified with advanced features, such as an integral harmonics reduction capability. Get more. Specify Siemens.

10 Siemens Building Technologies Building Technologies Low harmonics design Small enclosure size Many standard features Reduces operating cost Low power losses/high efficiency Minimal effect on customer power Wide power range – from ½ to 125 HP Siemens SED2 VFD Advantages


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