Adjustable Frequency Drive HVAC Application Fundamentals
COMMON TERMINOLOGY VFD (VARIABLE FREQUENCY DRIVES) AFC (ADJUSTABLE FREQ. CONTOLLER) ASD (ADJUSTABLE SPEED DRIVES) VSD (VARIABLE SPEED DRIVES) FREQ. DRIVE INVERTER DRIVE Inverter Duty Motors =?? = New motors meet NEMA MG 1, Part 31 = peak voltage of 1600 volts and a minimal rise time of 0.1 microseconds
Why Flow Control? HVAC systems are designed for worst case situations. Most of the time they have excess capacity. Controlling flow Saves energy Improves occupant comfort
Methods of Flow Control Air flow Inlet guide vanes Outlet dampers Variable pitch fan Adjustable speed Fluid flow Bypass valve (three way) Throttling valve (two way) Adjustable speed
Why Adjustable Speed? Energy savings System control Reduced maintenance Sound control
Why Adjustable Frequency Drives? Minimum maintenance High efficiency Easy retrofit Remote mounting Simple control Bypass capability
Cooling Tower & Fluid Cooler Fan Cooling Tower Cells Chiller Temperature Sensor Condenser Water Pump Cooling Tower Fan Drive
VAV AHU Supply Fan Outside Air Damper Supply Fan Conditioned Space Heating Coil Return Air Damper Cooling Coil Pressure Sensor Return Fan Relief Air Damper Supply Fan Drive
Secondary CHW (HW) Pump Secondary Chill Water Pump Chiller Air Duct Air Duct Air Duct Air Duct Differential Pressure Sensor Cooling Coil Cooling Coil Cooling Coil Cooling Coil Primary Chilled Water Pump Secondary Chilled Water Pump Drive
Smoke Extraction Outside Air Damper Supply Fan Conditioned Space Close this damper Return Air Damper Return Fan Reverse this fan Smoke Sensor Relief Air Damper Supply Fan Drive
CAV Fan & Clean Rooms Conditioned Space Supply Fan Air Filter Pressure Sensor Supply Fan Drive
Return Fan Outside Air Damper Supply Fan Air Flow Sensor Conditioned Space Heating Coil Cooling Coil Return Air Damper Relief Air Damper Return Fan Air Flow Sensor Return Fan Drive
Return Fan Outside Air Damper Heating Coil Return Air Damper Cooling Coil Supply Fan Inside Air Pressure Sensor Conditioned Space Relief Air Damper Return Fan Return Fan Drive Outside Air Pressure Sensor
Stairwell Pressurization Fan Pressure Sensor Fan Drive
Exhaust Fan Fan Pressure Sensor Fan Drive
Fume Hood Fan Fan Damper Positioning Motor & Limit Switch Fume Hood Fan Drive
Parking Garage & Tunnel Fan Vent. Fan Smoke Sensor CO Sensor Vent. Fan Drive
Primary CHW (HW, Water Source Heat Pump Circulating & Booster Pumps) Flow Sensor Flow Sensor Chiller Chiller Secondary Chilled Water Loop Primary Chilled Water Pumps Primary Chilled Water Pump Drives
Condenser Water Pumps Flow Sensors Cooling Tower Cells Chiller Chiller Condenser Water Pump Drives Condenser Water Pumps
Application Interfacing Operator s controls Plain language for Operation Fault display Programming Manual speed control Remote mounting Auto Application MACROs Hand/Off/Auto control OFF HAND
Single Motor Bypass Circuit Breaker, Bypass & Output contactors and fuses to service the drive while running Points to consider Can the system run at full speed? Drive fusing Safety interlocks Automatic bypass Run permissive circuit
Application Interfacing Operator s controls Bypass Single motor Multiple motor
PI and PID Controller (Closed Loop / Set Point) Compares the desired process variable with the set point value Proportional to the error Integral function adds errors over time Derivative function considers the rate of change of error (only for fast response systems) PID Speed Control Reference Set Point Feedback Sensor Controlled System
Other Considerations Environment Enclosure type NEMA 1 NEMA 12 Circulating dust Dripping non-corrosive liquid NEMA 3R Outdoor
Environment Other Considerations 1-50 HP: NEMA 1 & 12, & 3R Outdoors -15 to 50ºC (5 to 122ºF) No De-rate 60 HP - 550 HP: NEMA 1 & 12-15 to 40C (5 to 104F) Not exceed 10% de-rate @ 122F
Harmonics What? Non-linear loads draw non-sinusoidal current from a sinusoidal line (current doesn t look like voltage): Non-incandescent lighting Computer Equipment UPS (Uninterruptible Power Supplies) Telecommunications equipment Copy machines Variable Frequency Drives Electronic/Controls for Facility Elec. Equip. / Systems, Security, HVAC / Mech. equipment Any load with a solid state AC to DC power converter
Harmonics Why worry? Harmonic Voltage Distortion Increased heating in motors and other electromagnetic equipment Noisy operation of electromagnetic equipment Malfunctioning of sensitive electronics Nuisance tripping of electronic circuit breakers Overheating of PF correction capacitors Tripping of PF protection equipment Equipment downtime Premature component failures Failed motors and capacitors
Harmonics Why worry? Harmonic Current Distortion Added heating in transformers and cables, reduces available capacity May stimulate a resonance condition Excessive voltage Shutdown / damage to electronic equipment May cause telephone or electronic interference Failed transformers, equipment Not in Compliance with CODES, STANDARDS, REGULATIONS, IEEE, GOOD DESIGN PRACTICE
Include: Reactors (Chokes) Least expensive when specified to be included with base drive package 5% impedance AC line reactors -or- DC link reactors Both types provide similar harmonic benefits Also Suppress voltage transients that can cause equipment damage Harmonic Distortion Calculations = only VFD contribution
RFI / EMI RFI = RADIO FREQ. INTERFERENCE conducted through the air EMI = ELECTROMAGNETIC INTERFERENCE conduct through AC power line EFFECTS SIMILAR TO HARMONIC DISTORTION!
RFI / EMI Hardware RFI / EMI FILTERS: WILL BE INCLUDED IN ALL VFD SIZES ACH 550: Meets EMC PRODUCT STANDARD EN61800-3 FOR THE FIRST Environment restricted level BENEFIT: VFD will not interfere with other electronic equipment Other electronic equipment will not interfere with VFD
Serial Communications BAS / DDC Company Alignment BACnet ALC (Automated Logic Corp.) Andover Controls Novar American Auto-Matrix Alerton Trane Delta Controls Teletrol Tridium JCI (Johnson Controls, Inc.) Honeywell KMC LonWorks Honeywell Invensys Distech Novar TAC (formally CSI) JCI Trane Staefa Circon ModBus RTU ASI Controls KMC Reliable Controls