Adjustable Frequency Drive HVAC Application Fundamentals

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Adjustable FrequencyDrive HVAC Application
Fundamentals
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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

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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

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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

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Why Adjustable Speed?

• Energy savings
• System control
• Reduced maintenance
• Sound control

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Why Adjustable Frequency Drives?

• Minimum maintenance
• High efficiency
• Easy retrofit
• Remote mounting
• Simple control
• Bypass capability

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Cooling Tower Fluid Cooler Fan
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VAV AHU Supply Fan
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Secondary CHW (HW) Pump
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Smoke Extraction
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CAV Fan Clean Rooms
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Return Fan
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Return Fan
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Stairwell Pressurization
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Exhaust Fan
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Fume Hood Fan
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Parking Garage Tunnel Fan
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Primary CHW (HW, Water Source Heat Pump
Circulating Booster Pumps)
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Condenser Water Pumps
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Application Interfacing

• Operators controls
• Plain language for
• Operation
• Fault display
• Programming
• Manual speed control
• Remote mounting
• Application MACROs
• Hand/Off/Auto control

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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

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Application Interfacing

• Operators controls
• Bypass
• Single motor
• Multiple motor

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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)

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Other Considerations

• Environment
• Enclosure type
• NEMA 1
• NEMA 12
• Circulating dust
• Dripping non-corrosive liquid
• NEMA 3R
• Outdoor

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Other Considerations

• Environment
• 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 40?C (5 to 104?F)
• Not exceed 10 de-rate _at_ 122?F

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Harmonics What?

• Non-linear loads draw non-sinusoidal current from
  a sinusoidal line (current doesnt 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

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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

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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

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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

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RFI / EMI
RFI RADIO FREQ. INTERFERENCE conducted through
the air
EMI ELECTROMAGNETIC INTERFERENCE conduct
through AC power line
EFFECTS SIMILAR TO HARMONIC DISTORTION !
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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

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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