ABB Template

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Presented by Joe Eschleman VP Sales
Marketing Powerohm Resistors Inc.
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Outline
1. Principles of Dynamic Braking.
2. Regeneration and VF Drives.
3. Methods of braking.
4. Selecting / Sizing Braking Resistors
5. Selecting / Sizing Braking Modules
5. Tools (Powerohm VBR)
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Outline
1. Principles of Dynamic Braking.
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Principles of Dynamic Braking.

• To examine Dynamic Braking we first need to
  understand regeneration.
• Regeneration is the transfer of energy from the
  motors load back through the motor to the
  Variable Frequency Drive (VFD)
• Regeneration occurs when the rotor speed exceeds
  synchronous speed of the motor at the applied
  frequency
• This occurs during speed changes and with
  overhauling load applications. When speed and
  torque act in opposite directions.
• If regen is not properly dealt with, it can cause
  nuisance Bus Overvoltage trips in Variable
  Frequency Drives
• Regen is one of the most commonly overlooked
  application issue with Variable Frequency Drives.

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Sources of Regen Energy

• Kinetic Energy
• Rotational motion (based on inertia and velocity)
  
• Centrifuge
• Linear motion (based on mass and velocity)
• Conveyors
• Potential Energy
• Stationary energy (based on height and gravity)
• Hoist
• Overhauling Loads
• Continuous power driven from external sources
• Winding machines

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How to deal with Regen.

• Remember that regen occurs when speed control is
  required.
• You can use a mechanical brake.
• Disadvantage is a mechanical brake is a wearable
  part.
• Electrical Brake (DC Injection Brake, Flux
  Braking)
• Disadvantage is that the heat is dumped into the
  motor shortening the life expectance of the
  motor.
• Add a dynamic braking resistor
• Dynamic braking resistors dissipate the excess
  energy as heat.
• Use a line regen drive.
• Regen drives transfer the excess energy back on
  to the incoming AC line.

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When does Regen occur?Quadrants of Drive
Operation
Torque ()
Speed ()
Speed (-)
Torque (-)
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When does Regen occur?Quadrants of Drive
Operation
Torque ()
Speed ()
Speed (-)
Torque (-)
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Quadrant Summary

• Regeneration occurs when speed and torque act in
  opposite directions.
• Rotor speed exceeds synchronous speed of applied
  frequency
• Negative slip
• Load drives the motor and it becomes a generator
• Power (Torque x Speed)/5250
• When torque and speed oppose, power is negative
• Energy Power x time
• When power is negative, energy is negative

Negative energy Regenerative energy
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Outline
2. Regeneration and VF Drives.
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Regeneration and VF Drives

• Typical Diagram of an AC Drive?
• AC line power is converted to DC in the diode
  bridge section of the electronics.
• The DC bus section then smoothes and filters the
  waveform.
• The inverter section inverts the DC voltage back
  to AC..
• The IGBTs of the inverter section are turned on
  and off varying the AC voltage and frequency
  output, thus controlling the speed of the motor.

DC Bus
Diode Bridge
Inverter
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Regeneration and VF Drives

• What happens to an AC Drive during regeneration?
• Motor acts as generator (rotor turns faster than
  synchronous speed of applied Hz)
• AC from the motor is rectified by the IGBTs
  diodes.
• Input diode or SCR bridge cannot conduct back to
  the line supply.
• Energy charges the DC bus capacitors, causing the
  DC bus voltage to rise.
• The drive trips on Bus Overvoltage

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Outline
3. Methods of braking.
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Braking Methods

• Factors affecting the choice of braking method.
• Amount of braking (force) needed
• Amount of control needed
• Consistent, responsive stop time
• Consistent stop position
• Continuous vs. intermittent operation duty
  cycle
• Braking vs. overhauling
• Relative cost To Purchase and To Maintain
• E-Stop categories
• If heatwhere is it dissipated?

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Braking Methods - Mechanical

• Mechanical Braking
• Advantages
• Simple, no electronics
• Failsafe, provides braking when power is removed
  or drive trips.
• Disadvantages
• Costly, high maintenance
• Energy lost as heat
• Deceleration is not controlled (time, position)

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Braking Methods - Electrical

• DC Injection Braking
• DC current is injected into the motor, forcing it
  to zero speed
• Advantages
• Built into most drives, no additional hardware or
  cost
• Disadvantages
• Stop is not controlled
• Energy dissipated as heat in the motor

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Braking Methods - Electrical

• Flux Braking
• Motor flux current is increased
• Advantages
• Built into most drives, no additional hardware or
  cost
• The braking is controlled.
• Disadvantages
• Stop is not controlled (non-linear)
• Most effective at half speed and below
• Energy dissipated as heat in the motor
• Not regenerative
• Useful for deceleration only
• Not for overhauling

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Braking Methods - Electrical

• Bus Regulation
• As drive decelerates and bus voltage rises, the
  drive automatically extends the ramp to prevent
  excessive bus voltage and drive trip.
• Advantages
• No additional hardware required.
• Disadvantages
• Not a true braking technique it merely
  mitigates overvoltage trips.

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Braking Methods - Electrical

• Braking Chopper and Braking Resistor
• Chopper control circuitry monitors the DC bus
  voltage
• If regeneration causes the bus voltage to rise
  above a certain level, the chopper turns on and
  shunts the energy through a DB resistor

? Dynamic Brake or Chopper
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Braking Methods - Electrical

• Dynamic Braking
• Advantages
• Simple, low cost
• Controlled braking
• Removes energy from drive and dissipates heat in
  power resistor specifically designed for the task
• Suitable for decelerating and overhauling loads
• Disadvantages
• Energy is lost to heat
• Overheating can be a concern
• Environment

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Braking Methods - Electrical
Braking vs. Overhauling?

• Braking
• Braking is defined as an application in which you
  are decelerating the speed of drive.
• This could be changing speeds or in the extreme
  case, an E-stop application.
• Overhauling
• Overhauling is defined as an application in which
  the motor is being driven by the load on the
  motor, (external forces).
• A Hoist lowering or tensioning machines.

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Braking Cycle Curve
Energy Dissipated During Fixed Torque Stop
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Overhauling Curve
Energy Dissipated During Overhauling
1 pu
t0
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Braking Methods - Regeneration

• Line Regeneration
• Energy is returned to the line supply via an
  external regen module or via an VFD with an
  active converter.
• Advantages
• Controlled braking
• Energy is recycled to the line supply
• Can provide improved power quality
• No limitations in duty cycle, suitable for higher
  HPs
• Disadvantages
• Relatively costly
• More complex electronics, more parts
• Not possible when power source is a generator.

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Braking Methods - Regeneration
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Application Examples

• DC Injection Braking, Flux Braking
• Applications with intermittent fast stops where
  no precision or consistency is required
• Conveyors
• Bus Regulation
• Applications where tripless operation is required
  but stop time is not critical
• Conveyors, High Inertia Fans
• Applications where intermittent overhauling duty
  may occur and speed accuracy is not critical
• Pump Jacks

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Application Examples

• Dynamic Braking
• Loads requiring quick response for deceleration
  or stopping
• Conveyors
• Chipping Heads
• Centrifuges
• Intermittent overhauling loads
• Rotary Kilns
• Punch Press
• Pump Jacks
• Medium HPs and duty cycles

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Application Examples

• Line Regeneration
• Frequent overhauling loads
• Unwinds
• Hoists
• Rail Car Dumpers
• Centrifuges (batch process)
• Higher HPs and duty cycles

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Outline
4. Selecting / Sizing Braking Resistors
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DB Resistor Sizing

• Methods of sizing resistor
• Refer to operation manual or pricing guide.
• General method (Ohms and Watts) Supplied by
  AB Calculator
• Drive specific (HP, Volts, Torque Rating, Duty
  Cycle)
• OEM Specific (HP, Volts, IGBT Rating, Duty Cycle)
• Application Driven Calculation
• Powerohm VBR (Variable Braking Resistor
  /Analyzer)

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DB Resistor Sizing

• General method (Ohms and Watts)
• Many customers use their own calculations or
  calculations established by specific drive OEMs
  to come up with an ohms and watts. In this case
  Powerohm designs a resistor using standard
  components to meet the requirement assuming the
  watts is a continuous rating.

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DB Resistor Sizing

• Drive specific (HP, Volts, Torque Rating, Duty
  cycle)
• When given the above information Powerohm uses an
  equation to calculate the continuous watts and
  ohms of the resistor necessary for the given
  requirements.
• Watts HP 746 Torque Duty Cycle Duty
  Cycle sizing factor
• Ohms (dcV ) 2 .
• HP 746 Torque
• Resistance calculated above must be sized to
  meet the minimum resistance value supplied by
  drive OEM.

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DB Resistor Sizing

• OEM Specific (HP, Volts, IGBT Rating, Duty Cycle)
• Working directly with the drive OEM, resistors
  are sized on the limitations of the brake module
  or 7th IGBT
• Based on the limitations of the IGBT a maximum
  available braking torque can be calculated.
• Watts HP 746 Torque Duty Cycle Duty
  Cycle sizing factor
• Torque rating is minimum of torque required for
  the application vs max torque rating of IGBT
• Minimum Ohms (dcV) ___ .
• IGBT current limit

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DB Resistor Sizing

• 7th IGBT vs External brake chopper
• The 7th IGBT may be a limiting factor for the
  braking torque available to a drive. In this
  case a separate brake chopper can be purchased to
  be connected to the drive instead of using the
  7th IGBT.
• Watts HP 746 Torque Duty Cycle Duty
  Cycle sizing factor
• Torque rating is minimum of torque required for
  the application vs max torque rating of the motor
• Minimum Ohms (dcV) .
• Brake chopper current limit
• Resistance calculated above must be approved to
  meet minimum resistance value supplied by drive
  OEM.

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DB Resistor Sizing

• Duty cycle calculations
• The duty cycle is determined based on the on time
  versus total of a braking cycle, with the total
  braking cycle not to exceed 2 minutes.
• Depending upon the duty cycle different watts
  multipliers are used to determine the correct
  continuous rating of the resistor. Higher duty
  cycles require lower multipliers, this is to
  account for the high peak currents of the lower
  duty cycles.

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AB Calculator (Jeff Theisen)
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AB Calculator (Jeff Theisen)
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AB Calculator (Jeff Theisen)Any Resistor
Selected from Drop Down Menu
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AB Calculator (Jeff Theisen)Power Resistor
Selected from Drop Down Menu
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AB Calculator (Jeff Theisen)Finite Resistor
Pick List
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1336 Brake Chopper and Resistor Table
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1336 Brake Chopper and Resistor Table
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Raise SoftwareProduct Configurator
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Raise SoftwareProposal Works
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Outline
5. Selecting / Sizing Braking Modules
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Overview

• Ratings, Technical Data, Monitored Conditions and
  Protection
• Frame Sizes, Weights and Dimensions
• Part Numbers
• Operation and Maintenance Manual
• Brochure and Release Dates

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Ratings

• Continuous Amps
• 50, 115, 300, 600, 900 and 1200 amp
• (Units above 50 amp include fan)
• Voltage Ratings
• 240, 480, 600 volts (690 for 300 amps and
  above)
• Ambient Temperature
• -10 to 40 Deg C
• Logic Power Supply
• Derived from DC Bus _at_ 40 Watts Nominal
• Derived from 115 VAC for 300 amps and above
• Fan Supply
• Single Phase 115 VAC

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Input / Output Low Capacity 50 and 115 amp units

• Enable
• Internal/External Jumper Programmable
• Enable is 115 VAC, also provides fan power if
  equipped.
• Master Output
• Slave Input
• Fault Contacts
• Jumper Programmable NO or NC (factory default is
  NC)

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Monitored Conditions Low Capacity 50 and 115
amp units

• Shorted IGBT Transistor
• Open or Absent Resistor Load Bank
• Logic Supply Undervoltage
• Heatsink Over Temperature Shutdown

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Input High Capacity 300 through 1200 amp units

• Power
• Derived from single phase AC voltage.
• I/O
• All high capacity modules have additional
  standard I/O features compared to lower capacity
  modules. Higher current ratings generally are or
  may be associated with more complex drive
  systems.
• Enable
• Close Contact to enable

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Input Continued High Capacity 300 through
1200 amp units

• Master / Slave Signal
• Pulse train, Bi-directional signal, two terminal
• IOC, (Instantaneous Over Current)
• Reset Momentary contact closure
• IOV, IUV (Instantaneous Over/Under Voltage)
• Reset Momentary contact closure
• Master/Slave Select
• Default Slave, Contact Closure Master
  Selected
• DC Bus Discharge
• Close Contact to discharge

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Output High Capacity 300 through 1200 amp units

• Logic Section Ready Normally Closed
• Power Section Ready Normally Closed
• Master / Slave Status Closed when Master
• IOC, IOV Normally Closed
• IOV, IUV Normally Closed
• Over temperature Normally Closed
• Logic Voltage Valid Normally Closed
• IGBT Shorted Normally Closed

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Protection High Capacity 300 through 1200 amp
units

• Logic Supply Undervoltage Shutdown / Lockout
• IOC Shutdown
• IOC, IOV Shutdown
• Heatsink Over Temperature Shutdown

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Options High Capacity 300 through 1200 amp units

• Profibus I/O Module.
• Standard hardware I/O remains active.
• Fiber optic link for Master pulse transmission
  between modules.
  Recommended in
  high noise environments when multiple modules are
  used.

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Powerohm Type BM Low Capacity Braking Module
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Powerohm Type BM High Capacity Braking Module
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IMPORTANT These instructions should be read
thoroughly before installation. All warnings and
precautions should be observed for both personal
safety and for proper equipment performance and
longevity. Failure to follow these instructions
could result in equipment failure and/or serious
injury to personnel.
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Outline
5. Tools (Powerohm VBR)
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Powerohm VBR

• Powerohm Variable Braking Resistor
• The Powerohm VBR is a portable test unit that
  provides selectable steps of resistance for
  analyzing your braking requirements for a wide
  range of drive horse powers. Simply connect the
  VBR to your drive or braking module and let the
  application decide what braking resistor it needs.

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Powerohm VBR

• Powerohm Variable Braking Resistor
• This easy to use diagnostic tool provides the
  user with eleven (11) selectable settings of
  resistance.

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Powerohm VBR

• Powerohm Variable Braking Resistor
• After selecting the resistance value suitable for
  your drive, connect the plus (red) and minus
  (black) leads to the output of the Brake Chopper
  section (imbedded within the Drive or stand alone
  external). Now run your application for a
  minimum of 30 minutes.

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Powerohm VBR

• Powerohm Variable Braking Resistor
• After running your application for 30 minutes you
  will notice the digital readout has changed to
  higher value.
• Pressing the up arrow key will provide you with
  the peak readout during your cycle.
• Together with this peak number and the resistance
  value you selected you are now ready to determine
  the ideal resistor for your application.

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Powerohm VBR

• Powerohm Variable Braking Resistor

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Powerohm Resistors, Inc.Engineered Diversity for
the Braking Resistor Industry
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Summary

• Questions?