Variable Frequency Drive Training Online
Instructor
Paul Wright, Motors and Drives Consultant, The Electricity Forum
DAY ONE
1. Typical Distribution System Overview
This seminar will discuss the Distribution components that make up a typical system and how they relate and impact the VFD and Motor selection.
- Point of Common Coupling
- Fault Capacity
- Transformers
- Capacitors
- Switchgear
- Low Voltage MCCs
- VFDs
- Motors
- Other Loads
- Reactors, Sine Filters and DVDT filters
Benefits of Using Variable Frequency Drives: The many benefits of using Variable Speed Drives will be discussed for several different applications such as fans, pumps conveyors and process machines.Lifting and hoistion application and we will describe the differences in hardware and application requirements for these. Several common reasons for using VFDs from Energy Savings, Unlimited Starting and Reversing, Precise Process control, Extension of Equipment Life will be reviewed. Significant capital and operating costs reduction possibilities will be shown.
2. Understanding AC Motors
This presentation will provide discussion on motor theory as applied to fixed speed and variable speed operation. The presentation will discuss the different motors’ performance and features available to the user: This presentation will start at the generation of a magnetic field and how to control this field to provide useful work. The following characteristics will be individually discussed to show their impact on the overall performance of the motor. Some of these characteristics will differ with changes in line voltages, line frequencies or both.
- Power Factor
- Rated RPM (synchronous RPM)
- Rated Voltage
- Rated Frequency
- Rated Current
- Equivalent Circuit Parameters
- Slip
- Starting, Pull-up and Breakdown Torques
- Service Factor
- Design Frames
- Insulation Ratings
- Temperature rise design
We will demonstrate the use of diagnostic parameters on most fof todays VFDs providing valuable information on VFD thermal, and Calculated/real motor thermal states.
3. Understanding VFDs
This presentation will discuss the topology of todays’ low voltage VFDs. The function of the Rectifier, Pre Charge Circuit, DC Bus Capacitors, Chopper Circuit and Inverter section will be discussed. Discuss when to select PWM Control (V/Hz) or Vector Control operating modes. Discuss the selection of the voltage and current ratings of the VFD and the individual components that make up the complete system to show how the reliability of the VFD is improved. We will show the Low harmonic and Active front end VFD options and describe the functionality and effect of the AFE on the VFD sysetm.
- VFD Overview
- Enclosures Types
- Voltage rating and Tolerance
- Current Capacity and Overload Capability
- VFD System Components
- Disconnect Switch or Circuit Breaker
- Line Filtering
- Surge Protection
- Fused Control Power
- 120Vac and 24VDC control
- Isolating Contactor
- Bypass Control Schemes
- Motor Filters
- Analog isolators
- Enclosure Heating and Cooling Requirements
- Dedicated Customer Field Connection Terminal Blocks
- Motor control performance comparison on Fixed Speed and Reduced Voltage Starting will be compared to VFD Operation.
- Starting
- Stopping
- Braking
- Reversing
- Over and Under nominal Line Voltage
This presentation will also provide a short digital tour a motor plant to show the different manufacturing steps to the assembly of an Above NEMA Squirrel cage Motor.
Daily Summary and Seminar wrap up
DAY TWO
4. Motor Performance
The operation performance of AC Motors on fixed speed starters, reduced voltage solid state starters and on VFDs will be reviewed. This presentation will outline the significant differences in overall performance that the motor produces while starting, stopping, braking and reversing direction for the different control methods. Several new torque and current speed motor curves will be presented to highlight changes and their effect into the distribution system. Discussion of welding of contacts in motor starters and fuse failure or Circuit Breaker tripping when starting high inrush motors.
The torque and current versus speed curve characteristics will be discussed.
- Torque Characteristics
- Locked Rotor Torque (LRT)
- Pull-up Torque (PUT)
- Breakdown Torque (BDT)
- Full Load Torque
- Current Characteristics
- Locked Rotor amperes (LRA)
- Peak Asymmetrical Current
- Full Load current
5. NEMA Motor specification Part 30 and Part 31 differences
This presentation will discuss the differences between the Standard for Part 30 designed Motors and the Standard for Part 31 designed Motors.
- Nameplate Information
- Cooling methods
- Stator wiring
- Speed Range
- dv/dt and Voltage Stress design
We will also review the motor technical ratings for typical NEMA motors built to NEMA Part 30 and 31 designs including: HP, RPM, FL RPM, NL AMPS, FL EFF., FL TORQUE and the equivalent circuit impedances. Understanding how the Voltage and Frequency affect Motor Performance: We will show the relationship of changing of the voltage and frequency will impact the development of torque and the speed of the motor. We will also discuss the differences in the Torque/Current versus Speed curve for motor on a fixed speed application versus that for a VFD operation. Encoder Speed/Torque Feedback and Analog Feedback should be discussed when applied with different motor control methods.
Temperature, Service Factor & Insulation Class: The above electrical design criteria is necessary to ensure the motor can provide a suitable operating life in a given application. Each of the above criteria can have significant detrimental impact on the motors’ life. An increase of 10 degree Celsius temperature rise in the motor will cause a 50% reduction in the motors’ insulation life. We will focus on Industry standard differences, such as ratings and
nameplate difference from Nema to IEC derived product etc.
6. Understanding VFDs
This presentation will discuss the topology of todays’ low voltage VFDs used with PWM or Vector Control schemes. The function of the Rectifier, Pre Charge Circuit, DC Bus Capacitors, Chopper Circuit and Inverter section will be discussed. Discuss when to select PWM Control (V/Hz) or Vector Control operating modes. Discuss the selection of the voltage and current ratings of the VFD and the individual components that make up the complete system to show how the reliability of the VFD is improved. The student will learn how to select the VFD models from various Manufacturers that will be more reliable and have longer Mean Time Between Failures (MTBF).
- VFD Overview
- Enclosures Types
- Voltage rating and Tolerance
- Current Capacity and Overload Capability
- VFD System Components
- Disconnect Switch or Circuit Breaker
- Line Filtering
- Surge Protection
- Fused Control Power
- 120Vac and 24VDC control
- Isolating Contactor
- Bypass Control Schemes
- Motor Filters
- Analog isolators
- Enclosure Heating and Cooling Requirements
- Dedicated Customer Field Connection Terminal Blocks
7. Power Quality and Up Stream Issues
This presentation will look at the line side issues that a VFD may have on the power system. All the following issues will be discussed along with the recommended solution(s) for each issue:
- Fault Capacity
- Harmonic Limitations (Voltage and Current Distortion)
- Power Quality
- Power Factor
- Voltage and Tolerance
- Transients and Surges
- Short term and Long term Power Loss
We will demonstrate a real measured harmonic effect clipping and distortion with the use of Scope and waveforms and how it relates to drawn current. We wil demonstrate how the effects on the screen for students to see.
8. Motor and Cable Down-Stream Issues
This presentation will look at the load side issues that a VFD may have in the motor circuit. All the following issues will be discussed along with the recommended solution(s) for each issue:
Bearing Currents:
The effect of current flowing through the bearings and bearing housing will cause the inner and outer raceways to pit. Over time the pitting will continue to increase the depth of the groves and the bearing will eventually be damaged. The causes and remedies for bearing current issues will be discussed.
VFD Cables:
Why shielded VFD cables are recommended by the VFD manufacturers. We will also describe the limitations of the shielded cabling in certain scenarios such as high PWM carrier frequency.
Radio Frequency and Electro Magnetic interference:
How they are produced and steps to mitigate the transmission of these unwanted noise signals. These high frequencies exhibit special characteristics that may cause undesirable effects in the industrial distribution and communication systems. Effects of EMC filtering on the High impedance grounded or HRG grounded systems. Limitations of the VFD EMC filtering when used in non-solidly grounded power systems, will also be covered.
VFD and Motor Selection Examples:
This part of the presentation will look at a few applications where the operating performance characteristics for continuous and intermittent speed and torque ranges are provided. The student will be able to select the best combination of motor and VFD based on meeting or exceeding the specified criteria. The student will see the cost impact of their selection for the Motor and VFD to the cost of other possible acceptable selections.
Programming and Testing:
The most common 50-70 VFD setting parameters will presented. We will provide a parameter list for several different VFD manufacturers. The testing of the VFD packaged system is a very important procedure that makes the whole System complete. This verifies the controls and power wiring function as specified. A good testing program enables the VFD to be installed and commissioned on site without any issues. The proposed testing and commissioning procedures will be discussed.
- Routine Testing
- Certified Full Load Testing
- Heat Run Testing in 40oC ambient
Review of VFD Specification:
A generic non manufacturer biased VFD specification is provided to specify the minimum systems components to provide a for a reliable VFD package.
Daily Summary and Seminar wrap up
All students attending this presentation will receive electronic copy of the 9 Presentations plus several papers and booklets discussing the course and related material. A detailed VFD specification and Data Sheets will also be included to ensure future drive purchases provide reliable trouble free installations.
CLOSED LOOP and PID apllications
Students will be introduced to Closed loop application and hardware requirements. We will introduce students to PID application provided by many wendors and what is needed to implement and show advantages of such installations.
Students will learn the vendor Specific commissioning software functionality, limitations and cost comparison. We will discuss network connectivity and parameters that are to be used of diagnostic maintenance and life expectancy monitoring. We will apply a real Oscilloscope and probe system on the Demo VFD unit showing the effects of NO reactor With reactor, Long and Short cables and transient (Reflected) noise on the motor side. The instructor will also demonstrate the real temperature rise of the loaded VFD, show the troubleshooting and maintenace testing and basic static check testing in event of a VFD failure Maintenance procedures, intervals and consumables should be discussed.
COURSE TIMETABLE
Both days:
Start: 8:00 a.m.
Coffee Break: 10:00 a.m.
Lunch: 12:00 noon
Restart: 1:15 p.m.
Finish: 4:30 p.m.
