Power Systems - PowerPoint PPT Presentation

Loading...

PPT – Power Systems PowerPoint presentation | free to download - id: 3e1486-OGE0M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Power Systems

Description:

Power Systems Machines and Equipment Cooling System Mechanical System Force generation system Pneumatic/Hydraulic system Motor or foot-operated system Electrode ... – PowerPoint PPT presentation

Number of Views:64
Avg rating:3.0/5.0
Slides: 53
Provided by: ddick6
Category:
Tags: power | system | systems

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Power Systems


1
Power Systems
2
Power Systems
  • Learning Activities
  • View Slides
  • Read Notes,
  • Listen to lecture
  • Do on-line workbook
  • Do Homework
  • Lesson Objectives
  • When you finish this lesson you will understand
  • Control of the high electrical power systems,
    transformer control
  • Timing functions
  • Calculation of the heat
  • Troubleshooting

Keywords Power Systems, Single Phase AC, Single
Phase Rectified, Three Phase, Three Phase
Rectified, Frequency Changer, Inverter,
Transformer, Tap Switches, Saturation,
Hysteresis, Reactance, Inductance, Resistance,
Impedance, Power Factor, Duty Cycle, Timing
Controls, Synchronous, Phase Shift Heat Control,
SCR, half wave rectified, Full Wave Rectified
3
Machines and Equipment
  • Cooling System
  • Mechanical System
  • Force generation system
  • Pneumatic/Hydraulic system
  • Motor or foot-operated system
  • Electrode application system
  • Rocker arm or pinch type
  • Press or direct action type
  • Portable system
  • Electrical System
  • Single-phase system
  • Single-phase rectified system
  • Three-phase rectified system
  • Frequency changer system
  • Frequency inverter system

4
Block Diagram of Single-Phase Spot Welder
Contactor
Main Power Line
Spot Weld
5
Configurations for Spot Welding Transformers
(a) Stacked, Shell Type (b) Stacked, Core
Type (c) Wound Type
6
W. Stanley, Resistance Welding McGraw-Hill, 1950
7
(No Transcript)
8
Parallel/Series Tap Switches
Es
Es
(a) Parallel (b) Series
S2
S1
Vp
P2
P1
Es
Es
S2
S1
Vp
P2
P1
9
Transformer Tap Switch
Es
Vp
10
Induced Magnetic Filed
Saturation Induction
Remnant Induction
Coersive Force
Applied Magnetic Field
Structure Properties of Materials, Wiley, 1967
11
X reactance in Ohm L inductance in Henry f
frequency in Hertz Z impedance in Ohm R
resistance in Ohm
Rp
Xs
Rs
Xp
12
Power Factor
AC Current
DC Current
Ohms Law
  • Z Impedance
  • X Reactance
  • Frequency of AC
  • Geometry of Secondary
  • Magnetic Material

I Current V Voltage R Resistance
Power VI KW (kilowatts)
Power KVA
13
Power Factor
P
P
V
I
V
I
(a) Purely Resistive Load (b) Resistive
and Reactive Load
Pav VavIav cos(f)
14
Power Factor Cos
If I10,000 amps V10 volts
Kva100 Kw70.7
If RX pf 70.7
15
Variables Affecting Power Factor
  • Machine Design
  • Single-Phase versus Three-Phase Current
  • Frequency
  • Reactance/Resistance of the Secondary Loop
  • Magnetic Material in the Throat

16
Increased Throat Length
X
R
Increased Angle Decreased Power Factor
Resistance Welding Manual, RWMA, 1972
17
Ferrous Material in Throat
X
R
Reduced Power Factor
Resistance Welding Manual, RWMA, 1972
18
Power Factor Correction Capacitors
Contactors (Switched Simultaneously)
AC Power Supply
High Impedance DC Charging Circuit
(a) Shunt Capacitors (b) Series Capacitors
Normally-Closed Contactor
Welding Contactor
Discharging Resistor
AC Power Supply
Tuned Capacitor
19
Duty Cycle is the power level at which a
transformer can operate for some fraction of time
without overheating
Percent Rated Load
100
50
Percent Duty Cycle
20
Timing Controls
At what point in time do we close the contactor
  • Non-synchronous Controls
  • Synchronous Controls
  • Microprocessor Control Synchronous

21
Synchronous Timing Accuracy
Electronic Control Res. Weld, McGraw-Hill, 1943
22
Transient Currents with Non-Synchronous Timing
Electronic Control Res. Weld, McGraw-Hill, 1943
23
Electronic Control Res. Weld, McGraw-Hill, 1943
24
  • Control of Secondary Current
  • Transformer Tap Setting (Turns Ratio)
  • Phase Shift Heat Control

25
Gate
Cathode
Anode
  • Rules for SCR Conduction
  • can conduct when anode is with respect to
    cathode
  • once initiated, can only be stopped by removal
    of anode voltage
  • initiated by a pulse on ignitor

26
Welding Handbook
27
Idealized Phase Shift Heat Control
(a) Current Controlled by Tape Settings (b)
Current Controlled by Phase Shift Setting
In Actual Case, Current can not instantaneously
change
28
Actual Condition
Firing Angle
Hangover Angle Related to R/L ratio
Androvich Resistance Welding Constant Current
Heat Control, AWS Sheet Metal ConfV, 1992
29
IRN Normalized Available RMS Current
Androvich Resistance Welding Constant Current
Heat Control, AWS Sheet Metal ConfV, 1992
30
Tsai, Experimental Study of Weld Nugget Expan,
Paper B1, Sheet Metal Welding Conf V, AWS, 1992
31
(No Transcript)
32
Link to Phase Shift Heat Control Demo
33
Portable Trans Guns
Transformer Integral with Gun Thus smaller in Size
Nedorezov, J Using Portable Transguns for
Resistance Spot Welding, Practical Welding
Today, Nov-Dec 1997
34
Nedorezov, J Using Portable Transguns for
Resistance Spot Welding, Practical Welding
Today, Nov-Dec 1997
35
Machines and Equipment
  • Cooling System
  • Mechanical System
  • Force generation system
  • Pneumatic/Hydraulic system
  • Motor or foot-operated system
  • Electrode application system
  • Rocker arm or pinch type
  • Press or direct action type
  • Portable system
  • Electrical System
  • Single-phase system
  • Single-phase rectified system
  • Three-phase rectified system
  • Frequency changer system
  • Frequency inverter system

36
Single-Phase Rectified System
Center-Tapped Transformer
Bridge-Type Rectifier
Primary Current Secondary Current
37
Single-Phase Rectified System
  • Advantages
  • Higher Power Factor
  • More Uniform Heat Flow Pattern
  • Less pf Loss by Material in Throat
  • Disadvantages
  • Expensive
  • Need Heavy Duty Diodes
  • One Electrode Wears Rapidly
  • Load on one side of Three Phase Line
  • Balanced 3 phase hook-up needed

A
B
C
38
Machines and Equipment
  • Cooling System
  • Mechanical System
  • Force generation system
  • Pneumatic/Hydraulic system
  • Motor or foot-operated system
  • Electrode application system
  • Rocker arm or pinch type
  • Press or direct action type
  • Portable system
  • Electrical System
  • Single-phase system
  • Single-phase rectified system
  • Three-phase rectified system
  • Frequency changer system
  • Frequency inverter system

39
Three-Phase Rectified System
Half Wave
Full Wave
Primary Current
Primary Current
100 Heat
Secondary Current
10 Heat
Secondary Current
40




120
Half Wave
120
Full Wave
120
41
Spinella, D., Al RSW Capital and Operating
Costs, AWS Xsheet Metal Conf, 1996
42
Comparison of Two PF on Three Machines
High Ripple
Roth, Alternating Current Vs DC in Resistance
Welding AWS Sheet Metal Conf IV, 1990
Medium Ripple
Low Ripple
43
Comparison of Two PF on Three Machines
  • Both Single Phase and 3 Phase DC is best in low
    power factor (high inductive) circuits providing
    as much smoothing as possible
  • Phase shifting will increase ripple (more in
    single phase). Operate on the highest phase
    shift and lowest tap setting possible

44
Need to get comparison with 3 phase DC circuit 2
as 100
Roth, Alternating Current Vs DC in Resistance
Welding AWS Sheet Metal Conf IV, 1990
45
  • Disadvantages
  • Expensive
  • Need Heavy Duty Diodes
  • One Electrode Wears
  • Advantages
  • High Power Factor
  • Uniform Heat Flow
  • No need to balance hook-up
  • No pf loss by material in throat

46
Machines and Equipment
  • Cooling System
  • Mechanical System
  • Force generation system
  • Pneumatic/Hydraulic system
  • Motor or foot-operated system
  • Electrode application system
  • Rocker arm or pinch type
  • Press or direct action type
  • Portable system
  • Electrical System
  • Single-phase system
  • Single-phase rectified system
  • Three-phase rectified system
  • Frequency changer system
  • Frequency inverter system

47
Frequency Converter
1
Controller A
2
Controller B
3
Controller C
48
Frequency Changer System
(a) Frequency-Changer (b) Rectified
49
  • Advantages
  • Power Factor gt 98
  • Balanced Loading
  • Balanced Electrode Wear
  • Disadvantages
  • Cost
  • Control Problems

50
Machines and Equipment
  • Cooling System
  • Mechanical System
  • Force generation system
  • Pneumatic/Hydraulic system
  • Motor or foot-operated system
  • Electrode application system
  • Rocker arm or pinch type
  • Press or direct action type
  • Portable system
  • Electrical System
  • Single-phase system
  • Single-phase rectified system
  • Three-phase rectified system
  • Frequency changer system
  • Frequency inverter system

51
Frequency Inverter System
Oscillator
Rectifier
AC HF
DC
AC 60 Hz
400, 600, or 1200 Hz
52
Advantages
Disadvantages
  • Cost
  • Newer Process Still Under Development
  • High Power Factor gt 98
  • Less Core Material
  • Lighter Smaller suitable for robots

53
Homework
Duty Cycle
About PowerShow.com