Power Supply ControlFeedback Control

Power Supply Control

Lesson ObjectivesWhen you finish this lesson you will understand:• Secondary Current Control• Phase Shift Heat Control• Spot Weld Quality Testing• Equipment Monitoring• Feedback Control

Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. View Demo5. Do on-line

workbook6. Do Homework

Keywords: Transformer, Tap Setting, Primary Current, Secondary Current, Silicon Controlled Rectifier, Electrode Force, Power Factor, Toroid, Hall Effect Transducer, Linear Voltage Differential Transformer, Dynamic Resistance

Block Diagram of Single-Phase Spot Welder

Spot Weld

Main Power Line

Contactor

Transformer Tap SwitchEs

Vp

Parallel/Series Tap SwitchesEs Es

EsEs

Vp

S1

S1

S2

S2

P2

P2

P1

P1Vp

(a) Parallel

(b) Series

N=np/ns

Vs= Vp/N

Is = Ip N

60 C

ycle

AC

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

Phase Shift Heat Control

(a) Current Controlled by Tape Settings

(b) Current Controlled by Phase Shift Setting

Link to:

Phase Shift Heat Control Demo

60 C

ycle

AC

Electrode

Electrode

Force Gage

Equipment ArrangementPowerSupply

Strain Gage Signal Conditioner

VoltageLeads

Tap

Displacement Transducer

IsolationBox

Integration

DataRecorder

Print

Oscilloscope