Embed Size (px)
Citation preview
Ref: P .ppt (19/04/23) 1EUROTHERM CONTROLS
THYRISTORSTHYRISTORS
WHAT ARE WHAT ARE THYRISTORS ?THYRISTORS ?
Ref: P .ppt (19/04/23) 2EUROTHERM CONTROLS
THYRISTORSTHYRISTORS 1. What is a thyristor unit?
2. What do they do?
3. Why use them?
4. Why tell us about them?
5. What questions should I ask?
Ref: P .ppt (19/04/23) 3EUROTHERM CONTROLS
WHAT IS A THYRISTOR UNITWHAT IS A THYRISTOR UNIT It is a switch - It is either ON or it is OFF.
It consists of solid state power switching devices, controlled by an input signal from a controller, computer etc.
It can be driven by LOGIC or ANALOGUE input signals or by Profibus / Modbus comms.
Models are available for single or three phase loads.
Ref: P .ppt (19/04/23) 4EUROTHERM CONTROLS
WHAT DO THEY DO ?WHAT DO THEY DO ?
1. They control the power delivered to electric heaters. Current ratings range from 1 to over 2,000 amps.
2. The load can be a simple resistance, one which changes resistance with temperature or a transformer coupled load.
3. Various firing techniques are available to suit the different applications.
Ref: P .ppt (19/04/23) 5EUROTHERM CONTROLS
WHY USE A THYRISTOR ?WHY USE A THYRISTOR ?
1. Unlike mechanical contactors, they are virtually maintenance free.
2. Contactors have slow cycle times which can cause heater fatigue due to hot / cold
stress.
3. Thyristors can provide soft start and current limit, thus reducing the current rating of associated cables, circuit breakers etc.
Ref: P .ppt (19/04/23) 6EUROTHERM CONTROLS
SO WHY TELL SO WHY TELL USUS ABOUT ABOUT THEM ?THEM ?
1. The most common outputs from EPA systems are 4-20 mA or digital comms. These can be used to control up to 2.5MW of power via a thyristor unit.
2. Model 394 chart recorders can have 4-20 mA control outputs which can be similarly used.
3. There could well be other temperature control loops within a system which
could use thyristors - and help the sale.
Ref: P .ppt (19/04/23) 7EUROTHERM CONTROLS
WHAT QUESTIONS SHOULD I ASK ?WHAT QUESTIONS SHOULD I ASK ?
1. Are there any heating applications in addition to the process loops ?
2. If so are they electric heaters ?
3. If so are they resistive, high temperature coefficient (HTCL) or transformer coupled loads ? This determines the firing mode.
