Download Thyristors Power Control

Why Thyristor Power Control Units Rather Than
Contactors?

Better Temperature Control
power demand
-
Deliver short bursts to match
-

Eliminates Temperature Fluctuations

Increased Production

Lower Maintenance Costs - no moving parts and plug in

Process Protection - Current and Power limits protects

Lower Energy Costs - Allows plant wide energy monitoring
Sense changes in
supply and adjust power delivery to prevent power fluctuations
-
built in diagnostics and partial load
failure detection allow preventative maintenance before total
failure and costly shut downs of process
design increases heating element Lifetime - reduced thermomechanical stress
process and heating elements
which reduces peak demand
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Thyristor Power Control
Thyristor Device
Will only conduct one way
Gate
Anode
EUROTHERM
CONTROLS
Cathode
Ref: P
.ppt (14/05/2017) 2
Parallel Pairs
Firing
Circuit
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Protection
Snubber - Resistor/ Capacitor for elimination of spikes and false
triggering particularly on transformer loads.
MOV - Metal Oxide Varistor - Resistance changes on voltage, as voltage rises
mainly on spikes it will absorb the excess voltage
Fuse - Protecting against over current draw, will blow faster than the
thyristor operates.
Control
Circuit
Firing
Circuit
Isolation
Eurotherm
Thyristor
Unit
Fuse
Snubber
MOV
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Firing Modes




Logic
Burst / Whole Cycle
Single Cycle
Phase Angle
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Logic Firing - Logic Input

On at Voltage zero.

Off at Current zero.
To minimise interference the thyristor unit switches
on at the first zero crossing of the mains voltage after
the the logic input goes On
Logic O/P from controller
Typically Off <2Vdc On >5Vdc
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Whole Cycle Firing/Burst Firing - Analog I/P

Cycle Time giving for 50% output
TON
TOFF
T
CYCLE
At 50% TON = TOFF
TCYCLE = TON + TOFF
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
For lesser disturbance on
mains you may increase the
cycle time
Typical 1 cycle to
256 cycles
approx 5 secs
Long cycle time can
be few mins
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Single Cycle Firing - Analog I/P

Cycle Time is 2 cycles at
50%
50% Power
T
CYCLE
33% Power
T
CYCLE
•Silicon carbide
•When element new the resistance is low and full voltage must only be applied for short bursts.
•As the elements heat up and or age the voltage can be sustained for longer periods.
•To prevent problems on new elements a power limiting must be used otherwise the element can shatter
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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TE 200, TC2000 & TC2001
Less Expensive than three leg control but when the
unit is off the non-controlled leg is at line potential
3 Wire Star
3 Wire Delta
TC2000,
TE200
or
TC2001
EUROTHERM
CONTROLS
TC2000,
TE200
or
TC2001
Ref: P
.ppt (14/05/2017) 8
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Phase Angle - Analog I/P

Firing equally delayed for each 1/2 cycle
Shown as 50%
On
Not widely used in Europe as there are problems with CE requirements.
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Load Types




Fixed Resistance - Any firing mode
Variable Resistance - Current limit or single
cycle
Transformer Coupled - Phase angle or burst
firing with delayed start. This reduces surge
currents. Will switch on at zero crossing point
of current.
Inductive as above
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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Load Types
EUROTHERM
CONTROLS
Ref: P
11
.ppt (14/05/2017)
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Single Phase - Constant Load Resistance
SSDS / RSDA
EUROTHERM
CONTROLS
TE 10S
Ref: P
12
.ppt (14/05/2017)
425S / 450
TC1027
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Single Phase - Variable Load Resistance
TE10A
EUROTHERM
CONTROLS
425A
Ref: P
13
.ppt (14/05/2017)
460
TC1028
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Three Phase - Constant Load Resistance
TC300
TC3000
RS3DA / RS3AA
EUROTHERM
CONTROLS
TE200S / TE200A
Ref: P
14
TC2000
.ppt (14/05/2017)
TC2001
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Three Phase - Variable Load Resistance
TC3001
TC2001
EUROTHERM
CONTROLS
Ref: P
15
.ppt (14/05/2017)
a
Continental
SSDA
EUROTHERM
CONTROLS
RSDA
Ref: Thyristors SRF .ppt
(14/05/2017)
RS3DA
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TU Series
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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TC Series
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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TE10S / TE10A
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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450 / 460
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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425S / 425A
EUROTHERM
CONTROLS
Ref: Thyristors SRF .ppt
(14/05/2017)
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