A very informative book

1. Power Semi – Conductor
Devices
Engr.Kashif Iqbal
Department of Electrical Engineering & Technology
Kashif.iqbaluet@gmail.com

2. Contents:
 Power Diodes
 Thyristors
 Power Transistors
 Snubber Circuit
 Comparison between Ideal and Practical Switch
 Bipolar Junction Transistor (BJT)
 BJT Darlington Pair
 Metal Oxide Silicon Field Effect Transistor MOSFET
 Insulated Gate Bipolar Transistor (IGBT)
 GTO
2

3. Power Semi – Conductor Devices
 These devices act as switches without any mechanical movement.
 Few of the Power Devices are
1. Power Diodes
2. Power Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET)
3. Power Bipolar -Junction Transistor(BJT)
4. Insulated-Gate Bipolar Transistor (IGBT)
5. Thyristors (SCR, GTO, MCT, IGCT)
3

4. Power Semi – Conductor Devices Ratings 4

5. Semiconductor Symbols 5

6. Comparison between Ideal and Practical Switch
Ideal Switch Practical Switch
Block arbitrarily large forward and reverse
voltage with zero current flow when off.
Finite blocking voltage with small current
flow during turn-off.
Conduct arbitrarily large currents with zero
voltage drop when on.
Finite current flow and appreciable voltage
drop during turn-on (e.g. 2-3V for IGBT).
Switch from on to off or vice versa
instantaneously when triggered.
Requires finite time to reach maximum
voltage and current. Requires time to turn on
and off.
Very small power required from control source
to trigger the switch.
In general voltage driven devices (IGBT,
MOSFET) require small power for triggering.
GTO requires substantial amount of current to
turn off.
6

7. Ideal Characteristics of a Power Device
 Arbitrarily large forward and reverse voltages are blocked with zero currentflow
during OFF condition.
 No conduction losses i.e. large current flows with no voltage drop duringON
condition.
 ON – OFF switching is instantaneous without any delay.
 For triggering action, negligible power is required.
7

8. Power Diode:
 Power Diode is a two terminal P – N junction semiconductor device.
 The two terminals are anode (A) and cathode (K/C).
 If terminal A experiences a higher potential compared to terminal K, the device is said
to be forward biased and a forward current will flow from anode tocathode.
 This causes a small voltage drop across the device (<1V) called as forward voltage
drop(V f), which under ideal conditions is usuallyignored.
 By contrast, when a diode is reverse biased, it does not conduct and the diode then
experiences a small current flowing in the reverse direction called the leakage current.
It is shown below in the V-I characteristics of the diode.
 The structure of a power diode is different from a signal diode.
8

9. Power Diode – Structure :
 The complexity in power diode is to accommodate for the high power applications.
 Power diodes find applications in rectifier circuits, freewheeling or fly backdiodes.
 There is heavily doped n+ substrate (cathode) with doping level of1019/cm3
 Lightly doped n – epitaxial layer is grown, also known as driftregion.
 Anode is formed by the heavily doped p+ region.
 The breakdown voltage depends on the thickness of the n –layer.
 The n – layer is absent in signal diodes.
9

10. Power Diode:
 Diodes block voltage in reverse direction and allow current in forwarddirection.
 They start conduction once the voltage in the forward direction goes beyond a certain
value.
 I – V Characteristics and Reverse Recovery Characteristicsschematic
10

11. Power Diode
 When a diode is forward biased, it conducts current with a small forward voltage of 0.2
– 3 V across it.
 When reversed, a negligible small leakage current (µA to mA) flows until the reverse
breakdown occurs.
 When a diode is switched quickly from forward to reverse bias, it continues to conduct
due to the minority carriers which remains in the p – n junction.
 The minority carriers require finite time i.e. t rr (reverse recovery time) to recombine
with opposite charge and neutralize.
11

12. Thyristor
 4 – layer semiconductor device of alternating p- and n- material.
 Two – states: ON & OFF.
 Silicon Controlled Rectifier: SCR
 Trade Name of Thyristors commercialized by General Electric in 1957.
 4-layered 3-terminal device.
 Have the highest power handling capability.
 Rating of 1200V / 1500A.
 Switching Frequency: 1KHz to 20KHz.
12

13. Symbol & Construction
 Alternately N-type or P-type material, for example P-N-P-N.
 The control terminal, called the gate, is attached to p-type material near to the cathode.
13

14. Characteristics of Thyristors
 When the anode is at a positive potential VAK with respect to the cathode with no
voltage applied at the gate, junctions J1 and J3 are forward biased, while junction J2 is
reverse biased. As J2 is reverse biased, no conduction takes place.
 Now if VAK is increased beyond the breakdown voltage VBO of the thyristor, avalanche
breakdown of J2 takes place and the thyristor startsconducting.
 If a positive potential VG is applied at the gate terminal with respect to the cathode, the
breakdown of the junction J2 occurs at a lower value of VAK. By selecting an
appropriate value of VG, the thyristor can be switched into the on statesuddenly.
14

15. Thyristors Specifications: 15
 Forward-break over voltage, VBR (F):
This is the voltage at which the SCR
enters the forward-conduction
region.
 Holding current, IH: This is the value
of anode current below which the
SCR switches from the forward-
conduction region to the forward-
blocking region.
 Gate trigger current, IGT: This is the
value of gate current necessary to
switch the SCR from the forward-
blocking region to the forward-
under specified
conduction region
conditions.

16. Characteristic Curve – Thyristor 16

17. Ideal Switch
 An ideal switch behaves like a diode.
 3 – states: Forward Blocking; Forward Conduction; Reverse Blocking.
 Gate signal switches ON the thyristor.
17

18. Types of Thyristors
 Unidirectional thyristor: The thyristors which conduct in forward direction only are
known as unidirectional thyristors
Example: SCR- Silicon Controlled Rectifier; LASCR-Light Activated Silicon Controlled
Rectifier
 Bidirectional Thyristor: The thyristors which can conduct in forward as well as in
reverse direction are known as bidirectional thyristor
Ex: TRIAC - TRIode ACswitch
 Triggering Devices: The devices which generate a control signal to switch the device
from non-conducting to conducting state are known as triggeringdevices.
Ex: Diode AC Switch-DIAC,
18

19. Static Characteristics
 Blocking when reverse biased, no matter if there is gate current or not.
 Conducting only when forward biased and there is triggering current applied to the
gate.
 Once triggered on, will be latched on conducting even when the gate current is no
longer applied.
 Turning off: decreasing current to a near zero with the effect of external powercircuit.
 If VAK is further increased to a large value, the reverse biased junction will
breakdown due to avalanche effect resulting in a large current through the device.
 The voltage at which this phenomenon occurs is called the forward breakdown
voltage (VBO)
19

20. Two Important Current Terms
LATCHING CURRENT (IL)
After the SCR has switched on, there is a minimum current required to sustain
conduction even if the gate supply is removed. This current is called the latching
current. associated with turn on and is usually greater than holdingcurrent.
HOLDING CURRENT (IH)
After an SCR has been switched to the on state a certain minimum value of anode
current is required to maintain the Thyristor in ON state. If the anode current is reduced
below the critical holding current value, the Thyristor cannot maintain the current
through it and turns OFF.
20

21. Effects on Gate current on Forward Blocking
Voltage
21

22. V – I Characteristics 22

23. Gate Triggering
 Positive signal is applied at Gate terminal.
 By this, thyristor can be triggered much before break over voltage is reached.
 Conduction period can be controlled by varying Gate signal.
 Signal is applied between Gate and Cathode.
 When a positive voltage is applied at the gate terminal, charge carriers are injected in
the inner P-layer, thereby reducing the depletion layer thickness.
 As the applied voltage increases, the carrier injection increases, therefore the voltage at
which forward break-over occurs decreases.
23

24. Types of Gate Triggering
Three types of signals are used for gate triggering.
1. DC Gate Triggering
2. AC Gate Triggering
3. Pulse Gate Triggering
24

25. DC Gate Triggering
 A DC voltage of proper polarity is applied between gate and cathode ( Gate terminal is
positive with respect to Cathode).
 When applied voltage is sufficient to produce the required gate Current, the device
starts conducting.
 One drawback of this scheme is that both power and control circuits are DC and there
is no isolation between the two.
 Another disadvantages is that a continuous DC signal has to be applied. So gate power
loss is high.
25

26. AC Gate Triggering
 AC gate triggering is most commonly used as it provides proper isolation.
 Firing angle control is obtained by changing the phase angleconveniently.
 Here AC source is used for gatesignals.
 This scheme provides proper isolation between power and controlcircuit.
 Drawback of this scheme is that a separate transformer is required to step down AC
supply.
26

27. Pulse Gate Triggering
 Pulse triggering is the most popular.
 Pulse transformer is used for isolation.
 No need to apply continuous signal, therefore lessloss.
 Sequence of high frequency pulse called “carrier frequency gating” isapplied.
 In this method the gate drive consists of a single pulse appearing periodically (or) a
sequence of high frequency pulses.
 This is known as carrier frequency gating.
 A pulse transformer is used forisolation.
 The main advantage is that there is no need of applying continuous signals, so the gate
losses are reduced.
27

28. Switching Characteristics 28

29. Turn on Switching Characteristics
 Turn – On
29
t d = delay time; t r = rise time; t p = peak time

30. Turn off Switching Characteristics
 Turn Off
30
t rr = reverse recovery time; t gr = gate recovery time

31. Firing Angle
 Firing Angle 𝜶: It is the angle after which the thyristor fires of conducts. It is normally
done by either analog, digital or microprocessor controller circuits which sends the
desired pulse to the thyristor gate drive circuit that will produce the actual gate drive
pulse.
 Varying this angle changes the effective RMS values of voltage and current and hence
power.
31

32. Thyristor Protection
For reliable and satisfactory operation, the specified ratings of SCR should
not exceed due to overload, voltage transients and other abnormalities.
Due to reverse process in SCR during turn OFF, the voltage overshoot occurs.
In case of short circuit, a large current flows through SCR which may damage
the device.
32

33. Snubber Circuit – dv/dt protection
 A snubber circuit comprises a series combination of capacitor and resistor connected
across the SCR.
 It sometimes also consists of an inductor in series with SCR to prevent high di/dt.
 The value of the resistor is few hundred ohms.
 With the switch closed, the voltage that appears across the SCR is bypassed to the RC
network as the capacitor acts as a short circuit, thus reducing the voltage tozero.
 With increment of time, the capacitor gets charged up at a slow rate which is
significantly small to be able to turn on the SCR.
 Thus the dv/dt rating is always way lesser than the maximum dv/dt ratings.
33

34. Over Voltage Protection
 The major reason for SCR failure is overvoltage as this transient overvoltage leads to
unscheduled turning ON of the SCR and sometimes the reverse transient voltage
exceeds the reverse breakdown voltage.
 The reasons of this overvoltage may be commutation, chopping or lightening.
 Internal Overvoltage: During turn OFF, a reverse current continues to flow through the
SCR after the anode current is decreased to zero. As this decaying current flows at a
faster rate, due to inductance of the circuit, the high di/dt produces a high voltage
which if crosses the SCR ratings will damage the SCR permanently.
34

35. Merits & Demerits of Thyristors
 Merits of SCR:
1. SCRs with high voltage and current ratings are available.
2. On state losses in SCRs are reduced.
3. Very small amount of gate drive is required since SCR is a regenerative device.
 Demerits of SCR:
1. Gate has no control after the SCR is turned ON.
2. External circuits are required to turn OFF the SCR.
3. Operating frequencies are very low.
4. Snubber circuits are required for dv/dt protection.
35

36. Applications of Thyristor:
 High Current High VoltageApplications.
 Controlling alternating currents, where the change of polarity of the current causes the
device to switch off automatically; referred to as Zero Cross operation.
 Phase angle triggered controllers, also known as phase firedcontrollers.
 “Circuit breaker" or “Crowbar" to prevent a failure in the power supply from damaging
downstream components, by shorting the power supply output toground.
 Load voltage regulated by thyristor phase control.
 Red trace: load voltage
 Blue trace: trigger signal.
36

37. Power Transistor Types
 Bipolar Junction Transistor (BJT)
 Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
 Insulated Gate Bipolar Transistor (IGBT)
37

38. Transistors 38

39. Bipolar Junction Transistor 39
 Three terminal, three layer, two junction semiconductor device.
 Emitter, Base and collector form the three terminals.

40. Structure - BJT 40
 The n – layer is added in power BJT which is known as driftregion.
 There are alternating P – N – P – Nlayers.
 The characteristics is determined by the doping level in each layer and the thickness of
the layers.
 The thickness of the drift region determines the breakdown voltage of the Power
transistor.

41. V – I Curve - BJT 41
 The major differences between signal and power BJT are Quasi saturation region &
secondary breakdown region.
 The Quasi saturation region is available only in Power transistor characteristic not in
signal transistors.
 It is because of the lightly doped collector drift region present in PowerBJT.
 The primary breakdown is similar to the signal transistor's avalanche breakdown.
 Operation of device at primary and secondary breakdown regions should be avoided as
it will lead to the catastrophic failure of the device.

42. V – I Curve - BJT 42

43. Rating - BJT 43
 Ratings:
 Voltage: VCE <1000,
 Current: IC < 400A.
 Switching frequency up to 5kHz.
 Low on-state voltage: V CE(sat): 2-3V
 Low current gain (𝜷 <10). Need high base current to obtain reasonable IC .

44. BJT: NPN & PNP 44

45. BJT Darlington pair
𝑰𝑪
𝑰𝑩𝟏
 𝜷 = = 𝑰𝑪𝟏+𝑰𝑪𝟐
𝑰𝑩𝟏 𝑰𝑩𝟏 𝑰𝑩𝟏
= 𝑰𝑪𝟏
+ 𝑰𝑪𝟐
= 𝜷 𝟏 +
𝑰𝑪𝟐
𝑰𝑩𝟐
𝑰𝑩𝟐
𝑰𝑩𝟏
 = 𝜷𝟏 + 𝜷𝟐
𝑰𝑩𝟏+𝑰𝑪𝟏
𝑰𝑩𝟏
𝟏
= 𝜷𝟏 + 𝜷𝟐. 𝟏 + 𝜷𝟏 = 𝜷 + 𝜷𝟐 +𝜷𝟏𝜷𝟐
 Normally used when higher current gain is required.
45

46. Metal Oxide Silicon Field Effect
Transistor (MOSFET)
 Three terminal (Gate, Drain, Source), four layer unipolar device.
 Voltage Driven Device, Simple Driver Circuit
 Majority carrier device, Fast Switching Speed
 Gate is electrically isolated from source giving MOSFET good input impedance and
good capacitance.
 Drain to source resistance has positive temperature coefficient hence self protective.
 Very low On resistance and no junction voltage drop when forward boased.
46

47. MOSFET – Types 47

48. Difference between Depletion MOSFET vs
Enhancement MOSFET
Figure show the construction of depletion type MOSFET. Due to its construction it
offers very high input resistance (about 1010 to 1015). Significant current flows for
given VDS at VGS of 0 volt.
Figure show the construction of enhancement type MOSFET.Here continuous channel
does not exist from source to drain. Hence no current flows at zero gate voltage. When
positive voltage is applied to the gate, it will induce a channel between Drain and
source terminal.
48

49. MOSFET – Ratings
 Ratings:
 Voltage VDS < 500 V,
 Current IDS < 300A.
 Devices (few hundred watts) may go up to MHz range.
 Frequency f >100 KHz for some low power.
 Turning on and off is very simple.
– To turn on: VGS = +15V
– To turn off: VGS = 0 V and 0V to turn off.
 Gate drive circuit is simple.

50. MOSFET Features
 Basically low voltage device .
 High voltage device are available up to 600V but with limitedcurrent.
 Can be paralleled quite easily for higher current capability.
 Internal (dynamic) resistance between drain and source during on state, R DS(ON), ,
 Limits the power handling capability of MOSFET.
 High losses especially for high voltage device due to R DS(ON) .
 Dominant in high frequency application (>100kHz).
 Biggest application is in switched-mode power supplies.
50

51. MOSFET Characteristics
 The current equation for MOSFET is givenas
𝐷
𝐼 = 𝑢 𝐶
𝑊
𝑉
1
𝑛 𝑜𝑥
2
𝑉𝐺𝑆 − 𝑉𝑇𝐻 𝐷𝑆 −
2
𝑉𝐷𝑆
2
un = Mobility of the electrons; Cox = Capacitance of the oxide layer; W = Width of the gate area;
L = Length of the channel; VGS = Gate to Source voltage; VTH = Threshold voltage; VDS = Drain to Source
voltage.

52. MOSFET Selection Factors
 To select a MOSFET for a particular application, following parameters have to be
considered from the device datasheet
1. Maximum Drain to Source voltage (VDSS)
2. On-state drain to source resistance RDS(ON)
3. Drain Current ID
4. Gate to source VoltageVGS
5. Input Capacitance 𝐶𝑖𝑠𝑠
6. Power Dissipation PD

53. Comparison – BJT vs MOSFET
BJT MOSFET
It is a Bipolar Device It is a Unipolar Device
Current control Device Voltage control Device.
Output is controlled by controlling base current Output is controlled by controlling gate voltage
Negative temperature coefficient Positive temperature coefficient
So paralleling of BJT is difficult. So paralleling of this device is easy.
Drive circuit is complex. It should
provide constant current(Base current)
Drive circuit is simple. It should provide
constant voltage(gate voltage)
Losses are low. Losses are higher than BJTs.
So used in high power applications. Used in low power applications.
BJTs have high voltage and current ratings. They have less voltage and current ratings.
Switching frequency is lower than MOSFET. Switching frequency is high.

54. Insulated Gate Bipolar Transistor – IGBT
 IGBTs are preferred devices for voltages above 300V and below5kV.
 Three terminal device: Gate, Emitter, Collector.
 They are turned on and off by applying low voltage pulses to theirgate.
 Combination of BJT and MOSFET characteristics.
 Superior on – state characteristics, good switching speed and excellent safe operating
area (SOA).
 Advantage: High current capability of BJTs and easy control of MOSFET.

55. Insulated Gate Bipolar Transistor
 IGBTs are preferred devices for voltages above 300V and below 5kV.
 They are turned on and off by applying low voltage pulses to theirgate.
 Combination of BJT and MOSFET characteristics.
 Gate behaviour similar to MOSFET - easy to turn on and off.
 Low losses like BJT due to low on-state Collector - Emitter voltage (2-3V).
 Ratings: Voltage: V CE < 3.3kV, Current,: I C < 1.2 kA currently available.
 Latest: HVIGBT 4.5 kV/1.2 kA.
 Switching frequency up to 100 KHz.
 Typical applications: 20-50 KHz.

56. IGBT Equivalent Circuit

57. IGBT Characteristics Curve

58. IGBT – Merits & Demerits
 Merits
1. Voltage controlled device
2. Less On state loss
3. High switching frequency
4. Gate has full control over operation
5. Flat temperature coefficient.
 Demerits:
1. Static charge problem.
2. Costlier than BJT and MOSFET.

59. IGBT – Comparison
Device
Characteristic
Power
Bipolar
Power
MOSFET
IGBT
Voltage Rating High > 1kV High <1kV Very High >1kV
Current Rating High > 500A Low <200A High >500A
Input Drive
Current, hFE
20-200
Voltage, VGS
3-10V
Voltage, VGE
4-8V
Input Impedance Low High High
Output Impedance Low Medium Low
Switching Speed Slow (uS) Fast (nS) Medium
Cost Low Medium High

60. Gate turn-off Thyristor (GTO)
 Behave like normal thyristor, but can be turned off using gatesignal
 However turning off is difficult.
 Need very large reverse gate current (normally 1/5 of anode current).
 Gate drive design is very difficult due to very large reverse gate current at turnoff.
 Ratings: Highest power ratings switch:
 Voltage: V AK < 5 kV; Current: I A < 5 kA. Frequency < 5 KHz.

61. Gate turn-off Thyristor (GTO)
These are capable not only to turn ON the main current with a gate drive
circuit, but also to turn it OFF. A small positive gate current triggers the GTO
into conduction mode and also by a negative pulse on the gate, it is capable
of being turned off.
The gate current required to turn off the GTO is relatively high. For example,
a GTO rated with 4000V and 3000A may need -600A gate current to switch
it off. Due to this large negative current, GTOs are used in low power
applications.
During the conduction state GTO behaves just like a thyristor with a small
ON state voltage drop. The GTO has faster switching speed than the thyristor
and has higher voltage and current ratings than the power transistors.

62. Construction - GTO
 Almost similar to SCR.
 In this, n + layer at the cathode end is highly doped to obtain high emitter efficiency.
 Due to this, breakdown voltage of the J3 junction is low (20 to 40V).
 The doping level of p type gate is highly graded as trade off between high emitter
efficiency (low doping required) and good turn off properties (high dopingrequired).

63. Construction - GTO
 Junction between p+ anode and N base is called anode junction.
 Heavily doped p+ anode region is required to obtain high efficiency anode junction so
that a good turn ON properties is achieved .
 But turn Off property is affected.
 This problem is solved by introducing heavily doped n+ layers at regular intervals in p+
anode layer.
 So this N+ layer makes a direct contact with N layer at junction J1. This cause the
electrons to travel from base N region directly to anode metal contact without causing hole
injection from P+ anode. This is called anode shorted GTO structure.
 But reverse blocking capacity of GTO is reduced and speeds up turn Off mechanism.

64. Working - GTO
 The Gate turn off thyristor (GTO) is a four layer PNPN power semiconductor switching
device that can be turned on by a short pulse of gate current and can be turned off by a
reverse gate pulse.
 This reverse gate current amplitude is dependent on the anode current to be turnedoff.
 There is no need for an external commutation circuit to turn it off.
 So inverter circuits built by this device are compact andlow-cost.
 The device is turned on by a positive gate current and it is turned off by a negative gate
cathode voltage.

65. GTO Characteristics Curve

66. GTO V – I Characteristics:
 It is similar to SCR during turn on.
 The 1st quadrant characteristics are similar to that ofSCR.
 Latching current and holding current are considerably higher thanSCR.
 The gate drive can be removed if anode current is more than the holding current.
 It is though not recommended as cathode is subdivided into small finger elements
causing the anode current to go below the holding current hence destroying thedevice.
 GTO is turned off by applying reverse gate current in either ramp or step mode.
 The dashed line in the figure shows i-v trajectory during the turn OFF for an inductive
load.
 dV/dt triggering is avoided by placing a rated resistor between gate and cathode or by
means of a reverse bias voltage.

67. GTO V – I Characteristics:
 A symmetric GTO has higher reverse blocking capability than an asymmetric type.
 After a small reverse voltage (20 to 30 V) GTO starts conducting in the reverse
direction due to anode short structure.

68. GTO Turn OFF Current Gain:
 The Turn Off Current Gain of a GTO is defined as the ratio of anode current prior to
turn off to the negative gate current required for turnoff.
 It is typically very low (4 or 5).
 It means a 6000Arating GTO requires 1500Agate current pulse.
 However, the gate pulse duration and the power loss due to the gate pulse issmall.
 It can be supplied by low voltage power MOSFETs.
 This gate turn off capability is advantageous because it provides increased flexibility in
circuit application.
 Now it becomes possible to control power in DC circuits without use of elaborated
commutation circuitry.

69. Summary GTO
 Advantages of GTO:
1. High blocking voltage capabilities.
2. High over current capabilities during turn off. .
3. Exhibits low gate currents.
4. Fast and efficient turn off.
5. Better static and dynamic dv/dt capabilities.
6. Enhanced Safe Operating Area during turn off.
 Disadvantages:
1. Magnitude of latching, holding currents is several times more than thyristors.
2. On state voltage drop and the associated loss is more.
3. Due to multi cathode structure of GTO, triggering gate current is higher than that required
for normal SCR.
4. Gate drive circuit losses are more.
5. Its reverse voltage blocking capability is less than the forward voltage blocking capability.

70. Summary GTO
 Applications of GTO:
1. Motor drives,
2. static VAR compensators (SVCs)
3. AC/DC power supplies with high power ratings.
4. DC circuit breakers
5. Induction heating
6. Low power applications.
7. DC choppers.

71. Insulated Gate-Commutated Thyristor (IGCT)
 Among the latest Power Switches.
 Conducts like normal thyristor (latching), but can be turned off using gate signal,
similar to IGBT turn off; 20 V issufficient.
 Power switch is integrated with the gate-drive unit.
 Ratings:
Voltage: V AK < 6.5 kV; Current: I A < 4kA.
 Frequency < 1 KHz. Currently 10kV device is beingdeveloped.
 Very low on state voltage: 2.7V for 4kAdevice.

72. Insulated Gate-Commutated Thyristor (IGCT)
Specifications GTO IGCT
Full Form Gate Turn-Off Thyristor
Insulated Gate Commutated
Thyristor
Advantages
• Controlled turn-off ability.
•Relatively high overload
capacity.
• Series connection
possibility.
•Working frequency of
hundreds of Hz.
• Controlled turn-off ability.
•Relatively high overload
capacity.
• Low on-state losses.
• Working frequency of kHz.
Disadvantages
• Higher on-state losses.
• High control power.
Applications
• High power drives
• Static compensators
• Continuous supply sources
• Induction heating sources
• High power drives
•Supply inverter sources for DC
transmissions
• Big frequency converters