- The voltage applied across the diode when it is reverse biased must always be lesser than the Peak Inverse Voltage (PIV) specified in the datasheet of the diode.
- During positive half cycle, diode-2 is reverse biased and similarly during negative half cycle, diode-1 is reverse biased. When a diode is reverse biased, it should be able to withstand the peak value (Vp = Vrms * 1.414) of the AC voltage applied across it.
- The current through the diode (load current) must be lesser than the maximum anode current (Ia) specified in the datasheet of the diode.
- The current flows through the diode only when it is forward biased. The maximum value of current through diode Imax = Vpeak / Rload.
- For safe operation, Imax < Ia max.
- However the diode can withstand non-repetitive surge currents for a very short time.
Choose the components and their ratings
SCR 1
SCR 2
Diode 1
Diode 2
Ammeter
Voltmeter
Kindly choose the components and their ratings and click "Verify" Button
Click here to view datasheets
Click here to learn how to design the circuit.
Available Components
Available SCRs
| SCR Name | PIV | If max | Ig max | Is max | Datasheet | |
|---|---|---|---|---|---|---|
| 1 | S4S1 | 400 V | 0.8 A | 1.0 A | 20 A for 16ms | S4S1 |
| 2 | H2P4M | 400 V | 2.0 A | 0.2 A | 20 A for 10ms | H2P4M |
| 3 | S6004V | 600 V | 4.0 A | 1.0 A | 30 A for 25ms | S6004V |
| 4 | SK006L | 1000 V | 6.0 A | 2.0 A | 100 A for 83ms | SK006L |
Available Diodes
| Diode Name | PIV | Vf | If max | Is max | Datasheet | |
|---|---|---|---|---|---|---|
| 1 | 1N4004 | 400 V | 1.0 V | 1.0 A | 30 A for 8.3ms | 1N4004 |
| 2 | CMF01 | 600 V | 2.0 V | 2.0 A | 30 A (50Hz) | CMF01 |
| 3 | PSC406 | 600 V | 2.0 V | 4.0 A | 14 A for 10ms | PSC406 |
| 4 | 6A10 | 1000 V | 0.9 V | 6.0 A | 400 A for 8.3ms | 6A10 |
How to choose the right components?
Diode
SCR
- All the design aspects of diode are applicable to SCR.
- Additionally, SCRs have another terminal (Gate).
- The gate current applied to the SCR must not exceed the maximum gate current (IGM) specified in the datasheet
- The power (voltage * current) applied to the gate terminal must not exceed the maximum gate power (PGM) specified in the datasheet
- By increasing the gate current of the SCR, the forward voltage drop of the SCR can be reduced.
Load resistance
- In this virtual lab setup, we assume we have a rheostat
- Current Rating of rheostat: (0 - 6) A
- Power rating of rheostat: 10,000 W
- Resistance Values: 10Ω to 1000Ω
- The load resistance must be chosen such that the load current will be less than the maximum anode current of the SCRs and diodes.
Load Inductance
- In this virtual lab setup, we assume we have a variable inductor
- Current Rating: (0 - 6) A
- Power rating: 10,000 W
- Inductance Values: 0 mH to 2000 mH
Voltmeter
- The output voltage of a semi-converter is pulsating DC voltage.
- To measure DC voltage, MC Voltmeters are used. MC voltmeters give the average value of the voltage.
- To have higher accuracy, do not choose voltmeters with very high range than actually needed.
- For example: To measure 450V DC, choosing 750V MC voltmeter will give inaccurate measurements. But choosing a 500V MC voltmeter will give accurate measurements.
Ammeter
- The SCRs and diodes in a semi-converter will block reverse current.
Hence the load current will be pulsating DC current. - To measure DC current, MC Ammeters are used.
MC ammeters give the average value of the current. - To have higher accuracy, do not choose ammeters with very high range than actually needed.
- For example: To measure 4A DC, choosing 7.5A MC ammeter will give inaccurate measurements. But choosing a 5A MC ammeter will give accurate measurements.