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Specialized - Thyratron ·Thyratron

SC21

Xenon negative-control thyratron for high-current grid-controlled rectifier service. Its massive filament supports heavy controlled gas discharge.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
4BZ
Socket code
IO
Base pins
4
Nominal heater
2.5 V / 21 A

Description

SC21 is the C6J/SC21 xenon thyratron, a negative-control triode-type switching tube for grid-controlled rectifier service. It uses a 2.5 V, 21 A directly heated filament and is rated for 750 V peak forward anode voltage, 1250 V peak inverse voltage, 77 A peak anode current, and 6.4 A average anode current.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
4BZ
Socket code
IO
Base pins
4
Nominal heater voltage
2.5 V
Nominal heater current
21 A
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

4BZ - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Thyratron

X-ray radiationInterelectrode capacitances
Max plate voltage
750 V
Max cathode current
77 A
Rectifier peak inverse voltage
1250 V
Rectifier nominal output current
6.4 A
Rectifier peak forward current
77 A
Rectifier forward voltage drop
9 V
Rectifier warm-up time
60 s

Xenon thyratron; forward/inverse anode ratings and grid-controlled rectifier characteristics are published.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1971 RCA HB3 Binder 2 of 7

Published operating points and test conditions from this source.

SECTION 1

Thyratron

Characteristics

  • Filament voltage nominal

    2.4 to 2.6 V

    AC or DC

  • Filament current nominal

    19 A to 23 A

    At 2.5 V

  • Anode voltage drop average

    9 V

    Beginning of life

  • Anode voltage drop maximum

    - to 12 V

    End of life

  • Grid control ratio

    210

    10000-ohm grid resistor; circuit returns to filament transformer center tap

Other

  • Minimum heating time before conduction

    60 to - s

  • Maximum deionization time

    - to 1000 µs

  • Maximum critical grid current

    - to 10 µA

  • Maximum commutation factor

    - to 0.66 V·A/µs²

    Averaged over first 350 V of inverse anode-voltage rise

  • Peak forward anode voltage maximum

    - to 750 V

    Grid-controlled rectifier service

  • Peak inverse anode voltage maximum

    - to 1250 V

    Grid-controlled rectifier service

  • Peak grid voltage maximum before conduction

    -100 to - V

  • Peak anode current maximum

    - to 77 A

  • Average anode current maximum

    - to 6.4 A

    Averaged over any period of 6 seconds

  • Average overload anode current maximum

    - to 77 A

    Overload Rating I; duration 0.5 s

  • Average overload anode current maximum

    - to 38.5 A

    Overload Rating I; duration 1 s

  • Average overload anode current maximum

    - to 19.2 A

    Overload Rating I; duration 2 s

  • Average overload anode current maximum

    - to 12.8 A

    Overload Rating I; duration 3 s

  • Average overload anode current maximum

    - to 9.6 A

    Overload Rating I; duration 4 s

  • Average overload anode current maximum

    - to 7.7 A

    Overload Rating I; duration 5 s

  • Average overload anode current maximum

    - to 12.8 A

    Overload Rating II; duration 3 s

  • Average overload anode current maximum

    - to 11.2 A

    Overload Rating II; duration 4 s

  • Average overload anode current maximum

    - to 10.3 A

    Overload Rating II; duration 5 s

  • Average overload anode current maximum

    - to 9.6 A

    Overload Rating II; duration 6 s

  • Fault anode current maximum

    - to 770 A

    Maximum duration 0.1 s

  • Ambient temperature minimum

    -55 to - °C

  • Ambient temperature maximum

    - to 75 °C

Capacitance

  • Grid-to-anode capacitance

    4 pF

    Approximate

  • Grid-to-cathode capacitance

    21 pF

    Approximate