Ceramic Over Voltage Gaps
OGP-Series,
PGP-Series, PB-Series
Perkin Elmer's Over voltage Spark Gaps are a family of rugged
ceramic-metal hermetically sealed switches for voltages ranging from 500V
to 100kV. These switches have peak current capabilities of up to 50 kA.
They are ideal for protecting equipment from damaging high voltage surges
when they are used in "crowbar" applications.
They are also suitable for capacitor switching
applications. The OGP-series offer the broadest operating range, while
the PGP and PB series offer fast switching for high dv/dt applications.
The PB series is intended for direct mounting on printed circuit boards.
Table
1.
Crowbar Service
OGP-Series
Spark Gap Ratings
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This table shows ratings for Perkin Elmer's OGP ceramic-metal overvoltage
spark gaps when they are used in crowbar service. Note that for each "family"
type, a range is shown for Static Breakdown Voltage (SBV); for any given
gap, there can be only a single value for SBV.
For rating purposes, crowbar service is defined as being single-shot or
very low repetition rate operations such that gap heating is nil. For
applications where the various discharge parameters simultaneously approach
the values shown, gap life will be on the order of 1000-5000 operations.
Longer life can be obtained when operating at reduced power levels; alternatively,
operation at higher levels is possible, but life will be reduced. For
applications involving repetitive operation such that gap heat ing is
significant, the ratings of Table 2 apply. For discharge conditions simultaneously
approaching the maximums shown, gap life is typically one million to five
million operations. Again, a trade off exists between discharge severity
and service life. |
| Family
Type (1) |
Available
Static
Breakdown Voltage Range
(Min-Max kV) (2) |
Maximum
Discharge Conditions (4) |
|
Peak Current (kA) |
Total
Conducted Charge per pulse (millicoulombs) |
OGP-57
OGP-62
OGP-64
OGP-44
OGP-49
OGP-75
OGP-35
OGP-83
OGP67,
OGP73
OGP-76
OGP-1501 |
1-9
1-9
1-9
9-25 (3)
2-25 (3)
10-30
8-42 (3)
8-42 (3)
30-65 (3)
40-120 (3)
12-120 (3)
|
5
5
5
5
7.5
20
50
25
20
50
50 |
200
200
200
200
400
500
1000
800
500
1000
1000 |
|
Table
1, Table 2 NOTES
1.
The general family type listed. Mechanical variations with differing
connections are shown in the accompanying drawing, these are designated
by the addition of another digit or\a letter to the b,c family number.
For example, the OGP-44 family includes the 44G, 441, 443, 444,
445, 446, 44L and 44R.
2. Each overvoltage gap is manufactured with a specific static
(or DC) breakdown voltage (SBV). This voltage can be set anywhere
within the available min-max range. The SBV is specified by the
addition of a dash number to the mechanical type number, giving
the SBV in kilovolts.
3. These units must be operated in a dielectric medium to prevent
external corona or breakdown: OGP-76, above 50kV; OGP-1501, above
35kV; OGP-44, above 15kV; OGP-67 and OP-73, above 40kV; OGP-49,
above 15kV; OGP-83 and OGP-35, above 20kV. Some of the more important
derating factors that determine the safe operating voltage in air
are the cleanliness of the tube's ceramic insulators, the rate of
rise of anode voltage, the dwell time at the operating peak anode
voltage, the pulse repetition rate, and ambient pressure, temperature,
humidity and contaminant level.
4. The ratings shown apply for single-shot service. Under these
maximum duty conditions, gap life is typically 1000-5000 operations.
5. For conditions approaching these maximum ratings, life is
typically one million to five million operations. Longer life can
be obtained when operating at reduced levels; alternatively, operation
at higher levels is possible, but life will be reduced.
6. Ib is the average current through the gap. It is equal to
the conducted charge per pulse x pulse repetition rate (prr). 7.
Ip is the RMS current through the cap. For rectangular current pulses,
Ip = Ib x peak current.
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Table
2.
Repetitive Switching Service
|
| Family
Type (1) |
Available
Static Breakdown Voltage Range (Min-Max kV) (2) |
Maximum
Discharge Conditions (5) |
|
Conducted
Charge per pulse
(millicoulombs)
|
Avg.
Current lb (mA, DC) (6)
|
RMS
(Current)
IP (A, AC) (7)
|
OGP-57
OGP-62
OGP-64
OGP-44
OGP-49
OGP-75
OGP-35
OGP-83
OGP67,
OGP73
OGP-76
OGP-1501 |
1-9
1-9
1-9
9-25 (3)
2-25 (3)
10-30
8-42 (3)
8-42 (3)
30-65 (3)
40-120 (3)
12-120 (3)
|
4
4
4
4
8
20
20
8
20
20
20 |
40
40
40
40
60
150
200
100
150
200
200 |
6
6
6
6
8
10
15
10
10
15
15 |
Table
3.
PGP and PB Spark Gap Ratings |
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This table shows ratings for Perkin Elmer's PGP and PB Series pulse overvoltage
spark gaps. These have been specifically designed to protect critical
components against damage caused by fast high voltage transients. The
dynamic breakdown voltage (the voltage at which the gap breaks down under
transient conditions) is a function of the rate of rise of the applied
voltage (dv/dt). In general, it will be higher for higher dv/dt.The breakdown
time ofthese gaps is much faster than that of conventional overvoltage
types, and their dynamic breakdown voltage is relatively close to their
static breakdown voltage over a wide range of operating conditions.
PGP
Series
In single-shot protection service, these gaps can divert a transient energy
as
high as 10 joules and conduct a total charge as high as 300millicoulombs.
Dynamic breakdown voltage is typically less than twice their static breakdown
voltage for applied voltage transients as fast as 300 kilovolts per microsecond.
PB
Series
Peak currents up to 1500 amperes with current rise times on the order
of 1-5 nanoseconds are possible. The small size of these devices makes
them well suited for use on circuit boards and in other applications where
space is restricted. For best results the gap should be tightly coupled
across the component to be protected. On nanosecond time scales, the inductive
drop across even a few inches of excess wiring can easily exceed the rated
turn-on voltage of the gap. Typical rating for inter-electrode capacitance
is 3 pf, dynamic voltage drop is 50 volts, and open circuit resistance
at 500 volts is 1000 megohms.
|
| |
Available
Static Breakdown Voltage Range (Min-Max kV) (2)
|
Maximum
Operating Standoff Voltage (2)
|
Dynamic
Breakdown DBV (typical)
|
Peak
Current (kA)
|
Conducted
Charge per pulse
(millicoulombs maximum) (5)
|
|
PGP Series
PGP-571
PGP-574
PGP-575
|
0.5-6 |
80%
of SBV |
180-200%
of SBV (3) |
10 |
300 |
|
PB Series
PB-23
PB-23A
PB-23C
PB-23D
|
0.5-5 |
80%
of SBV |
40 |
1.5 |
50 |
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Table
3 NOTES
1. The DC voltage at which the gap switches from the open to
the conducting state. (For any given gap, SBV has a single fixed
value).
2. The SBV of an individual gap may be +/-10% of its nominal
value. Therefore, the recommended maximum operating (standoff) voltage
is 80% of SBV.
3. The range shown is typical for dv/dt between 75 and 300 kV/us.
4. The maximum dynamic breakdown voltage is 1000 volts for gaps
having SBV between 500 and 750 volts. For higher SBV, DBV is approximately
1.3 times SBV.
5. Typical life at rated conducted charged is 500-1000 operations.
Life increases substantially at lower operating levels. When Ordering
All Overvoltage Gaps, Self Breakdown Voltage (SBV) must be specified.
Example: OGP-44G type gap with 15kV DC SBV must be specified as
OGP-44G-15. Contact Richardson for EG&G Application Notes and Complete
Specifications.
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When
Ordering All Overvoltage Gaps,
Self Breakdown Voltage (SBV) must be specified.
Example: OGP-44G type gap with 15kV DC
SBV must be specified as OGP-44G-15.
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