Lightning Protection Issues

Transient Voltage Suppression Devices

Data lines protection

Surgector
Metal oxide varistor
Avalanche diode

Telecommunications primary circuits

Sugector
Metal oxide varistor
Gas tube

Telecommunications secondary circuits

Surgector
Avalanche diode

AC power lines

Metal oxide varistor

DC power & automotive applications

Surgector
Metal oxide varistor
Avalanche diode

With-in circuit applications

surgector
Metal oxide varistor
Avalanche diode

Comparison of Surge Suppression devices

(ųs = microsecond)
(markings: + means positive feature, - means negative feature, * means other information)

Surgector

+ Ideal for datacom and telecom
+ Leakage: < 50 nA
+ Shunt capacitance: < 50 pF
+ Sub nanosecond response
+ Lifetime infinite @200 Amps, 8x20 uS pulse shape
+ Failure mode: short circuit
- Cannot be used with DC circuits with current more than holding current
- Low surge current capability 200 Amps @ 8x20 uS
- Limited AC line protection
* High-input impedance until breakdown (low leakage)
* Repeatable breakdown/threshold voltage
* High-surge current-handling capability
* Withstand and respond to rapidly recurring surges
* Fast recovery to high impedance (turn-off)
* Dual polarity protection
* No degradation of essential characteristics with use

Metal-oxide varistor (MOV)

+ Ideal for AC power line; suitable for low-voltage logic
+ Sub nanosecond response
+ Up to 70 000 Amps surge
+ Lifetime @ 100 Amps, 8x20 uS pulse shape: 1000 surges
+ Failure mode: short circuit
- Shunt capacitance >500 pF
- Leakage approximately 10 micro amps
- Clamp voltage goes up with current
* Wide voltage range
* Wide energy range
* Excellent clamp ratio
* Fast response time
* Low standby
* Power
* No follow-on current
* UL recognized

Avalanche diode

+ Ideal for low-voltage logic protection
+ Sub nanosecond response
+ Lifetime @ 50 Amps, 8x20 uS pulse shape: infinite
+ Shunt capacitance: 50 pF
+ Failure mode: short circuit
- Low surge capability: 50 Amps @ 8x20 uS pulse shape
- Leakage approximately 10 micro amps

Gas tube

+ Wide use in telecom for primary protection
+ High surge capability: > 20 000 Amps
+ Leakage: Pico amps
+ Shunt capacitance: < 1 pF
+ Lifetime @ 500 Amps, 8x20 uS pulse width: 200 surges
- Response time: < 5 microseconds
- Failure mode: open circuit
- Follow-on current because of "crowbar"

Sources

GE/RCA Transient Voltage Suppressors,

GE/RCA/Intersil Semiconductors

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Metal Oxide Varistors - Definitions

Definition of Terms - (according to IEEE specifications C62.33)

Rated RMS Voltage, Rated DC Voltage: The maximum designated values of power system voltage that may be applied continuously between the terminals of a device.
Varistor Voltage: Test characteristic that is used to classify varistors by type. A test current of 1mA DC is typically used to determine varistor voltage classification type. Varistor voltage clamping characteristics can be defined at various test levels.
Rated Peak Single Pulse Transient Current: Maximum surge current, 8/20µs waveform which a varistor is rated to withstand for a single surge.
Rated Single Pulse Transient Energy: Maximum allowable energy for a single impulse (see specified waveforms).
Maximum Clamping Voltage: Measured peak voltage across the device terminals when a current impulse of specified amplitude and waveform is conducted through the varistor.
Typical Capacitance: Typical capacitance values are measured at a test frequency of 1KHZ.

Power Dissipation Ratings

Disc Size Pm-watts Disc Size Pm-watts Disc Size Pm-watts

5mm ( < 50 VAC ) 0.01 14mm ( < 50 VAC ) 0.10 32mm 1.60

5mm ( > 50 VAC ) 0.15 14mm ( > 50 VAC ) 0.60 40mm 2.10

7mm ( < 50 VAC ) 0.02 18mm ( > 50 VAC ) 0.80

7mm ( > 50 VAC ) 0.25 20mm ( < 50 VAC ) 0.20

10mm ( < 50 VAC ) 0.05 20mm ( > 50 VAC ) 1.00

10mm ( > 50 VAC ) 0.40

General Characteristics

Storage Temperature - 55° C to + 125° C

Operating Surface Temperature 125° C

Operating Ambient Temperature - 55° C to + 85° C (without derating)

Maximum Voltage-Temperature Coefficient < -0.01 % / °C

Insulation Resistance 1000 Megohm min.

Hi POT (Leads to Case, 1 min.) 2500 VDC

Typical Response Time < 15 nsec.

Epoxy Rating 94 V-0

Current/Energy Derating (>85°C) - 2.5 % / °C

DC Leakage Current 200µa Max (at rated DC working voltage)

Solder ability MIL STD 202F

Failure Criteria Voltage change of +/- 10% from initially measured varistor voltage.

Part Marking

Example: 5D241K

5

D

241

K

(1)

(2)

(3)

(4)

(1) Disc Diameter

5 = 5mm, 7 = 7mm, 10 = 10mm, 14 = 14mm, 18 = 18mm, 20 = 20mm

(2) Type

D = Standard
E = High Energy

(3) Varistor Voltage

241 = 24 x 10¹ = 240 (DC Volts)

(4) Tolerance

J = 5%, K = 10%, M = 20%

* - Parts will be marked Sincera. (This is the brand name for Walsin varistors.)

Part Number Code

Example: VZ10D241KBOCX

V

Z

10

D

241

K

B

O

C

Y

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(1) Series

V = Varistor

(2) Type

Z = Zinc Oxide

(3) Disc Diameter

5 = 5mm, 7 = 7mm, 10 = 10mm,
14 = 14mm, 18 = 18mm, 20 = 20mm

(4) Type

D = Standard
E = High Energy

(5) Varistor Voltage

241 = 24 x 10¹ = 240 (DC Volts)

(6) Tolerance

J = 5%, K = 10%, M = 20%

(7) Packing Code

B = Bulk Pack
(For taped parts packing code, see Taping Specifications.)

(8) Lead Configuration

S = Straight, O = Outward Crimp
I = Inward Crimp
L = Inline Crimp
(10mm, 14mm, 18mm,20mm disc diameter)
In-line crimp code "L" is not necessary in voltage 320VAC and higher.
In-Line crimp is standard for these voltage types.

(9) Lead Cutting

A = 4.0 ± 1.0mm (.16" ± .04")
(Crimped lead for 5mm, 7mm disc diameter)
B = 6.5 ± 1.0mm (.26" ± .04")
(Crimped lead for 5mm, 7mm disc diameter)
C = 4.5 ± 1.5mm (.18" ± .06")
(Crimped lead for 10mm, 14mm disc diameter)
D = 6.5 ± 1.5mm (.26" ± .06")
(Crimped lead for 10mm, 14mm , 18mm, 20mm disc diameter.)
E = 4.0 ± 1.0mm (.16" ± .04")
(Straight lead for all types)
F = 5.0 ± 1.0mm (.2" ± .04")
(Crimped lead for 10mm, 14mm disc diameter)
(For lead length reference points see
Standard Lead Modifications).

(10) Lead Spacing

Y = 7.5mm (0.3") lead spacing.
(For 20mm disc diameter only.)

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