5-16 E6198B Switch/Load Unit User Manual
5 Using Load Cards and Loads
Protection Devices
MOV (Metal Oxide Varistor), or back-to-back zener diodes are
recommended for flyback voltage protection.
*
Refer to
Figure 5-10. Zener Diode, MOV (Metal-Oxide Varistor) or
Transzorb
®
devices mounted at RTx or RTy (2 required per load
- 1 at NC and 1 at NO) provide current path for the inductive
load flyback. Select the protection device so that it conducts at a
voltage higher than the UUT's internal protection. If the device's
internal protection fails, then the added external protection
conducts to protect the UUT and the load card.
Typical small MOV (3mm) axial lead mounted specifications are:
Continuous DC voltage: 220 V
Transient energy (10/1000mS)
â€
: 0.90 Joules (watt-seconds)
Transient peak current (8/20mS)
‡
: 100 Amperes
Varistor voltage @ 1.0mA DC: 300 Vdc Max
Maximum Clamping Voltage (8/20mS): 450 volts
Capacitance: 17 pF
Typical Transzorb
®
specifications are:
Breakdown voltage: 300 V max at 1mA
Reverse Standoff voltage: 250 volts
Maximum reverse leakage: 5 mA
Maximum peak pulse current: 5 A
Maximum Clamping voltage: 400 volts
Maximum temperature coefficient: 0.110%/°C
* The card was tested using a General Electric GE MOV II, MA series MOV.
Figure 5-10 Typical Agilent E6175A Load Card Flyback Protection Circuit
†10/1000mS refers to a standard pulse of 10mS rise and 1000mS to 50% decay of peak value.
‡ 8/20mS refers to a standard pulse of 8mS rise and 20mS to 50% decay of peak value.
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