Barksdale UNS-VA/SB4 사용 설명서 - 페이지 4

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Inductive Loads

Direct current (DC):

Connect recovery diode parallel to the load, see picture 4.

Polarity must ensure that the diode will inhibit at normal operating voltage and short-circuit the

opposite voltage peaks occurring when opening the switch.

Alternating current (AC): Connect an RC unit parallel to the switch, see picture 5.

Dimensioning of such an RC unit can be executed according to the nomogram shown in the picture:

Example 1:

Example 2:

If inrush current is critical, minimum

resistance should be determined by

bottom nomogram.

Example: inrush current 0.5 A

Example 1

Figure 6: Nomogram for the determination of contact arc-dimming for inductive loads

I = 0.1 A

U = 220 V

C = 0.001 mF

R = 340 Ohm

= 400 Ohm

min

Voltage in V

Example 2

Capacitive Loads and Lamp Loads

Increased inrush currents occur for capacitive loads and lamp loads. High inrush currents can lead

to disturbances – even to fusing of contacts. During wiring of charged capacitors (e.g. cable

capacities) a sudden discharge will occur. The discharge intensity depends on the capacity and

length of the supply cable to the switch to be regarded as series resistor.

The discharge current peak is largely reduced by a series resistor. Its size is determined by the

capabilities of the respective circuit. The series resistor should be as large as possible to limit the

discharge current to a permissible value. These criteria apply analogously to the charging of

capacitors, see picture 2.

Wiring lamp loads: The resistance value of cold lamp filaments (not switched on) is about ten times

smaller than that of switched on lamp filaments. When the lamp is being switched on the current

flow is for a short time ten times higher than in the glowing static state of the lamp. This tenfold

inrush current can be reduced to a permissible value by a series-connected current limiting

resistor. Parallel connection of a resistor to the switch is another option. The parallel resistor will

permanently preheat the filament while the lamp is switched off just so far that it does not yet glow.

Both protection systems result in the loss of power.

Use in Hazardous Locations

Type of protection "i" intrinsic safety

The level switches to be used in hazardous locations are principally designed for intrinsically safe

circuits i following the applicable regulations and marked by the words

plate.

They are only for use in an approved intrinsically safe circuit. The maximum values per circuit are

stated on the type label.

Contact Wiring and Color Code

Group 1 SPST

Group 2 SPDT

Terminal

white

blue

pink

grey

yellow

green

brown

Ex ia... on the type