What's New - MD7 Series Surge Protectors with ATEX Approval

Figure 1. Ultra-slim MD7 Series surge protector

M-System’s MD7 Series is lightning surge protector for instrumentation signals, network and power supplies. Figure 1 illustrates the outer appearance. It has an ultra slim housing with a 7 mm (.28”) width. Sixteen (16) of the MD7 surge protectors mounted side by side are only 112 mm (4.41”) wide, allowing the user to reduce panel size and costs.

The MD7 series has thirteen (13) models approved for use in Zone 0 hazardous locations. These models are available to use for corresponding IIC Gas Group of Hydrogen and Acetylene. Details of intrinsically safe parameters are as shown in the Table 1.

CENELEC: Intrinsically safe (ATEX)
II 1G, Ex ia IIC^*; T4 and T5
^*Equipment intended for use in a Class I, Zone 0 area commonly has the intrinsically safe, "ia," classification.

Intrinsically safety is an essential requirement for equipment that will be installed on-site or in remote locations.

Table 1. Safety Parameters

Intrinsically Safe Parameter
Product name	Model	Ui (V)	Ii (mA)	Ci (nF)	Li (µH)
Standard Signal Line	MD7ST-60	60	any	5	0
Standard Signal Line	MD7ST-24	32	any	10	0
Two-wire Signal Loop	MD72W-55	60	150	5	150
	MD72W-32	32	150	10	150
	MD72W-16	16	150	35	150
	MD72W-07	7	150	50	150
Two-wire Signal Loop (2 channels)	MD72WD-32	32	any	15	0
	MD72WD-16	16	any	35	0
	MD72WD-07	7	any	50	0
Three-wire Signal Loop	MD73W	32	150	10	150
Pulse Signal	MD7PL	32	any	10	0
PROFIBUS-PA	MD7PA	32	any	5	0
FOUNDATION Fieldbus	MD7FB	32	any	5	0
Thermocouple	MD7TC	16	any	35	0
Potentiometer	MD7PM
Strain gauge	MD7LC
RTD	MD7RB	7	any	50	0
RS-485/RS-422	MD74R
LONWORKS	MD7LWA
Temp. ClassRange		Range		Pi (W) Parameter
T4		–25 to 40°C		1.3
		–25 to 60°C		1.2
		–25 to 80°C		1.0
T5		–25 to 40°C		1.0

Table 2. CENELEX / ATEX IS Data

	Linear Barrier			FISCO Supply
Ui (Vmax)	32 V			17.5 V
Ii (Imax)	any			400 mA
Ci	5 nF			5 nF
Li	0 µH			0 µH
Pi	Temp. Class	Range	Parameter	5.4 W
	T4	–25 to 40°C	1.3 W
		–25 to 60°C	1.2 W
		–25 to 80°C	1.0 W
	T5	–25 to 40°C	1.0 W

The IEC60079-10 international standard classifies hazardous locations according to the possible presence of dangerous gases. Zone 0, having the highest risk, is where an explosive atmosphere is expected to exist continuously or for very long periods of time.

The MD7PA for PROFIBUS-PA and MD7FB for FOUNDATION Fieldbus are ATEX approved with full FISCO^* (Fieldbus Intrinsically Safe Concept) compliance.

Ex ia EN 60079-11
Category 1G EN 60079-26

^*FISCO simplifies the rules governing energy storage in field cables, and makes more power available to the fieldbus trunk. This arrangement means more fieldbus instruments can be connected in the hazardous area, and allows users to spend less time justifying and documenting an installation’s safety.

Click on the model numbers in Table 1.