Flameproof / intrinsically safe (12Vdc @ 500Ma) power supply with 120/240Vac input (other input voltages available).
The main transformer and relays (MineWatch PS21-R_ PS21-RD) are housed inside SG cast iron flame-proof enclosure with 6 FLP entries for supply and control cables. The MineWatch PS21-B; PS21-BD; PS21-BD/B also includes a sheet steel intrinsically safe battery enclosure. All variants have a sheet steel intrinsically safe terminal chamber for connecting the 12vdc to intrinsically safe controllers and/or sensors as a stand- alone unit; alternatively, the MineWatch PS21 can be directly mounted to a MineWatch PC21 intrinsically safe controller to provide a composite unit.
The PS21 and PS21-D have 12vdc outputs that are regulated to maintain the output voltage to a minimum of 11.5v up to the full load capacity of 500mA.
The MineWatch PS21-B; PS21-BD; PS21-BD/B will maintain this output at full load for an 8 hour period. The MineWatch PS21-B and PS21-BD also contains an intrinsically safe opto- output to indicate to the intrinsically safe controller when the power supply has changed from mains to battery. The PS21-BD/B gives an Intrinsically Safe Analogue output proportional to the Battery voltage status to be used on an approved monitoring system.
In the case of the MineWatch PS21-R and PS21-RD, up to 6 FLP control relays can be operated by an approved intrinsically safe controller (such as a MineWatch PC21) and Interface to FLP control circuits. The unit can also have up to two 12Vdc 500mA intrinsically safe outputs.
The PS21 (D) and PS21-B (D) units have 2 x 25mm threaded FLP cable gland entries. The PS21-R (D) and PS21-Int/R units have 6 x 25mm threaded FLP cable gland entries.
MineWatch PS21 variants: when mounted directly to a MineWatch PC21 controller, a through adaptor plate is fitted instead of the intrinsically safe terminal chamber to accommodate the through connection of the 12vdc supply and control relays.
The Davis Derby PS21 Range is certified Flameproof and Intrinsically Safe to the European ATEX standard for Group I atmosphere (methane in underground coalmines).
Certificate Number: Baseefa 07ATEX0161
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I M2 (M1) Ex d [ia Ma] I Mb-PS21 Power Supply fitted with Battery
The Davis Derby PS21 Range is also certified Flameproof and Intrinsically Safe to the IEC standard for Group I atmosphere (methane in underground coalmines).
Certificate Number: IECEx BAS 09.0051
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