We are in the process of designing a wall mount terminal that mounts on a docking station. It uses a 2 wire class 2 supply. My question has to do with the DC to AC inverter that is used to power the LCD. The input power is 5 Vdc @ .7 Adc, the output voltage is 1100 Vrms @ 5.4 marms and the operating frequency is 32 to 42 KHz. My question is since this has high series internal impedance it is responsible for a constant current. because of this the circuit produces its nominal output current under almost any load, from high impedance to a dead short. Since this output is an "ac constant current source" the output will supply its nominal output current into a shout circuit. This circuit satisfies the definition of "Limited Current Circuits" in 1950 .In a single fault condition the current measured is 6.6 ma @33KHz under the 23.8 ma allowable at this frequency.
None of this is operator accessible with power on. My questions are; Is reinforced insulation required on the output section? Or because it falls under the Limited Current Circuits basic insulation is required. I don't know the rationale behind this section of the standard but it seems it is not exactly a safe circuit. Thanks in advance Bob McIntosh Kronos Inc
