The Low Power Output Isolation module is designed to isolate Vital MICROLOK II Outputs and deliver an isolated DC voltage. The isolation withstanding voltage from output to output is 2000 V rms. Typically into a 200 to 400 ½ load operating from a MICROLOK II system supply of 12 VDC, the output is nominally 12 VDC.
The Low Power Output Isolation Module is housed in a plastic case that snaps on to a DIN rail for ease of mounting. The unit is 0.885" wide, 3.897" high and 4.507" deep. Four connectors are provided to facilitate wiring and they are keyed to prevent mis-wiring should a unit need replacement. It is designed to convert MICROLOK II vital outputs that are non-isolated into a replicated isolated output.
There are two variations of the isolation module. It is available in a configuration with two identical circuits that convert MICROLOK II vital non-isolated outputs to isolated outputs. It is also available with a single bi-polar isolated output. LEDs on the front of the unit provide excellent status information: a blinking LED indicates it is responding to MICROLOK II check pulses and proves the circuit is functional because the LED responds to the output voltage. When an LED is illumi-nated steady, it indicates an output is being delivered. In the bi-polar version, blinking LEDs have the same meaning and each of the steady indications designates a specific polarity of the output.
For each input to this device, two internal diodes are provided so that the isolation module is responsive to redundant MICROLOK II units. Particular attention was given in creating a unit for which a common mode failure would not escalate, causing each of the redun-dant MICROLOK II units to fail. For example, a shorted diode will cause the corresponding MICROLOK II unit to reset because it receives conflicting check pulses from the other MICROLOK II unit but the other unit will continue with uninterrupted service. A shorted output or other internal circuit failure will eliminate the cor-responding function to respond but both MICROLOK II units will continue with normal function.
For applications requiring more conservative redundan-cy, isolation module outputs can be wired in parallel. Elimination of any common galvanic connection point is one part of a general philosophy of total isolation between MICROLOK II units to preclude the possibil-ity that a surge or lightning strike that could affect both units simultaneously.
In either embodiment of the "OR" function, (diode ORing or cross wired outputs) the isolation module is ideally suited as a MICROLOK II accessory directed at providing uninterrupted service. It is particularly use-ful in implementation of seamless transfer of control or truly hot stand-by operation.
In common usage the isolation module provides the security inherent with double break circuits to operate relays or MICROLOK II inputs in remote cases. Surge protection to a level of 30 joules is built in, but external line to line and line to ground arrestors are recommend-ed for additional protection.
Currently units are available to convert 12 volt MICROLOK II outputs to a nominal 12 or 15 volts. Other voltage, outputs either greater than or less than the MICROLOK II output can be provided if needed.
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