Open-load, over-current, over-voltage and over-temperature fault conditions are detected by the diagnostic output module.
When an output fault is detected In the B882 mode, the module without controller intervention disarms the faulted output and reports the condition to the controller via discrete input (1x), or input register (3x) points. The point remains disarmed until the user’s logic rearms the point by turning the point back on. To turn the point back on the user’s logic must turn the point first off and then on.
NOTE: If the controller attempts to turn a faulted point back on, there must be a 2 -5 s delay from the time of a fault to the time of cycling the faulted point on. When this delay is not given, the module ignores the change. When the fault point is brought low, the fault indicator clears in the 2-5 s range.
NOTE: If field power is lost, the module may detect faults. After field power is reapplied, all faults must be cleared
NOTE: Clearing faults prior to restarting
When a fault is detected in either the B882 or B818 mode, the source of the fault should be cleared prior to restarting the point. Failing to clear the source of a fault may result in damage to the
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power source
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driven field-side device
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module
When an output fault is detected In the B818 mode, the module without controller intervention disarms the faulted output. Faults are not reported to the controller. To turn the point back on, the user’s logic must first turn the point off and then on.
NOTE: If the controller attempts to turn a faulted point back on, there must be a 2 - 5 s delay from the time of a fault to the time of cycling the faulted point on. When this delay is not given, the module ignores the change. When the faulted point is brought low, the fault indicator clears in the 2 -5 s range.
NOTE: Loss of power.
If field power is lost in the B818 mode, the module may detect faults that are not visible to the controller.
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Term
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Definition
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Open Load
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When the load current is less than, or equal to 100 mA, the output is turned OFF and the fault flag is set. To prevent the fault flag from being set, a resistor should be placed between the output point and the group return. For example, @ 20 Vdc the minimum load is 200 Ω, @ 24Vdc the minimum load is 240 Ω, and @ 28 Vdc the minimum load is 280 Ω. When the output is already on and the load exceeds the open load trip level for one to one and a half ms, the output is turned OFF, and the fault flag is set.
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Over Current
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When the load current exceeds the over current trip level following the switching of a point from OFF to ON, the output is turned OFF, and the fault flag is set. When the output is already on and the current exceeds the over current trip level for one to one and a half ms, the output is turned OFF, and the fault flag is set.
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NOTE: The over current trip level has a value of 3.5 A or greater. Over current greater than 12 A may cause point failure
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Term
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Definition
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Over Voltage
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If the external voltage supply exceeds the module’s rating, the output point turns OFF, and a fault flag may be returned. The point requires cycling after the external supply returns to a safe operating level. The over-voltage trip level has a value greater than 31 Vdc. There is no time delay.
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Over Temperature
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When the junction temperature of the output transistor reaches 140°C or greater, the output is turned OFF, and the fault flag is set.
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NOTE: the following about unused outputs in a B882
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Unused outputs should not be turned on since their field points are not wired.
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Turning them on will cause an open load fault and the active light will blink.
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The minimum load required is 100 mA.
