Redundancy Page
The Redundancy page in the Calculation Properties window for a block specifies information about the redundancy of the block. For properties other than Quantity to be available, its value must be greater than 1. The following table describes the properties on the Redundancy page.
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Property
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Description
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Quantity
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The total number of units present in the system (online). The default is 1. For properties under Redundancy to be available, the quantity must be greater than 1.
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Redundancy
Properties under this heading are available only when the quantity specified above is greater than 1. The selection that you make for Redundancy Type determines what other properties in this area are made available.
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Redundancy Type
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The type of redundancy. Choices are Series, Parallel Operating, Standby, and Load-Sharing. When Series is selected, no redundancy exists. For descriptions of the other three choices, see Redundancy Types.
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Quantity Required
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The number of units required for operation. This field is available when the quantity is greater than 1 and the redundancy type is other than series (which has no redundancy). The default is 1. To indicate redundancy, the number of units required for operation must be less than the total number of units present in the system. For example, for a one-out-of-two (1::2) parallel redundancy, 2 is entered for Quantity and 1 is entered for Quantity Required.
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Switch Probability of Success
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A probability value between 0 and 1 that indicates whether the switch will be operable at the time the active unit fails and the backup unit is made fully active. The default is 1.
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Switch Delay Time
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The time required for the switch between the active unit and the backup unit. This property is available only when the redundancy type is Standby. The default is 0. In the field to the right, you specify the units for this value. The choices are Minutes or Seconds. The default is Minutes.
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Load sharing
The properties under this heading are available only if Load Sharing is selected for Redundancy Type. As described in Load-Sharing Redundancy, the failure of one component in a load-sharing relationship causes the other components to work harder, thereby changing their failure characteristics. The properties in this area are specific to the block. Interactions available for a load-sharing block are described in Load-Sharing Notes.
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Load
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The percentage of the load that the block is to carry. The default is 100.
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Load Life Relationship
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Indicates the load life model to use, along with the block’s underlying failure distribution, to evaluate the failure characteristics of the components remaining in operation when one of their fellow load-sharing components fails. When a load-sharing component fails, the remaining load-sharing components are required to assume its portion of the load. The load life model indicates how the additional stress affects the failure characteristics of the surviving load-sharing components. Choices are Arrhenius, Exponential, Eyring, and Power. The default is Power. For more information, see Load Life Models.
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Life stress parameter
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The value that the selected life-load model requires for the stress level. The default value is 1.
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Weight
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Indicates the relative weight of the component in the load-sharing relationship. This field is available only if you use a junction to indicate the load-sharing relationship. If all units share the load equally, they have equal weights. The default is 1. The minimum is 0.
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