4.3.8.1. Power model and metrics
IRM can be used to model physical power-related connectivity and power usage much like it can model physical data connectivity, using the same objects: Equipment, Cables, Ports, and Plugs.
In IRM's power model, each Equipment can receive power over one Port and distribute it over multiple other Ports. The Equipment itself uses a specified amount of power during operation (the Equipment Type's Running Watts), and a potentially different amount of power during startup (Startup Watts). In other words, the total amount of power taken in by the device is equal to its own consumption plus all the power it distributes over its Ports.
An individual Port may either receive power or send it along to another Equipment object; in the former case the Power Flow property of its Port Definition is set to In, while in the latter case it's set to Out. Each Port has a rated voltage, which is given in the Connector Type and can be overridden in the Port Definition. Each Port also has a limit of how much current can flow through it, which is given by the Amps property of the Port Definition, subject to the rated maximum given in the Connector Type. Normally, the limiting factor is the value in the Port Definition which consider the electronics behind the Port; the Connector Type values are simply nominal maximum ratings for that type of connector and are often higher than what an actual Port can provide.
All power values are in watts or KVA, current is in amps, and electrical potential is in volts.
Basic Modeling Examples
Example 1: 6 way power strip
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It has one Port Definition with
Power Flow set to
In representing the Line side of the power circuit.
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It has 6 Port Definitions with
Power Flow set to
Out to represent the Load side of the power circuit.
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The strip itself consumes no power so the value of both Equipment Type's
Startup Watts and
Running Watts are 0 or small (< 1 watt).
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The value for Equipment's
Nominal total watts is equal to the sum of the
Nominal total watts values for all Equipment plugged into the power strip’s
Out ports.
Example 2: UPS
An uninterruptible power supply (UPS) is modeled similarly to a power strip, but uses more power itself, so is defined as follows:
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It has a Port Definition for each power line coming into the UPS from the power source, each port is defined as
Power Flow = In -
Its has a Port Definition for each power load connection feeding a powerstrip or directly connected Equipment, each port is defined as
Power Flow = Out -
As a UPS is an electronic device it consumes power so its associated Equipment Type
Startup Watts and
Running Watts are used to show how much power it consumes.
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Also, a UPS likely has at least two different types of ports (battery-backed vs. surge-protected) that have different ratings. Those Port Definitions use the same Jack Definition, but have different values for their Port Definition
Amps property values.
IRM's power metrics can be broken down into supply-side metrics and demand-side metrics. The following subsections examine each of these in turn.
Supply-side Power Metrics
The following Power Fields defined in the Equpment Type are used to specify the power Capacity of any given Equipment Type and is used to set the maximum power capacity of a power circuit:
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Power Capacity (for power distribution equipment e.g. Powerstrips, Power Outlets, PDU's, RPP's, Breakers, etc)
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Max power (W) can supply (used to set the maximum power that is supplied)
Power Capacity is used to describe the limit of how much total power a type of equipment can provide in the common cases where the individual Port ratings are not the limiting factor.
For example:
An uninterruptable power supply (UPS) is very likely to have a rating for how much power it can supply in total, which is substantially less than the amount that can be supplied over all of its power output Ports considering only the ratings on those Ports. In fact, for some smaller UPS's, the rating on the device is exactly the same as the rating on a single Port, so that the device can supply all of its power over a single Port.
Max power (W) can supply is an instance-level property, similar to Power Capacity, that can be applied to:
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to Equipment that is not an actual source of power e.g Powerstrip, but from which upstream power is not modeled in IRM and allows the organization to manage their power at different levels such as :
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Racks and cabinets have a Max Power (W) capacity of rack field that indicates how much total power the rack/cabinet can supply. Racks/cabinets also support a Max. power (W) inflow of rack that is the sum of the rated values of all Ports used to bring power into the rack, but as discussed previously, the Port ratings rarely provide the practical limit.
IMPORTANT: Objects within a Rack considered to be a source of power, influence the rack's Power Capacity. This enables users to start and end their power management all within a single Rack. In these cases, power strips or PDUs can be used as generators, by setting value for the maximum Supply Watts Declared property for the power strips/PDUs.
Max Free Power indicates how much power headroom is left after Nominal power (W) used in rack (or Measured power (W) used in rack, if that is available) and the Rack's Watts Flowing Out Designed (or Watts Flowing Out Measured if that is available) are both subtracted from the Rack's power capacity.
In other words, Max Free Power indicates the amount of capacity left over after the Rack consumes whatever it needs itself and supplies whatever power its “clients” use. In the case of a remote power panel, the amount of power consumed by the panel itself will be negligible, so this value will just depend on what it is supplying to the other Racks in the room.
Demand-side Power Metrics
As mentioned ealier, each Equipment Type has a Running Watts field that indicates how many watts the equipment itself uses. However, some Equipment objects are used to power other Equipment objects via Cables or via Slots, which results in a total amount of power consumed by the object and everything it powers -- that is Nominal total watts, or Measured total watts, if available.
In racks/cabinets, the Running Watts values for all contained equipment is aggregated into Nominal power (W) used in rack or Measured power (W) used in rack, if availble. Each rack/cabinet can be given a Power Factor and using that, IRM computes Nominal power (VA) used in rack (or Measured power (VA) used in rack). IRM also computes Total heat produced by rack from the appropriate total watts value.
