Calculate electrical energy consumption and demand using VFD speed and motor size (affinity law)
Objective/Method/Outcome
- Objective: Calculate energy consumption and demand for a variable speed motor using their speed command/feedback and the motor size.
- Method: This rule is using the pump/fan affinity law.
- Outcome: Energy consumption and demand are calculated and output as CTLs
Logic
- Motor size, efficiency, and VFD speed are all input
- Motor size is converted from hp to kW
- Efficiency is converted from a percentage to a decimal
- VFD speed is factored by a Power Consumption Factor(VFD speed/100)^3
- The demand is calculated by multiplying the above resultant value with the motor size, divided by the efficiency
- Consumption is calculated by multiplying demand by 5/60 (5 minutes/60 minutes) to get kWh
- Consumption is summed hourly
- Hourly Electrical Energy Consumption, Demand (5-minute resolution), and a Virtual Meter CTL are output
Description / Method
Calculate energy consumption and demand for a variable speed motor using their speed command/feedback and the motor size. This rule is using the pump/fan affinity law.
Diagnosis / Recommended Action
N/A
Message
This Rule does not trigger an Insight.
Notes
FOR THIS RULE TO BE VALID YOU MUST EDIT THE INPUT BLOCK “MOTOR SIZE [hp]” TO MATCH ACTUAL PUMP/FAN SIZE.
This rule is using the pump/fan affinity law. P1 / P2 = (n1 / n2)^3
n1 is the speed command/feedback n2 is 100% speed P1 is the power consumption at speed n1 (CTL) P2 is the motor size (name-plate rating)
Default Constants:
- Const. – Efficiency [%]: 95
CTL Generated:
- Virtual Meter – Accumulating Energy [kWh]
- Hourly Electrical Energy [kWh]
- Electrical Demand [kW]
Rule Template Type
- Insight Type: N/A – No Insight triggered
- Trigger Type: Active High
Default Priority
N/A – no Insight triggered
Inputs
| Inputs | Units | Default Value | Tags | Description |
|---|---|---|---|---|
| Motor Size | hp | sensor, leaving, hot, water, temp | Motor size in horse power | |
| Efficiency | % | 95 | sp, leaving, hot, water, temp | Motor Efficiency |
| Speed (VFD) | % | cmd|feedback|status, speed | VFD speed trend |
Output Calculated Trend Logs
| Output CTL | Units | Description |
|---|---|---|
| Virtual Meter – Accumulating Energy | kWh | Virtual meter (Accumulating CTL) of motor energy consumption |
| Hourly Electrical Energy | kWh | Non-accumulating CTL of hour to hour electrical consumption |
| Electrical Demand | kW | Electrical demand CTL with 5-minute resolution |