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.

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