Automation Direct Stellar SR55 Series - Estimating Energy Savings

Page 4–6 Stellar
®
SR55 Series Soft Starter User Manual – 1st Ed, Rev F – 09/18/2019
Chapter 4: Principles of iERS (intelligent Energy Recovery System)
esTimaTing energy savings
Basis for estimations:
• 3-phase squirrel cage induction motor, standard type�
• Supply: 380 to 440V, 50Hz�
• Supply voltage > minimum working voltage on motor rating plate�
• Operation 30% rated nameplate full load�
Table 4.6.1: esTimaTions
Energy Savings Estimations – Table 4.6.1
Motor Size kW HP Estimated Savings (% rated kW)
Less than
5 7�5 10
22�5 30 6�5
55 75 3�5
110 150 2�5
More than 110 150 1�5
Table 4.6.2: modifying faCTors
Energy Savings Modifying Factors – Table 4.6.2
Motor Poles Motor Slip
Number of Poles Add (% kW) % Slip Add (% kW)
2 -0�5 0�5 -0�5
4 0 2 0
6 0�5 3�3 0�5
8 1 5 1
Examples of estimated energy savings:
1) 37.5 kW 4-pole motor
From Table 1, use the estimated savings figure for the next higher rating, i.e. 55 kW.
The savings would be approximately 3.5% x 37.5 kW = 1.3125 kW.
For the 30% loaded motor, the savings are 1.3125 kW / (30% x 37.5 kW) = 11.6% savings.
2) 37.5 kW 2-pole motor
From Table 1, use the estimated savings figure for the next higher rating, i.e. 55 kW.
From Table 2, apply the pole-number factor of -0.5 %.
The savings would be approximately (3.5 % - 0.5 %) x 37.5 kW = 1.125 kW.
For the 30% loaded motor, the savings are 1.125 kW / (30% x 37.5 kW) = 10% savings.
3) 37.5 kW 2-pole ‘low slip’ motor
From Table 1, use the estimated savings figure for the next higher rating, i.e. 55 kW.
From Table 2, apply the pole-number factor of -0.5 % and the %-slip factor of -0.5%.
The savings would be approximately (3.5 % - 0.5 % - 0.5 %) x 37.5 kW = 0.938 kW.
For the 30% loaded motor, the savings are 0.938 kW / (30% x 37.5 kW) = 8.3% savings.