Imbalanced loads - What members should consider
NECA Technical have been receiving calls relating to some quite obscure electrical situations, which members have been experiencing.
We have written the following article to assist our members in understanding why balanced loads are important.
An imbalanced load can be described as
With perfect conditions i.e. with only linear loads connected to the system, the phases of power supply are 120 degrees apart in terms of phase angle and magnitude of their peaks should be the same.
On a distribution level, any load imperfections cause
What does this mean?
Imbalance can decrease motor efficiency by causing extra heating in a motor. The heat generated can also affect a motors life by decomposing the grease or oil in the bearings and de-rate motors windings.
Uninterruptible power supplies (UPS) or inverter supplies also perform with poor efficiency and inject more harmonic currents.
Imbalances can cause the de-rating of power cables by increasing I2R losses (power loss caused by the flow of a current I through a resistance R) in the cable. For distribution
The causes of imbalance can be attributed to:
Three phase equipment such as an induction motor with
A large single phase load, or a number of small loads connected to only one phase, cause more current to flow from that particular phase causing
Methods to reduce imbalance include: