Installation / Operation / Maintenance Manual
10/28/2019
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because the dropout point would have to be set so high it would cause nuisance undervoltage indications.
Figure 4
Figure 5
The vertical line in Figures 4 and 5 indicates the protection undervoltage relays provide against voltage unbalance when it is
calibrated for an 87% drop out. The Lake Shore Voltage Sensing Relay will drop-out on a 4% voltage unbalance, thus limiting the
motor overheating to 32% above normal. A line to line type voltage sensing relay with the same dropout point will not dropout until
the system has an 8.5% voltage unbalance, thus allowing a 140% above normal temperature rise on any motors connected to this
system.
