Trane Starters Engineering Bulletin page 16

Motor Protection
Phase failure/loss protection
The chiller will shut down if any of the three-phases of current feeding the motor drop below
10 percent RLA for 2.5 seconds.
Phase imbalance protection
Based on an average of the three phases of current, the ultimate phase-imbalance trip point is
30 percent.The RLA of the motor can be derated depending on the percent of this imbalance.The
phase-imbalance trip point varies based on the motor load.
Phase reversal protection
Detects reverse-phase rotation and shuts the chiller down (backwards rotation).
Under/overvoltage protection
The chiller is shut down with an automatic reset due to excessive line voltage ±10 percent of the
design voltage.
Short cycling protection
Prevents excessive wear on the motor and starter due to heating from successive starts.The unit
controller uses an algorithm based on a motor heating constant and a background timer
(measuring the running time since the last start).
Supplemental motor protection
This is a set of optional motor protection features, offered as a option in addition to the Enhanced
Electrical Protection Package (see
(Enhanced Electrical Protection Package option), " p.
16
"SMP , Supplemental Motor Protection—Medium voltage only
66).
CTV-PRB004-EN