AuCom MVE Series User Manual page 34

Motor thermal capacity
The motor thermal model permits the motor to operate safely within its available thermal capacity, with any
combination of hot or cold starts and allowing for cooling between starts.
Motor thermal capacity
100%
3
2
1
0%
1 Ambient temperature (0% thermal capacity)
2 Steady state temperature
3 Motor overload protection trip point
4 Motor temperature rise from cold start to full load (∆t
5 Thermal capacity available for hot start
6 Thermal capacity available for cold start
Motor heating
Motor heating cycle
100%
1
0%
1 Cold start
2 Running at FLC
3 Off
4 Warm start
5 Locked rotor time (cold)
6 Locked rotor time (warm)
7 Locked rotor time (hot)
8 Failed start - insufficient thermal capacity (refer to
Cold start
•
When a motor starts from ambient temperature, it can withstand a longer locked rotor time (cold locked rotor time).
The motor temperature rises while the motor is running until it reaches the steady state temperature.
Warm start
•
If another start occurs before the motor has cooled completely from the first operating cycle, the locked rotor time is
shorter (hot locked rotor time). The available thermal capacity for this start is less.
In this example, the second start is successful.
5
6
4
21355.A
5
3
2
Time
)
1
6 7
8
3
2
4
21409.A
Hot start
)
MVE User Manual (710-17074-00H) |
MOTOR PROTECTION
33