Chapter 6 – Parameters
ACH 500 Programming Manual
6-33
4 MOTOR THERM TIME
The time period within which the motor temperature reaches 63 percent of the
final temperature rise. As a rule of thumb, Motor Thermal Time equals 35
times t6 (t6 in seconds is the time that the motor can safely operate at six
times its rated current, given by the motor manufacturer). Table 6-16 shows
some motor thermal times measured by ABB. The default value is set to 700s,
which is the value for a Class 20 trip curve. This has been tested and is UL
Listed as motor overload protection. The time for a Class 10 trip curve is 350s
and for a Class 30 trip curve is 1050s.
Table 6-16 Motor Thermal Times
P
N
[HP]
Number of Poles
2
4
6
t
[s]
t
[s]
t
[s]
3
660
1020
1440
5
780
1140
1740
7.5
900
1260
1760
10
970
1380
1860
15
1140
1560
2040
20
1200
1740
2340
25
1260
1860
2340
30
1380
2040
2760
40
1680
2220
2940
50
1860
2460
3180
60
2040
2640
3420
75
2220
2820
3660
100
2400
3120
3960
125
2640
3300
4320
150
2820
3600
4680
200
3120
3960
5100
250
3420
4320
5700
300
3780
4740
6420
350
3780
4740
6420
400
3780
4740
6420