*
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-
2192
72
29
Carrier Frequency Derating
When a transistor turns on or off, there is a transition time between the fully off state and the fully on state
and vice versa. During this transition time, there is effective resistance and subsequent heating in the
transistor. This heating effect is a function of current squared times time (I
2
t). For a fixed amount of
current, the longer the transition time, the more heating that will occur inside the transistor. In addition,
the more times that the transistor turns on or off within a period of time, the more heating that will occur.
This means that the higher the carrier frequency, the more the heating in the drive and consequently, the
lower the full load current value will be.
The following software limit curve applies to all G3’s 100HP and smaller
:
Carrier Frequency Derate 100HP & Smaller
0
0.2
0.4
0.6
0.8
1
1.2
0
1
2
3
4
5
6
7
8
9
10
11
12
Carrier Frequency
Derate Multiplier
