Specifications

Protections Ver: 0002 E - 5
Calculating the I
2
t implies an ambient temperature of 40°C (104°F). For temperatures of up to
55°C (131°F) (the maximum allowed) and since the driver does not know the actual ambient
temperature, this protection may not be sufficient. In this case and if the operator would use a
cycle which would exceed the derating, it could damage the drive.
As soon as it is possible to vary the frequency of the PWM, the maximum limit of the I
2
t
allowed it will adapt automatically in order to consider the losses in the commutations
corresponding to each frequency.
Equivalent duty cycles.
These drives will also admit any other equivalent duty cycle whose rms current is the one
permitted in its derating graph.
The graph below shows an example of two equivalent duty cycles. The integral of the I
2
t is the
same in both cases even when the integral of the It product is greater in the first case (a).
Time
Current
a
b
In
Ip
T T