Siemens Midimaster Eco - D-R; De-Rating Information; Maximum Motor Cable Lengths; Thermal Protection and Automatic De-Rating

ECO REFERENCE MANUAL
14-1
D-R
14. DE-RATING INFORMATION
THERMAL PROTECTION AND
AUTOMATIC DE-RATING
Losses within the power module rise with
increasing switching frequencies, leading to
higher heatsink temperatures. If the inverter
operates outside its recommended ambient
operating temperature it would normally trip, with
an over-temperature fault code. To avoid such
nuisance tripping, the MICROMASTER
Eco/MIDIMASTER Eco automatically reduces it’s
switching frequency ( e.g. from 16kHz to 8kHz).
This reduces the temperature of the heatsink,
enabling the application to continue running - trip
free. Should the load or ambient temperature
then reduce, the inverter will first check to see if it
is safe to increase the switching frequency again
and then do so.
See parameter P076 for a list of de-ratings
applicable to particular ratings.
MAXIMUM MOTOR CABLE LENGTHS
The tables shown below give an indication of the
maximum motor cable allowed to be connected to
the inverter without the use of additional output
chokes.
I is the motor current and I
N
is the nominal motor
current (P083). Many application do not require
150% overload i.e. I/I
N
= 1.5, therefore this ratio
may be reduced using P186 (instantaneous
current limit) offering the added benefit of driving
longer cable lengths.
Standard MICROMASTER Eco
units have a maximum value of
I/I
N
= 1.5 (i.e. 150% overload).
For cable lengths greater than those specified in
the tables, an external output choke is required,
see section 15.
Maximum cable lengths and derating with respect to load current
208/240V MICROMASTER Eco:
Un-screened cable
F
max
= 16kHz (Switching Frequency)
Current (I/I
N
) ECO1-75/2 ECO1-110/2 ECO1-150/2 ECO1-220/2 ECO1-300/2 ECO1-400/2
Cable length (m)
1.5 200 200 200 185 185 185
1.4 200 200 200 200 200 200
1.3 200 200 200 200 200 200
1.2 200 200 200 200 200 200
1.1 200 200 200 200 200 200
1.0 200 200 200 200 200 200