Output Reactors (Chokes) - Siemens Midimaster Eco Reference Manual

OUTPUT REACTORS (CHOKES)

Output reactors are fitted to the output terminals (U, V & W) of the inverter to allow operation with long
motor cables. The inductance of the output reactor compensates for the stay phase-to-phase and
phase-to-earth capacitance of the motor cable.
As the motor cable length is increased the total stray capacitance of the motor cable also increases.
This stray cable capacitance combined with the residual voltage spikes on the inverter output (caused
by the Pulse Wide Modulation (PWM) switching of the inverter's IGBT output devices) has the effect of
causing current spikes to flow back to the inverter. These current spikes may cause nuisance tripping
of the inverter which can be prevented by the installation of an output reactor.
The recommended motor cable lengths for screened and unscreened cables when output reactors are
fitted are shown within the table below:
Maximum Cable Length (m)
for MICROMASTER Eco & MIDIMASTER Eco
Inverter Standard (no output
Rating reactor fitted)
(kW)
Screened
Cable
Up to 1.5kW 80
2.2 to 3 135
4 200
5.5 200
7.5 200
11* 50
15* 50
18.5* 50
22* 50
30* 50
37* 50
45* 50
55 300
75 300
90 200
15-28
Output Reactor
Unscreened Screened Cable
Cable
One
Reactor
Fitted
110 150
165 200
200 250
200 250
200 250
50 100
50 100
50 100
50 100
50 100
50 100
50 100
300 300
300 300
300 300
ECO REFERENCE MANUAL
Output Reactor
Fitted
Unscreened Cable
Two Reactors One
Fitted in Reactor
Series Fitted
200 180
250 250
300 300
300 300
300 300
150 150
150 150
150 150
150 150
150 150
150 150
150 150
400 400
400 400
400 400
Fitted
Two
Reactors
Fitted in
Series
250
300
350
350
350
200
200
200
200
200
200
200
500
500
500