Nidec Unidrive M600 Series - 4.5 Cable lengths

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Unidrive M Regen Design Guide 67
Issue Number: 4
4.5 Cable lengths
Since capacitance in the cabling causes loading, the Regen/motoring system cable length should not exceed the values given in Table 4-11 to
Table 4-14 Regen system maximum cable lengths, without the addition of extra components.
To determine cable length, the Regen/motoring system should be considered as a number of sections as detailed in Figure 4-14 and the description
below.
Figure 4-14 Unidrive M Regen system cables
Cable length A is the Vac cable situated between the Regen inductor and the Regen drives power terminals, U, V and W. In general no special
precautions are necessary for the AC supply wiring to the Regen drive however it should be noted the high frequency PWM is present here.
Ideally the Regen inductor should be mounted close to the Regen drive terminals. If a cable length longer than 5 m is used, a shielded cable with the
grounded shield should be used. Where the Regen inductor is situated close to the Regen drive, Cable length A need not be considered when
calculating the total cable length.
Cable length B is the length of the DC bus connection between the Regen drive and motoring drive(s). The common +/- DC bus connections
between all drives should be treated as a single two core cable when calculating the length, and not two individual cables lengths. The DC power
output from the Unidrive M Regen drive which is used as the input stage to the Motoring drive(s) carries a common-mode high frequency voltage
comparable with the output voltage from a standard drive. All precautions recommended for motor cables must also be applied to all cables
connected to this DC circuit, cable length, shield, grounding and segregation.
Cable length C (C1 and C2) is the total AC cable length between all Motoring drive(s) and their motors. Figure 4-14 shows a Regen system and the
cable connections A, B and C1 + C2.
Therefore the cable length for the Regen system will be, Total cable length = Cable length B + Cable length C1 + Cable length C2.
The total system cable length for the Regen system should be compared with the maximum cable length listed for the Regen drive in Table 4-11 to
Table 4-14, if the total system cable length exceeds this value additional measures will be required, refer to section 4.6 Exceeding maximum cable
length on page 70.
Unidrive M
Regen Drive
Unidrive M
Motor drive number 1
.
Cable
length A
Cable length B
Cable
length C1
Unidrive M
Motor drive number 2
.
Cable
length C2
VAC power
supply
Motor No .1 Motor No .2
Regen
inductor