3. make sure that the resistor can dissipate the energy transferred to it during the braking:
•
Braking energy is not greater than the resistor heat dissipation capacity (E
r
) during
the period specified. See the custom resistor specification.
• The resistor is installed in a correctly ventilated and cooled space. Otherwise the
resistor cannot meet its heat dissipation capacity and overheats.
4. make sure that the instantaneous load capacity of the custom resistor is greater than
the maximum power taken by the resistor when it is connected to the drive intermediate
DC circuit by the chopper:
where
Instantaneous load capacity of the custom resistor
P
R, inst
Drive intermediate DC circuit voltage.
1.35 · 1.2 · 415 V DC (when supply voltage is 380 to 415 V AC)
1.35 · 1.2 · 500 V DC (when supply voltage is 440 to 500 V AC) or
1.35 · 1.2 · 690 V DC (when supply voltage is 525 to 690 AC)
U
DC
Resistance of the custom resistor
R
Selecting and routing the cables of custom resistors
Cable type
Use the same cable type for the resistor cabling as for the drive input cabling or, alternatively,
a two conductor shielded cable with the same cross-sectional area.
Maximum cable length
The maximum length of the resistor cable(s) is 10 m (33 ft).
Minimizing electromagnetic interference
Obey these rules in order to minimize electromagnetic interference caused by the rapid
current changes in the resistor cables:
• Shield the braking power line completely, either by using shielded cable or a metallic
enclosure. Unshielded single-core cable can only be used if it is routed inside a cabinet
that efficiently suppresses the radiated emissions.
• Install the cables away from other cable routes.
• Avoid long parallel runs with other cables. The minimum parallel cabling separation
distance is 0.3 meters (1 ft).
• Cross the other cables at 90 degree angles.
• Keep the cable as short as possible in order to minimize the radiated emissions and
stress on chopper IGBTs. The longer the cable the greater the radiated emissions,
inductive load and voltage peaks over the IGBT semiconductors of the brake chopper.
Note: ABB has not verified that the EMC requirements are fulfilled with custom brake
resistors and cabling. The customer must consider the EMC compliance of the complete
installation.
Resistor braking 263
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