T1689 Technical Manual Rev 07
Drive (CDM) Design
MV3000 Air Cooled DELTA
Component Selection – Electrical
Page 95
3.8.3
Filters
3.8.3.1
PWM Filter
This must be fitted to an AEM drive to filter the PWM harmonics.
•
Sized for the application, depends on:
•
PWM frequency;
•
Supply reactance;
•
Impedance of the input reactor;
•
Drive rating;
•
Attenuation required (acceptable level of harmonics).
Due to the large variation of applications, standard versions are unavailable.
Electrical location shown in Section 11.5 - AEM Network Bridge: Power Connections.
3.8.3.2
EMC Filters
Used as part of the measures to attenuate the high frequency (radio frequency) emissions from the CDM.
•
Fitted to the a.c. supply connections to the CDM.
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Most effective when used at an EMC shielding boundary.
•
Cables and components (e.g. isolator) on the mains side of the filter must be screened
from the rest of the DELTA circuit.
•
Sized for the application.
•
Type and attenuation depend on the emission level required for application (see Section
3.3.1.4: Electrical Interference / Electromagnetic Compatibility (EMC)).
•
AEM style drives require more attenuation DFE drives.
•
Current rating based on the power rating of the CDM for the main supply connections, and
the power rating of auxiliary components for control supplies.
NOTE:
Auxiliary supplies may have lower emissions limits (see Section 3.3.1.4: Electrical Interference /
Electromagnetic Compatibility (EMC)).
•
EMC filters may only be used if the supply neutral is connected to earth/ground at the source of
the supply (also known as TN or TT network). They must not be used on networks with
ungrounded neutral (also known as IT network).
•
If EMC filters are to be used and there are also thyristor converters (e.g. d.c. drives) on the same
supply, there will be restrictions on the allowed commutation notch depth.
•
When used on AEM drives, filters must be rated for the voltage-to-ground.
3.8.4
Power Cabling & Terminals
Voltage Rating
The insulation between live conductors and between live conductors and ground (earth) must be suitable for
the voltages applied. In some locations there will be additional voltages due to PWM switching edges. These
edges may be amplified by ‘ringing’ caused by reflections or resonant circuits. Every layout will have different
stray inductive/capacitive circuits so the actual value must be measured.
Cable insulation must be selected to include a margin for these repetitive voltages.
Nominal (continuous) voltage ratings:
AEM drives, d.c. link voltage is usually 1.6x a.c. r.m.s. voltage.
DFE drive d.c. link voltage is 1.35x a.c. r.m.s. voltage.
