Motor Insulation; Motor Bearing Currents - Danfoss VLT Refrigeration Drive FC 103 Design Manual

System Integration
Basic standard
Acceptance criterion
Voltage range: 200–240 V, 380–500 V, 525–600 V, 525–690 V
3 3
Line
Motor
Control wires
Standard bus
Relay wires
Application and Fieldbus
options
LCP cable
External 24 V DC
Enclosure
Table 3.7 EMC Immunity Form
1) Injection on cable screen.
2) Values typically obtained by testing.

3.2.5 Motor Insulation

Modern motors for use with frequency converters have a
high degree of insulation to account for new generation
high-efficiency IGBTs with high dU/dt. For retrofit in old
motors, confirm the motor insulation or mitigate with
dU/dt filter or, if necessary, a sine-wave filter.
For motor cable lengths ≤ the maximum cable length
listed in chapter 7 Specifications, the motor insulation
ratings listed in Table 3.8 are recommended. If a motor has
lower insulation rating, use a dU/dt or sine-wave filter.
Nominal mains voltage [V]
≤420
U
N
420 V< U ≤ 500
N
500 V< U ≤ 600
N
600 V< U ≤ 690
N
Table 3.8 Motor Insulation
44
®
VLT Refrigeration Drive FC 103
2) 2)
Burst Surge
IEC 61000-4-42) IEC 61000-4-5
B B
2 kV/2 Ω DM
4 kV CM
4 kV/12 Ω CM
4 kV CM
4 kV/2 Ω
2 kV CM
2 kV/2 Ω
2 kV CM
2 kV/2 Ω
2 kV CM
2 kV/2 Ω
2 kV CM
2 kV/2 Ω
2 kV CM
2 kV/2 Ω
0.5 kV/2 Ω DM
2 V CM
1 kV/12 Ω CM
— —
Motor insulation [V]
Standard U =1300
LL
Reinforced U =1600
LL
Reinforced U =1800
LL
Reinforced U =2000
LL
Danfoss A/S © 08/2015 All rights reserved.
Radiated electromagnetic
2)
ESD
IEC
IEC 61000-4-3
61000-4-2
B
—
1) —
1) —
1) —
1) —
1) —
1) —
—
8 kV AD
6 kV CD

3.2.6 Motor Bearing Currents

To minimise bearing and shaft currents, ground the
following to the driven machine:
•
Frequency converter
•
Motor
•
Driven machine
Standard mitigation strategies
1. Use an insulated bearing.
2. Apply rigorous installation procedures:
2a Ensure that the motor and motor load
are aligned.
2b Strictly follow the EMC Installation
guideline.
2c Reinforce the PE so the high frequency
impedance is lower in the PE than the
input power leads.
2d Provide a good high-frequency
connection between the motor and the
frequency converter, for instance, by
screened cable which has a 360°
connection in the motor and the
frequency converter.
2e Make sure that the impedance from
frequency converter to building ground
is lower that the grounding impedance
RF common
field mode voltage
IEC 61000-4-6
A A
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
— 10 V
RMS
10 V/m —
MG16G202