Brake Cable; Motor Insulation; Motor Bearing Currents - Danfoss VLT AQUA Drive FC 202 Installation Manual

Electrical Installation
Motor
U
2
U
1
4 4
FC
96
Motor
U
2
U
1
FC
96
Figure 4.3 Motor Rotation Check
F-frame requirements
Use motor phase cables in quantities of 2, resulting in 2, 4,
6, or 8 to obtain an equal number of wires on both
inverter module terminals. The cables are required to be
equal length within 10% between the inverter module
terminals and the first common point of a phase. The
recommended common point is the motor terminals.
Output junction box requirements
The length, a minimum of 8 ft [2.5 m], and quantity of
cables must be equal from each inverter module to the
common terminal in the junction box.
NOTICE!
If a retrofit application requires an unequal number of
wires per phase, consult the factory or use the top/
bottom entry side cabinet option, instruction 177R0097.

4.6.2 Brake Cable

Adjustable frequency drives with factory installed brake
chopper option
(Only standard with letter B in position 18 of type code).
The connection cable to the brake resistor must be
shielded and the max. length from adjustable frequency
drive to the DC bar is limited to 82 ft [25 m].
38
VLT
V W
2 2
V W
1 1
97 98
V W
2 2
V W
1 1
97 98
Danfoss A/S © 10/2015 All rights reserved.
®
AQUA Drive FC 202 Low Harmonic Drive
Terminal No.
81, 82
Table 4.3 Terminal Functions
The connection cable to the brake resistor must be
shielded. Connect the shield with cable clamps to the
conductive backplate of the adjustable frequency drive
and the metal cabinet of the brake resistor.
Size the brake cable cross-section to match the brake
torque. See also Brake Instructions for further information
regarding safe installation.
WARNING
Note that voltages up to 790 V DC, depending on the
supply voltage, are possible on the terminals.
F-frame requirements
The brake resistors must be connected to the brake
terminals in each inverter module.

4.6.3 Motor Insulation

For motor cable lengths ≤ the maximum cable length, the
motor insulation ratings listed in Table 4.4 are
recommended. The peak voltage can be twice the DC link
voltage or 2.8 times AC line voltage, due to transmission
line effects in the motor cable. If a motor has lower
insulation rating, use a dU/dt or sine-wave filter.
Nominal AC Line Voltage
≤ 420 V
U
N
420 V < U ≤ 500 V
N
Table 4.4 Recommended Motor Insulation Ratings

4.6.4 Motor Bearing Currents

Motors with a rating 110 kW or higher combined with
adjustable frequency drives are best with NDE (Non-Drive
End) insulated bearings to eliminate circulating bearing
currents caused by motor size. To minimize DE (Drive End)
bearing and shaft currents, proper grounding is required
for:
•
Adjustable frequency drive
•
Motor
•
Motor-driven machine
•
Motor to the driven machine
Although failure due to bearing currents is infrequent, use
the following strategies to reduce the likelihood:
Function
Brake resistor terminals
Motor Insulation
Standard U = 1,300 V
LL
Reinforced U = 1,600 V
LL
MG21B322