Specifications

2.10 Earth Leakage Current
WARNING
DISCHARGE TIME
Touching the electrical parts could be fatal - even after
the equipment has been disconnected from mains.
Also make sure that other voltage inputs have been
disconnected, such as load sharing (linkage of DC
intermediate circuit), as well as the motor connection for
kinetic back-up.
Before touching any electrical parts, wait at least the
amount of time indicated in the Table 2.1.
Shorter time is allowed only if indicated on the
nameplate for the specific unit.
NOTICE
Leakage Current
The earth leakage current from the frequency converter
exceeds 3.5 mA. To ensure that the earth cable has a
good mechanical connection to the earth connection, the
cable cross section must be at least 10 mm
2
Cu or 16
mm
2
Al or 2 rated earth wires terminated separately.
Residual Current Device protection RCD
This product can cause a DC current in the protective
conductor. Where a residual current device (RCD) is used
for protection in case of direct or indirect contact, only
an RCD of Type B is allowed on the supply side of this
product. Otherwise, another protective measure shall be
applied, such as separation from the environment by
double or reinforced insulation, or isolation from the
supply system by a transformer. See also Application
Note Protection against Electrical Hazards, MN90G.
Protective earthing of the frequency converter and the
use of RCDs must always follow national and local
regulations.
2.11 Extreme Running Conditions
Short circuit (motor phase – phase)
Current measurement in each of the 3 motor phases or in
the DC-link, protects the frequency converter against short
circuts. A short circuit between 2 output phases causes an
overcurrent in the inverter. The inverter is turned off
individually when the short circuit current exceeds the
permitted value (Alarm 16 Trip Lock).
To protect the frequency converter against a short circuit
at the load sharing and brake outputs see the design
guidelines.
Switching on the output
Switching on the output between the motor and the
frequency converter is fully permitted. The frequency
converter is not damaged in any way by switching on the
output. However, fault messages may appear.
Motor-generated over-voltage
The voltage in the intermediate circuit is increased when
the motor acts as a generator. This occurs in following
cases:
1. The load drives the motor (at constant output
frequency from the frequency converter), that is
the load generates energy.
2. During deceleration ("ramp-down") if the moment
of inertia is high, the friction is low and the ramp-
down time is too short for the energy to be
dissipated as a loss in the frequency converter,
the motor and the installation.
3.
Incorrect slip compensation setting (1-62 Slip
Compensation) may cause higher DC link voltage.
The control unit may attempt to correct the ramp if
possible (2-17 Over-voltage Control.)
The inverter turns off to protect the transistors and the
intermediate circuit capacitors when a certain voltage level
is reached.
Mains drop-out
During a mains drop-out, the frequency converter keeps
running until the intermediate circuit voltage drops below
the minimum stop level, which is typically 15% below the
frequency converter's lowest rated supply voltage. The
mains voltage before the drop-out and the motor load
determines how long it takes for the inverter to coast.
2.11.1
Motor Thermal Protection
This is the way Danfoss protects the motor from being
overheated. It is an electronic feature that simulates a
bimetal relay based on internal measurements. The charac-
teristic is shown in Illustration 2.27.
1.21.0 1.4
30
10
20
100
60
40
50
1.81.6 2.0
2000
500
200
400
300
1000
600
t [s]
175ZA052.12
f
OUT
= 2 x f
M,N
f
OUT
= 0.2 x f
M,N
f
OUT
= 1 x f
M,N
(par. 1-23)
I
MN
(par. 1-24)
I
M
Illustration 2.27 Motor Thermal Protection Characteristic
The X-axis is showing the ratio between I
motor
and I
motor
nominal. The Y-axis is showing the time in seconds before
Product Overview
VLT
®
HVAC Basic Drive FC 101 Design Guide
38 MG18C502 - Rev. 2013-09-06
22