Danfoss VLT Refrigeration Drive FC 103 Operating Instructions Manual page 56

Electrical Installation
alarm relay for external use is associated with each
setpoint.
NOTICE
Only 1 insulation resistance monitor can be connected to
each ungrounded (IT) system.
•
Integrated into the frequency converter Safe
Torque Off circuit.
4 4
•
LCD display of the ohmic value of the insulation
resistance.
•
Fault memory.
•
INFO, TEST, and RESET keys.
IEC emergency stop with Pilz safety relay
Includes a redundant 4-wire emergency-stop push button
mounted on the front of the enclosure and a Pilz relay that
monitors it in conjunction with the frequency converter
STO (Safe Torque Off) circuit and the mains contactor
located in the options cabinet.
Manual motor starters
Provide 3-phase power for electric blowers often required
for larger motors. Power for the starters is provided from
the load side of any supplied contactor, circuit breaker, or
disconnect switch. Power is fused before each motor
starter, and is off when the incoming power to the
frequency converters is off. Up to 2 starters are allowed (1
if a 30 A, fuse-protected circuit is ordered), and are
integrated into the frequency converter STO circuit.
Unit features include:
•
Operation switch (on/off).
•
Short-circuit and overload protection with test
function.
•
Manual reset function.
30 A, fuse-protected terminals
•
3-phase power matching incoming mains voltage
for powering auxiliary customer equipment.
•
Not available if 2 manual motor starters are
selected.
•
Terminals are off when the incoming power to
the frequency converter is off.
•
Power for the fused protected terminals is
provided from the load side of any supplied
contactor, circuit breaker, or disconnect switch.
In applications where the motor is used as a brake, energy
is generated in the motor and sent back into the
frequency converter. If the energy cannot be transported
back to the motor, it increases the voltage in the frequency
converter DC line. In applications with frequent braking
and/or high inertia loads, this increase may lead to an
overvoltage trip in the frequency converter and finally a
shut down. Brake resistors are used to dissipate the excess
energy resulting from the regenerative braking. The resistor
is selected based on its ohmic value, its power dissipation
52
®
VLT Refrigeration Drive FC 103 Low Harmonic Drive
rate, and its physical size. Danfoss offers a wide variety of
different resistors that are specifically designed for Danfoss
frequency converters.
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