Parallel Connection Of Motors; Motor Thermal Protection; Voltage/Current Input Selection (Switches) - Danfoss VLT FC 102 Operating Instructions Manual

Electrical Installation

4.9.3 Parallel Connection of Motors

The frequency converter can control several parallel-
connected motors. The total current consumption of the
motors must not exceed the rated output current I
the frequency converter.
NOTICE
Installations with cables connected in a common joint as
in Illustration 4.15 are only recommended for short cable
lengths.
NOTICE
When motors are connected in parallel,
parameter 1-29 Automatic Motor Adaptation (AMA) cannot
be used.
NOTICE
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor protection for the
individual motor in systems with parallel-connected
motors. Provide further motor protection with
thermistors in each motor or individual thermal relays.
Circuit breakers are not suitable as protection.
LC lter
Illustration 4.15 Installations with Cables Connected in a
Common Joint
MG16I302
Operating Instructions
Problems are possible at start and at low RPM values if
motor sizes vary widely. The relatively high ohmic
resistance in the stator of small motors calls for a higher
voltage at start and at low RPM values.
for
M,N

4.9.4 Motor Thermal Protection

The electronic thermal relay in the frequency converter has
received UL-approval for single motor protection, when
parameter 1-90 Motor Thermal Protection is set for [4] ETR
Trip 1 and parameter 1-24 Motor Current is set to the rated
motor current (see motor nameplate).
For the North American market: The ETR functions provide
class 20 motor overload protection in accordance with
NEC.
For motor thermal protection, it is also possible to use the
®
VLT PTC Thermistor Card MCB 112. This card provides
ATEX certification to protect motors in explosion hazardous
areas, Zone 1/21 and Zone 2/22. When
parameter 1-90 Motor Thermal Protection is set to [20] ATEX
ETR and MCB 112 are combined, it is possible to control an
Ex-e motor in explosion hazardous areas. Consult the
Programming Guide for details on how to set up the
frequency converter for safe operation of Ex-e motors.
4.9.5 Voltage/Current Input Selection
(Switches)
The analog mains terminals 53 and 54 allow setting of
input signal to voltage (0–10 V) or current (0/4–20 mA).
See Illustration 4.13 and Illustration 4.14 for the location of
the control terminals within the low harmonic drive.
Default parameter settings:
•
•
NOTICE
REMOVE POWER
Remove power to the low harmonic drive before
changing switch positions.
1.
2.
3.
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Terminal 53: Speed reference signal in open loop
(see parameter 16-61 Terminal 53 Switch Setting).
Terminal 54: Feedback signal in closed loop (see
parameter 16-63 Terminal 54 Switch Setting).
Remove the LCP (see Illustration 4.16).
Remove any optional equipment covering the
switches.
Set switches A53 and A54 to select the signal
type. U selects voltage, I selects current.
4 4
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