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VLT
®
6000 HVAC
MG.60.B1.02 - VLT is a registered Danfoss trademark
26
2.05
Protective Features
A. Class 20 I
2
t electronic motor overload protection
for single motor applications and thermal-
mechanical overloads for multiple motor
applications.
B. Protection against input transients, loss of AC line
phase, short circuit, ground fault, overvoltage,
undervoltage, frequency converter
overtemperature and motor overtemperature. The
frequency converter shall display all faults in plain
text. Codes are not acceptable.
C. Protection of frequency converter from sustained
power or phase loss. The frequency converter
shall incorporate a 300 msec control power loss
ride through to eliminate nuisance tripping.
D. The frequency converter shall incorporate a motor
preheat circuit to keep the motor warm and
prevent condensation build up in the stator.
E. The frequency converter shall incorporate a run
permissive function, which will exports a "run
permissive standby" signal to a digital output,
when a start signal is applied to the frequency
converter. The frequency converter must not start
until it receives a "ready" signal from an external
contact.
F. The frequency converter shall incorporate 4 skip
frequencies with adjustable bandwidth, to prevent
mechanical resonances from destroying the
equipment.
G. To prevent breakdown of the motor winding
insulation, the U
PEAK
must be below 1000 V. The
supplier shall include with the quotation the U
PEAK
values of the frequency converter.
H. The frequency converter shall catch a rotating
motor operating forward or reverse up to full
speed to prevent nuisance tripping.
I.
A thermistor input must be available in the
frequency converter.
J. The frequency converter shall incorporate
constant torque start to prevent nuisance tripping.
K. Automatic adjustment of the ramp time, to prevent
tripping, must be incorporated in the frequency
converter.
C. The frequency converter shall include Automatic
Motor Adaptation (AMA), to optimize motor
performance, improve start capabilities and
compensate for motor cable variances. AMA shall
be carried out at motor standstill with no need for
detaching the load from the motor.
D. The frequency converter and options shall be
tested to ANSI/UL Standard 508. The complete
frequency converter, including all specified
options, shall be listed by a nationally recognized
testing agency such as UL, C-UL, ETL or CSA.
E. The frequency converter shall have a DC link
reactor integrated to minimize power line
harmonics. There shall be reactors in both the
positive and negative rails. Frequency converters
without a DC link reactor shall provide 3%
impedance AC line reactors.
F. The frequency converter's full load amp rating
shall meet or exceed NEC Table 430-150.
G. The frequency converter shall be able to provide
full rated output current continuously, 110% of
rated current for 60 seconds and 160% torque for
up to 5 seconds for high inertia and high friction
loads.
H. An automatic energy optimization feature shall be
provided as standard in the frequency converter.
This feature shall reduce voltages when the motor
is lightly loaded and minimise the motor losses.
I.
For additional energy savings the frequency
converter must be able to turn itself off, when
operation does not serve a purpose as determined
by the control signal. To prevent the frequency
converter from turning on and off all the time, a
Boost setpoint must be selectable.
J. The frequency converter fan must automatically
turn off at low temperatures.
K. Unlimited output power circuit switching must be
possible without the need for control circuit
interlocking and without causing damage to the
frequency converter.