VLT
®
6000 HVAC
MG.60.B1.02 - VLT is a registered Danfoss trademark
28
V. The frequency converter will sense the loss of load
and signal a no load/broken belt warning or fault.
W. The frequency converter shall store in memory the
last 10 faults and record all operational data.
X. Eight programmable digital inputs shall be
provided for interfacing with the system‘s control
and safety interlock circuitry.
Y. Two programmable relay outputs shall be provided
for remote indication of frequency converter
status.
Z. Three programmable analog inputs shall be
provided and shall accept a direct-or-reverse
acting signal. Analog reference inputs accepted
shall include 0-10 V DC, 0-20 mA and 4-20 mA.
AA.Two programmable analog outputs shall be
provided for indication of frequency converter
status. These outputs shall be programmable for
output speed, voltage, frequency, amps and kW.
BB.Under fire mode conditions the frequency
converter shall automatically default to a preset
speed via a normally open (NO) contact.
2.07
ADJUSTMENTS
A. The frequency converter shall have an adjustable
switching frequency of 2 to 10 kHz.
B. It must be possible for the frequency converter to
automatically adjust the switching frequency as
high as possible, without derating, to reduce
acoustic noise in the motor.
C. The voltage/frequency ratio shall automatically be
adjusted to minimize motor losses.
D. A variable torque curve for parallel motors shall be
available. The start voltage must be adjustable.
E. It must be possible to obtain 160% break away
torque for at least 0.5 sec.
2.08
BYPASS
A. Where indicated on the drawings, the frequency
converter is to be provided with a manual bypass
consisting of a door interlocked main fused
disconnect pad lockable in the off position, a
built-in motor starter and a four position DRIVE/
OFF/LINE/TEST switch controlling three
contactors. In the DRIVE position, the motor is
operated at an adjustable speed from the
frequency converter. In the OFF position, the
motor and frequency converter are disconnected.
In the LINE position, the motor is operated at full
speed from the AC power line and power is
disconnected from the frequency converter, so
that service can be performed. In the TEST
position, the motor is operated at full speed from
the AC line power. This allows the frequency
converter to be given an operational test while
continuing to run the motor at full speed in
bypass. Customer supplied normally closed dry
contact shall be interlocked with the frequency
converters safety trip circuitry to stop the motor
whether in DRIVE or BYPASS mode in case of an
external safety fault.
B. The bypass shall be made such that the Run
Enable Function will operate in bypass mode.
F. 4 Setups must be provided to allow changing
between different operating modes, such as from
normal operation to fire mode.
G. Eight acceleration and eight deceleration ramps
shall be provided. The shape of these curves shall
be adjustable.
H. Four current limit settings shall be provided.
I.
If the frequency converter trips on one of the
following conditions, the frequency converter shall
be programmable for automatic or manual reset:
undervoltage, overvoltage, current limit, inverter
overload and motor overload.
J. The number of restart attempts shall be selectable
from 0 through 20 and the time between attempts
shall be adjustable from 0 through 600 seconds.
