ECO REFERENCE MANUAL
16-3
1.
General
•
The VSD shall be purposely designed and
manufactured for HVAC (Heating Ventilation
and Air Conditioning) applications. The VSD
shall be suitable for all loads with variable
torque characteristics, such as fans and
pumps.
•
The VSD shall be capable of starting and
running high inertia loads such as centrifugal
fan equipment.
•
The VSD supplier shall carry a comprehensive
range of spares which shall continue to be
available for at least 5 years after the
production of the particular VSD model has
been discontinued.
•
The VSD and motor shall preferably be
manufactured by the same firm in order to
ensure VSD and motor performance matching
as well as optimum total system efficiency.
•
The VSD shall also be compatible for use with
the various asynchronous squirrel cage
induction motors typically used by
manufacturers of HVAC equipment.
•
The VSD shall be of sufficient capacity and
shall produce a quality low distortion output
waveform so as to achieve full rated
nameplate shaft power output of the motor.
The VSD shall be capable of operating any
standard squirrel cage induction motor of the
specified VSD power rating without any
modifications to the motor or the VSD.
2.
Design
•
The VSD shall be fully digitally controlled
utilising PCB surface mounting technology and
VLSI.
•
The VSD shall consist of the following
major components:
1. Full-wave bridge 6 pulse Rectifier.
2. DC link capacitors.
3. Inverter stage with Insulated Gate Bipolar
Transistor (IGBT) power modules across
the entire range (GTO or BJT devices shall
not be acceptable).
4. Control and display panel.
•
The VSD shall have high efficiency and have
low maintenance requirements. The VSD
shall provide an adjustable output frequency
and voltage utilising the principles of Pulse
Width Modulation (PWM) design. This
technique shall provide full nameplate motor
voltage as well as distortion free sinusoidal
currents at the terminals of the motor in order
to obtain full motor rated torque at rated
frequency. The PWM strategy shall be of the
Space Vector Modulation type implemented
through a microprocessor and ASIC in order
to operate with optimum power and efficiency,
minimise acoustic noise produced by the
motor and reduce motor heating created by
output harmonics.
The operating characteristics shall not exceed
those which are recommended by the motor
manufacturer.
•
The mechanical design of VSD shall adhere to
the following guidelines;
1. The internal layout of the VSD shall
maintain separation between the control
signals and the power conductors in order
to minimise EMC noise related problems
2. The VSD shall be assembled in such a way
as to facilitate easy maintenance
3. Control signal wiring installation shall be
simplified through the use of screwless
terminal design.
4. The location of the nameplate or label of
the VSD shall be easily accessible and
contain all the necessary information in
order to determine the VSD rating and to
also assist with identification