IMPORTANT INFORMATION FOR
The 'Easy' Way to specify
Variable Speed Drives for Food
and Beverage Applications
By Kevin Brown, Managing Director Quantum Controls Ltd
Finding the correct VSD or motor
controller can be a fairly daunting task as
there are many variables with each F & B
application and system. However, below
are some helpful tips and suggestions to
help you select the right drive. Hopefully,
the mystery becomes less complex as you
understand what your specific industry
application needs are.
The Application
Before you get too far into the process of
looking at VSDs, it is a good idea to gather
the basic motor and system information
that will help you in selecting the proper
VSD. Most of this information can be
found on your motor nameplate such as:
•
Kilo Watt Power
•
Full Load Amps (FLA)
•
Voltage
•
RPM
•
Service Factor
•
It is also helpful to know if the motor
is inverter duty rated
•
Special Enclosure Needs
Kilo Watt (kW)
Although it is important to size the
VSD with the FLC of the motor(s) being
controlled, knowing the kilowatt of the
load is a great way to search for drives
that may fit your application to be further
narrowed down by other variables.
Full Load Current (FLC)
Using the FLC rather than horsepower
ratings is the proper way to size a VSD.
You will want to compare the motor with
the amp ratings of each VSD you are
considering.
18 FDPP - www.fdpp.co.uk
Voltage
It is crucial to match the voltage of the
VSD and motor to your available voltage
on site. In addition, if continuous operation
is a must, then the following should be
specified:
•
+/- 10% voltage fluctuation
•
+/- 3% frequency variation
Type of Load (Constant Torque or Variable
Torque)
Does your variable frequency drive
application require a variable torque
or constant torque drive? In the Food
and Beverage sector the majority of
applications will be centrifugal pumps and
fans.
Speed Range
Generally speaking, a motor should not be
run at any less than 20% of its specified
maximum speed allowed. If it is run at
a speed less than this without auxiliary
motor cooling, the motor will overheat.
Auxiliary motor cooling should be used
if the motor must be operated at slow
speeds.
Control Method
With 2-wire control, only one switch is
used to run the variable frequency drive.
With 3-wire control, two switches are
used to run the drive. One switch is
needed to stop, and another to start the
variable frequency drive.
Speed Reference Alternatives
•
Speed Potentiometer
•
Digital Programming / Display Unit
•
Analog Signal Follower
•
Selector switch speed selection
•
Serial Communications
Special Enclosure Needs
An important aspect of selecting the right
VSD for your F & B application deals with
the environment surrounding the drive,
with area wash down being common place
special attention should be paid to the IP
Rating of the drive enclosure.
Inverter Duty Rated Motors
Motors all use wire that has been
designed to handle the high voltages that
can occur due to a drive usage. Some
additional recommended features of
inverter rated motors include grounding
rings, isolated bearings and special cooling
features (such as a separate fan to cool
the motor at low speeds, typically on a
constant torque application).
Food and Beverage Custom VSD Builds
At this time you may also consider other
options and VSD accessories such as:
•
Disconnect or Circuit Breaker
•
HOA (Hand/Off/Auto Switch)
•
Pilot Lights
•
Bypass
•
Line Reactor
•
Harmonic Mitigation
•
Door Mounted Interface
•
dv/dt filter
Final Recommendations
This an abbreviated guide for the full
version please visit the resource section
of www.quantum-controls.co.uk to
download for free. If you have any
questions about your application or in
sizing a new VSD call and talk to one of our
application specialists before purchasing
or send your enquiry to
[email protected]
01661 835566