Food & Drink Process & Packaging Issue 10 2016 - Page 18

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 sales@quantum-controls.co.uk 01661 835566