As technology progresses, soft starters are becoming more sophisticated, providing more protection and more detailed feedback.
During motor starts and stops AuCom's EMX3 starter with its built-in adaptive acceleration control algorithm learns the attached motor's dynamic performance and then adjusts control to optimise performance. The starter offers a high degree of application customisation and the dynamic learning speeds set-up. The compact size and design enable multiple units to be mounted side by side, or in starter banks.
Adaptive acceleration control
Traditionally soft starters have used techniques such as timed voltage ramp, constant current and torque control to soft start and stop motors, but none directly controlled acceleration. XLR-8 adaptive acceleration control influences starting current and torque to achieve this.
The controller measures the motor's operating characteristics during each start to create two reference points: motor characteristics at zero speed and motor characteristics at maximum efficiency. During each subsequent start and stop the starter compares the motor's performance characteristics with these reference points to estimate the motor's speed as a series of values between zero and 100%. All the user needs to do is select the profile that best matches the load type and the soft starter automatically ensures the smoothest possible acceleration for the load.
Start and stop profiles
The XLR-8 algorithm offers three starting and stopping profiles, which relate motor speed to elapsed time. Depending on application requirements users can select early, constant or late acceleration/deceleration. During a start or stop, the starter compares the estimated motor speed with the selected profile and adjusts its behaviour accordingly. If the estimated speed is lower than the profile suggests, more power is applied to the motor. Conversely if the estimated speed is higher than the profile, less power is applied.
Braking
For high inertia loads, the braking algorithm provides precise control over the motor's stopping time. Shorter stopping times help improve production efficiency by reducing downtime between operating cycles.
Pumping applications
Gradual and shock free acceleration can benefit all motor applications, but many situations benefit from more precise control of acceleration and/or deceleration.
Pumping applications may require special attention to reduce transients and associated water hammer, which can benefit from the application of acceleration control.
In situations with high back pressure a late deceleration stop will result in a gentle flow/no flow transition eliminating pump turbining and the rapid closure of the non-return valve.
When stopping a pump operating in a system with low head and high flow rate a long uniform deceleration prevents a sudden low pressure state behind the pump which would cause the non-return valve to slam shut and send shock waves through the system.
Problems can be experienced with pumps losing prime in open systems such as when pumping water from a lake to a higher channel. When the pump stops, water rapidly drains back through the pump causing it to turbine and leaving the chamber unprimed if there is no non-return valve. A quick, then slow deceleration stops water being pumped but still keeps the pump rotating in a forward direction while water remaining in the pipe work drains slowly back through leaving the pump primed for the next start.
Other applications
To meet the requirements of other applications, the EMX3 includes a range of advanced features aimed squarely at solving issues in specific applications. Acceleration control can be applied to pre-tension conveyor belts, helping to reduce wear and to provide constant acceleration on people movers, for safety and comfort. The built-in timers can benefit irrigation applications. The auto-reset function can be used for flood pumps.
Configuration
The large screen of the removable configuration interface gives real-language feedback messages, removing the need to look up codes to understand motor status. Realtime metering displays and time-stamped event logging provide user insight into motor behaviour.
A remote mounting kit can be used to fit the keypad and display on the enclosure exterior. Remote mounting eliminates the need for separately wired accessories since it replaces an amp meter, volt meter or power meter, displays hours run and provides a current graph.
The removable keypad can also be used to transfer EMX3 configurations between controllers.
An alternative approach is to use AuCom's WinMaster software to control, monitor and program the starters from any desktop computer.
Simulation
To assist in commissioning AuCom have built in simulation features that can test the installation prior to connecting the motor. The simulation functions test the soft starter's operation, external control circuits and associated equipment without connecting to line voltage or motor. There are three simulation modes:
* Run simulation: simulates a motor starting, running and stopping to ensure correct installation.
* Protection simulation: simulates activation of each protection mechanism to confirm correct protection response.
* Output signalling simulation: simulates output signalling.
Emergencies
In the event of an SCR failure the EMX3 has a 'power through' mode which allows users to select continuous operation despite a power assembly failure. This allows production to continue while remedial action is taken. For more extreme circumstances like a fire, 'emergency run' mode can be activated. This will initiate a start and deactivates all protection systems enabling the motor to run as long as possible despite the deteriorating environment.
Options
The EMX3 has a range of optional accessories for more specific functionality including network communication using Profibus, DeviceNet or Modbus RTU modules; hardware expansion cards that add inputs and outputs; and an RTD and ground fault protection card that adds six PT100 RTD inputs and one ground input.
Bus bars on the larger models can be adjusted for top or bottom input and output as required.
For more information contact Rob Hare, CHI Control Components, +27 (0)11 824 7400, [email protected], www.chi.co.za
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