Motor protection isn’t just about specialist protection equipment – modern soft starters perform the job of starting motors more smoothly, and – therefore – reliably into the bargain. In this instance, ABB has expanded its softstarter range with the addition of the PST device:
Suitable for pump, fan, blower, centrifuge, mixer, and conveyor applications, the PST uses closed loop control to closely regulate the starting current to the motor and eliminate current spikes. This minimises the impact of motor starting on the electrical network and also helps to prolong the life of mechanical components such as coupling and belts and gearboxes by preventing unnecessary wear.
As added protection, all PST softstarters also include a soft stop feature. When engaged, the PST soft stop feature results in a slower, gentler stopping of driven loads. This eliminates "hammering" in pumping systems and prolongs the life of gearboxes and drive belts when operating compressors, mixers, and conveyors.
Setting up the PST is made easy by the unit's four-button keypad and LCD display. Using a menu system similar to a mobile telephone, all information is shown in plain text and can be displayed in English, German, Italian, Chinese, Finnish, Swedish, French, Spanish, Dutch, Portuguese and Russian. Operators are also able to set advanced warning parameters, allowing potential problems to be identified before real problems occur. A password protection function is available to prevent unauthorised changes to the programming.
To help reduce set-up time even further, standard settings are available for many common applications such as pump, mixer and crusher drives. The display can also be used to check historical information from the PST's built in event log, which stores data from the last 20 events together with dates and times.
Advanced motor protection is provided by four different overload trip classes, allowing the motor to be fully utilised without nuisance tripping or fear of motor burn-out. The inclusion of multiple trip classes enables one class to be set for the start-up and another one for continuous running, giving dual overload protection. Protection is also provided against locked rotor, phase imbalance, phase reversal and high current. In addition, all devices within the PST Softstarter range can handle continuous over currents of up to 15%.
All PST units have three programmable signal relays where each relay can signal Run, Top of Ramp or Event. The Event setting can be used to signal protections, faults and warnings. The supervisory functions monitor not only software and critical softstarter functionality but also phase loss and out of frequency range.
As well as local operation via the keypad, all PST softstarters can be hard-wired into a centralised control system. They can also be connected to a fieldbus system using ABB's new FieldBusPlug bus connector, which uses a 'neutral' fieldbus-independent interface to enable simple and fast communication with any major fieldbus protocol.
All PST softstarters are ABB IndustrialIT enabled, with all the information required for integration into larger systems already built into the device. It also incorporates functions that permit seamless integration into real-time automation systems.
The picture shows the new softstarter range from ABB.