Industrial centrifugal pumps are now almost exclusively controlled by frequency converters in the plant's control system. In this article, Daniel Gontermann and Alexander Wurzbacher, two engineers at KSB Pump Company, discuss a solution for installing a frequency converter on a motor to control the speed of a centrifugal pump with power up to 45 kW so that all The factory engineering standard motor is integrated. The plant owner usually views the variable frequency pump system as three separate sections during the planning or refurbishment of the pumping unit. One of the reasons for this is to foresee the technical complexity; in addition to the nominal flow and discharge head, the plant owner must consider many other important factors. These factors include: the characteristics of the product being processed, the temperature range of the product and various design and construction specifications. When selecting a motor, it is usually the reference to the relevant engineering standards and to the specific motor specification and manufacturer. Finally, the drive specialist selects the appropriate drive based on the current value of the specified motor. Such a variety of technical requirements require a variety of independent pumping solutions. However, for any pump manufacturer, such a complete, ready-to-buy pump set does not economically meet a wide range of application needs. To benefit from a similar overall design solution, KSB Aktiengesellschaft in Frankenthal, Germany, has developed a motor mounting solution to control the rotational speed of a 45 kW centrifugal pump. Unlike off-the-shelf integrated motors, this newly developed driver is suitable for all brands of motors that meet factory engineering standards. The Perfect Match The factory owner will also get a complete set of off-the-shelf pumping equipment, and they have many advantages over those who currently use box drives. Now, the factory owner will get the perfect match for the pump assembly from the pump manufacturer, including pumps, motors and frequency converters. Once the power is turned on, all parameters required for commissioning are set in the factory. Proportional Integral (PI) controllers are used to ensure differential pressure and control outlet pressure and temperature without additional equipment. Some of the related instrumentation is installed in the pump housing, and due to the intelligent operating point adjustment technology, some components can be reduced. The same process is used to install the pump to the pipe system, regardless of whether variable frequency control is used or not, and no additional cost or time is required to commission the variable speed pump. Compared with the box-type inverter widely used at present, the mode of installing the inverter on the motor has many advantages. It is up to the manufacturer of the pump to be responsible for the good work of all the components, not the designer of the equipment; there is no need to check the interface of the components before and during assembly; the purchaser only has to track one delivery time without having to negotiate with a different supplier Buy pumps, motors, frequency converters, motor cables, signal cables and other auxiliary materials. System debugging has also been a considerable simplification. In the days when many factory owners also adopted standard frequency converters, it was often necessary to involve professionals in hydraulics and electronics engineering to achieve such good levels of system performance among each other. Energy Savings Reducing Energy Savings Rely on the ability to set the drive's V / f (voltage / frequency) performance curve as a quadratic law load. After all, running a centrifugal pump requires very little torque, and when a gravel conveyor system is started, the torque required is much higher. The number of cables required for box-mounted inverter can not be ignored. Depending on the distance between the motor and the frequency converter it is important to decide whether a shielded or unshielded cable or sine filter is required. In addition, not every drive can handle thermistor signals mounted on the motor. In order to obtain information on the hydraulic operating conditions of the system, it is up to the specialist to use and analyze the current, frequency and power input data provided by standard frequency converters. This requires a considerable amount of experience and is beyond the reach of those who have only been trained in basic electrical technologies. Since the data generated by the standard drive is not pre-configured for hydraulic applications, even those with relevant knowledge may have incorrect results. The use of frequency control pumping system will significantly reduce the investment in industrial applications and operating costs. The system selection process becomes simple and there is generally no need for shielded cable connections between the motor and the drive, which is far superior to the costly procurement of drive equipment. Other hydraulic functions such as Dynamic Pipeline Friction Compensation or Sensorless Runaway Protection and alarm alerts when the pump is running in low flow conditions help to prevent damage to the pump and system and to reduce its operational life Long, while life cycle costs are reduced. If the system is equipped with a pressure sensor, it automatically recognizes and ensures that the drive is set in controlled operation. Running six pumps in parallel with PumpDrive can run in parallel without additional equipment. The communication between the pumps is done by the bus. The main pump transfers the work points needed to reach the common set-point to other pumps and minimizes the overall system's energy consumption as much as possible. Plain text data on the main pump user interface provides information on operating status, flow rate, outlet head pressure, and total pump displacement. In the eyes of the factory designer, the variable speed pump is an interface of the entire system is simple and clear automatic function unit. The manufacturer will be responsible for the entire pumping system and its energy-saving operation, even under fluctuating load conditions. Plant engineers benefit from reduced installation and commissioning costs, even when retrofitting existing constant-speed pump systems. Cost savings are mainly achieved through streamlined project planning, streamlined procurement processes, reduced installation space, lower cable expenses, simplified commissioning and low failure rates resulting from low-flow operation avoidance. "Motor-mounted" variable-speed drives show advantages and flexible system design possibilities that will ensure that this solution will be used in the industrial sector in the future, just as today's variable-speed pumps are widely used in buildings. Contact KSB Aktiengesellschaft Johann-Klein-Strasse 9 D-67225 Frankenthal Germany Phone: +49 6233 860 Fax: +49 6233 863401 E-mai: www.ksb.com
