Memdos LP diaphragm dosing pumps are fitted with an EC motor. These provide a higher degree of efficiency than a 3-phase asynchronous motor with external frequency converter with a comparable performance.
Available in a number of material designs, with delivery capacities of between 4 - 1,010 l/h at up to 16 bar backpressure, the feed units provide an energy-efficient alternative to the 3-phase motor.
Those involved with the energetic efficiency of electrical motors are inevitably forced to deal with the standard IEC 60034-30. This standard regulates the design of 3-phase cage rotor asynchronous motors. The standard classifies them under the efficiency class (IE1-IE4). This applies to electric motors in the capacity range from 0.75 kW - 375 kW. The majority of classical motor-driven diaphragm dosing pumps with a high delivery capacity of between 4 and 1.010 l/h are usually equipped with a 3-phase asynchronous motor as an electrical drive. Nevertheless, the electrical capacity of the drives is usually located below the minimum performance threshold of 0.75 kW stated in the standard. As a result, it is exempted from its specifications. Equipped with an EC motor, the diaphragm dosing pump Memdos LP from Lutz-Jesco represents an energy-efficient solution.
Advantages of the EC motor
An EC motor (electronically commutated motor) is a brushless DC motor fitted with dedicated power and control electronics. Its commutation, the alternating current feed to the individual stator branches is performed via semi-conductor elements and not as with a standard DC motor mechanically via carbon brushes. This form of "electronic commuting" and the absence of carbon brushes bring a considerable increase in the service life. Apart from the motor bearings, there is little mechanical wear. Moreover, this avoids "brush arcing", which at high speeds, can result in increased brush wear and a reduced service life. "Brush arcing" also produces electromagnetic malfunctions through feedback.
The permanent magnet fitted on the rotor generates less inertia than a standard DC motor, increased dynamism and more compact exterior dimensions. With a sensor for each stator branch, the motor is able to switch the current feed depending on the rotor position. The nature of the current feed in an EC motor allows high torque values at even low speeds. These design features produce an efficiency > 90 %. According to the directive, a 3-phase motor in IE3 design with comparable capacity comes to an efficiency > 82 %. If the drive has an adjustable speed, it is necessary to calculate for a fitting external frequency converter. The design of the EC motor in contrast is inseparably connected with its power electronics into a single unit, even with the measurement of its efficiency.
The perfect combination
Depending on the model, the new Memdos LP is fitted with EC motors with three different capacity stages: 250 W, 550 W or 650 W. Apart from the model with a 650 W motor, the cooling is performed via free convection (i.e. no additional fan), which contributes to the increase in efficiency. Moreover, the pump can be operated permanently at a low delivery capacity without requiring a separate fan. Forming a single unit, the power electronics and motor package are both located in a single housing. In theory, the working torque is available even at the lowest of speeds. The Memdos LP switches into start-stop mode from a lower threshold speed in order to guarantee the filling of the dosing head at all times. This threshold lies underneath that of a motor with an eternal frequency converter, as the torque falls from a threshold of ca. 30% of the max. speed
Continual sensor monitoring of the pump drive makes the diaphragm pump well-suited to highly-precise dosing applications. Fitted with an entirely newly-developed TPU (thermoplastic polyurethane) diaphragm, the HP (High Performance) variations enable an over 30 % increase in the delivery capacity and continual backpressure of up to 16 bar with an identical motor-gear combination.
An intuitive operating concept
On the control side, the Memdos LP is fitted with a letter-quality display and four multi-functional pushbuttons. The menu is clearly structured in a manner similar to a mobile telephone. On the connection side, the feed units are fitted with an analogue input (0/4 - 20 mA), an impulse input, a fault signalling relay, external start-stop button, a stroke feedback output and a 2-stage level input. The Memdos LP is fitted with an analogue output (0/4 - 20 mA) as standard. The time and batch modi can be parameterised on the software. Diaphragm monitoring and a double diaphragm system are optionally available. The fully-integrated process pump can be fitted with an industrial Ethernet interface which communicates via the Modbus TCP protocol.
Economic considerations alone favour the 3-phase asynchronous motor, for situations requiring a pump without an adjustable speeds. The elimination of the control electronics in the form of a converter brings cost advantages. In this application, the Memdos LB convinces with its tried-and-tested motor concept and a manual stroke length adjustment.