With this method, start-up the voltage is reduced by transformers (usually two), one for each phase. Transformers often have two network output: one for the other 75% and 60%. If you use 60% of output is reduced starting current, similar to the method of launching “a star-delta.”
When starting the jet pumps gets the first low voltage, and then complete. When switching the transformer connected to a choke coil. This means that the pump always remains connected to the network and its rotation rate is not reduced. Power consumption at start-up is shown in the diagram. Start-up transformers are relatively expensive, but very reliable. Naturally, the inrush current is determined by the characteristics of the pump and pump, and depending on their sizes can vary considerably.
Soft start pump (SS)
A device for pump starter is an electronic device that reduces the voltage and inrush current, respectively, by phase control. The electronic device comprises adjusting unit, configured with a variety of operational and safety parameters and the power unit with a symmetric Triac. Inrush current is limited, as a rule, the value in two to three times the rated current. When you save the other options off the pump by this method also provides a reduction in the initial starting point. The presence of inertia in the process of start-up can lead to significant heat buildup in the pump and thereby reduce its service life. However, this problem with a short acceleration / deceleration time, for example, for 3 s, has no practical value. This statement also applies to pump launch on the methods of SD (the inclusion of a “star-triangle”) and AF (through the inclusion of start-up transformer). Thus, the operation of downhole pumps, Grundfos are advised to observe for the starter shown in the graph (Fig. 4), the acceleration / deceleration.
In that case, if you want a particularly high starting torque, starting voltage can be increased by 55%. However, under normal operating conditions is required.
For a smooth start-up switch allows the pump to supply non-sinusoidal current form and to some extent, creates higher harmonics. Due to the very short acceleration / deceleration from a practical point of view (and in the rules relating to the higher harmonics), it does not find much use.
In general, the starter switch is recommended to install a roundabout at the contractor to the pump during operation operated in DÖL. This ensures minimal wear and loss of power in the device to the starter. In that case, if the soft-start pump is made through a bypass contractor, they can work with the thermal protection system (Temrson).
Start by a frequency converter
Start the Floforce jet pump by the inverter is ideal from the standpoint of reducing the starting current, and pulse pressure. Diagram of the start-up.
The advantage of this method is that the inrush current at all times hold at the level of the nominal current. This means that the number of required hours for on and off can be set to any. In some models, such as SQ and SQE pumps feature soft start and stop due to the frequency converter is built for easy installation and operation.