Posts Tagged jet pumps

Existing methods of reducing the starting currents of jet pumps.

Apr 23

Posted by Edmundo Plumber in Grundfos pumps, Plumbing supplies, Water pumps | Comments off

Their implementation in the case of convertiblejet pumps Grundfos

As a rule, well pumps, the following ways to reduce the starting currents of pumps: direct integration; inclusion of the method of “star-triangle”, the method including the electric pump through a start-up transformer; smooth start and frequency converter When choosing a method of reducing the starting current should be considered part of the pumping equipment, technical requirements, as well as the rules and regulations of electric service.

The direct inclusion

When actuated, contactor or similar device connected to the network directly. All other things being constant parameters DÖL is the way to start, which occurs in the pump minimum amount of heat and thus have jet pumps up to 45 kW provides maximum durability. However, the electric power greater mechanical load is so high that it is recommended to lower currents.

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Method of setting the starting jet pump through a transformer

Apr 23

Posted by Edmundo Plumber in Plumbing supplies, Water pumps | Comments off

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.

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The negative factors arising from the use of electric convertible jet pumps

Apr 23

Posted by Edmundo Plumber in Plumbing supplies, Water pumps | Comments off

At the organization of water supply based on groundwater use technological modes of operation of water wells include convertible jet pumps starting modes, whose number can reach 30 puskovostanovok per hour (see Table. 1). Start convertible well jet pump is one of the worst regimes for their pumps, pipes and water-lifting of the well. Electric convertible jet pump at this time for a short time exposed to the peak load, as its start-up current, again, 4 – 7 times higher than the nominal value at a relatively low starting torque.

In addition, the jump start current creates a shock electromagnetic torque that is transmitted through the shaft of the engine to the pump impeller. Under such conditions, water-lifting the pipe string may be the maximum pressure fluctuation in the hydraulic shock, and in part – high values ​​of the flow of water into the well from the aquifer.

At the same time to start mode is characterized by two periods:

❏ first (t1 = 0,9-0,5 s), within which there are high velocities of water influx into the well from the aquifer at the top of the filter. Also, there is a sharp change in pressure, which violates the stability zone (there is sand);
❏ second (t2 = 1-5 s) under certain conditions, accompanied by a water hammer in the pressure pipe.

To eliminate the negative effects of transients that occur at the start of convertible jet pumps, technological schemes of equipment wells. They are based on the electric (using devices that change the number of revolutions of the pump), the regulation of water supply and hydraulic convertible jet pumps (with shut-off and control valves) principles. This article focuses on the electrical component of the solution to the problem and its impact on energy use of pumping equipment.

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