Do-it-yourself smooth start-up of a borehole pump. Analysis of technical solutions: soft starters, variable frequency drive or parallel control circuit for centrifugal pumps. Two-phase starting circuit
Who wants to strain, spend their money and time on the re-equipment of devices and mechanisms that already work perfectly? As practice shows - many. Although not everyone in life is faced with industrial equipment equipped with powerful electric motors, they constantly meet, albeit not so voracious and powerful, electric motors in everyday life. Well, everyone used the elevator, for sure.
Are motors and loads a problem?
Probably, the most significant load that falls on the engine at the time of start-up is a multiple, albeit short-term, excess of the rated operating current of the unit. After a few seconds of operation, when the electric motor reaches its nominal speed, the current consumed by it will also return to normal levels. To ensure the necessary power supply have to increase the capacity of electrical equipment and conductive lines which drives up their prices.
At startup powerful electric motor, due to its high consumption, there is a “drawdown” of the supply voltage, which can lead to failures or failure of equipment powered with it from the same line. In addition, the service life of power supply equipment is reduced.
In the event of emergency situations that caused the engine to burn out or its severe overheating, properties of transformer steel may change so much so that after repair the engine will lose up to thirty percent of power. Under such circumstances, it is no longer suitable for further operation and requires replacement, which is also not cheap.
What is a soft start for?
It would seem that everything is correct, and the equipment is designed for this. But there is always a "but". In our case, there are several:
- at the moment of starting the electric motor, the supply current can exceed the rated one by four and a half to five times, which leads to significant heating of the windings, and this is not very good;
- starting the engine by direct connection leads to jerks, which primarily affect the density of the same windings, increasing the friction of the conductors during operation, accelerates the destruction of their insulation and, over time, can lead to an interturn short circuit;
- the aforementioned jerks and vibrations are transmitted to the entire driven unit. It's really unhealthy because may cause damage to its moving parts: gear systems, drive belts, conveyor belts, or just imagine yourself riding in a twitching elevator. In the case of pumps and fans, this is the risk of deformation and destruction of turbines and blades;
- do not forget about products that may be on the production line. They may fall, crumble or break due to such a jerk;
- Well, and probably the last of the points that deserve attention is the cost of operating such equipment. We are talking not only about expensive repairs associated with frequent critical loads, but also about a tangible amount of inefficiently spent electricity.
It would seem that all of the above operating difficulties are inherent only in powerful and bulky industrial equipment, however, this is not so. All this can become a headache for any average layman. First of all, this applies to power tools.
The specifics of the use of such units as electric jigsaws, drills, grinders and the like involve multiple start and stop cycles within a relatively short period of time. This mode of operation, to the same extent, affects their durability and energy consumption, as well as their industrial counterparts. With all this, one should not forget that soft start systems unable to control engine speed or reverse their direction. It is also impossible to increase the starting torque or reduce the current below what is required to start the rotation of the motor rotor.
Video: Soft start, adjustment and protection of the collector. engine
Options for soft start systems for electric motors
Star-delta system
One of the most widely used starting systems for industrial asynchronous motors. Its main advantage is simplicity. The engine starts when the windings of the star system are switched, after which, when the nominal speed is set, it automatically switches to delta switching. This kind of start allows you to achieve a current almost a third lower than with direct start of the electric motor.
However, this method is not suitable for mechanisms with small rotational inertia. These include, for example, fans and small pumps due to the small size and weight of their turbines. At the time of the transition from the "star" to the "delta" configuration, they will sharply reduce speed or stop altogether. As a result, after switching, the electric motor essentially restarts. That is, in the end, you will not only achieve savings on the engine resource, but, most likely, you will get an overrun of electricity.
Video: Connecting a three-phase asynchronous motor with a star or delta
Electronic motor soft starter
Smooth start motor can be produced using triacs included in the control circuit. There are three schemes for such inclusion: single-phase, two-phase and three-phase. Each of them differs in its functionality and final cost, respectively.
These schemes usually it is possible to reduce the starting current up to two or three nominal. In addition, it is possible to reduce the significant heating inherent in the aforementioned star-delta system, which contributes to an increase in the service life of electric motors. Due to the fact that the engine start is controlled by reducing the voltage, the acceleration of the rotor is carried out smoothly, and not abruptly, like in other schemes.
In general, several key tasks are assigned to engine soft start systems:
- the main one - lowering the starting current to three or four nominal;
- reduction of the motor supply voltage, in the presence of appropriate capacities and wiring;
- improvement of starting and braking parameters;
- emergency protection of the network against current overloads.
Single-phase starting circuit
This scheme is designed to start electric motors with a power of not more than eleven kilowatts. This option is used if it is necessary to soften the impact at start-up, and braking, soft start and lowering the starting current do not matter. First of all, because of the impossibility of organizing the latter in such a scheme. But due to the cheaper production of semiconductors, including triacs, they are discontinued and rarely found;
Two-phase starting circuit
Such a scheme is designed to regulate and start engines with a power of up to two hundred and fifty watts. Such soft start systems sometimes equipped with a bypass contactor to reduce the cost of the device, however, this does not solve the problem of asymmetric power supply of the phases, which can lead to overheating;
Three-phase starting circuit
This circuit is the most reliable and versatile soft start system for electric motors. The maximum power of the motors controlled by such a device is limited exclusively by the maximum thermal and electrical endurance of the triacs used. His versatility allows you to implement a lot of functions such as: dynamic brake, flyback or magnetic field and current limiting balancing.
An important element of the last of the mentioned circuits is the bypass contactor, which was mentioned earlier. He allows to ensure the correct thermal regime of the soft start system of the electric motor, after the engine has reached its normal operating speed, preventing it from overheating.
The soft starters of electric motors that exist today, in addition to the above properties, are designed for their joint operation with various controllers and automation systems. They have the ability to turn on at the command of the operator or the global control system. Under such circumstances, at the time of switching on the loads, interference may occur that can lead to malfunctions in the automation, and therefore, it is worth taking care of protection systems. The use of soft start circuits can significantly reduce their impact.
DIY soft start
Most of the systems listed above are actually inapplicable in domestic conditions. First of all, for the reason that at home we rarely use three-phase asynchronous motors. But collector single-phase motors - more than enough.
There are many schemes for the smooth start of engines. The choice of a specific one depends solely on you, but in principle, having certain knowledge of radio engineering, skillful hands and desire, it is quite you can assemble a decent homemade starter which will prolong the life of your power tool and household appliances for many years.
There are many reasons to turn on domestic pumps through a soft starter.
Usually, a submersible or surface pump is connected through an electromechanical or electronic relay, an automation unit or a magnetic starter. In all these cases, mains voltage is supplied to the pump by closing the contacts, that is, through a direct connection. This means that we apply full mains voltage to the stator windings of the electric motor, and the rotor does not yet rotate at this time. This leads to the appearance of an instant powerful torque on the rotor of the pump motor.
This connection scheme is characterized by the following phenomena when starting the pump:
Current surges through the stator (respectively, through the supply wires), since the rotor is short-circuited.
In a simplified sense, we have a short circuit on the secondary winding of the transformer. According to our experience, depending on the pump, the manufacturer and the load on the shaft, the pulsed starting current can exceed the operating current from 4 to 8, and in some instances up to 12 times.
The sudden appearance of torque on the shaft.
This has a negative effect on the starting and working stator windings, bearings, ceramic and rubber seals, significantly increasing their wear and reducing their service life.
The appearance of a sharp torque on the shaft leads to a sharp turn of the borehole pump housing relative to the pipeline system.
We have repeatedly witnessed how, because of this, the well pump was disconnected from the pipelines and fell into the well. When pumping station on the basis of a surface pump installed on the accumulator platform, this leads to loosening of the fixing nuts and destruction of the weld points and seams of the accumulator. Also, when the pump is turned on directly, the service life of plumbing and shut-off valves is reduced, especially at their junctions.
It is generally accepted that the accumulator removes water hammer in the water supply system.
This is true, but water hammers disappear in pipelines only starting from the place where the accumulator is connected. In the gap between the pump and the accumulator, when the pump is connected directly, the water hammer remains. As a result, in the interval from the pump to the accumulator, we have all the consequences of a water hammer on all parts of the pump and on the pipeline system.
In water filtration systems, water hammer, which occurs when the pump is directly connected, significantly reduces the life of the filter elements.
If the local power grid weak, then your neighbors will also know about the start of a pump with a power of more than 1 kW with a direct connection by a sharp drop in the voltage in the network at the moment the pump is turned on.
If the local network EXTREMELY WEAK, and your neighbor also enjoys life by connecting all available electrical appliances to the network, then a well pump submerged to a great depth may not start. Such a power surge can damage electronic devices connected to the network. There are cases when, when starting the pump, an expensive refrigerator stuffed with electronics failed.
The more often the pump is turned on, the less its service life.
Frequent starts through a direct connection lead to failure of the plastic couplings of borehole pumps connecting the electric motor to the pump part.
You and I went through the problems that arise when starting the pump without soft starters (UPP) .
It should be noted that even when the pump is turned off without SCP with a direct connection scheme, there are negative points:
When the pump is turned off, a water hammer also occurs in the system, but now for the reason sharp decline torque on the pump shaft, which is equivalent to creating an instantaneous vacuum.
A sharp decrease in the torque on the pump shaft also leads to the rotation of the pump housing, but in the opposite direction.
Think about the pipelines and threaded connections of the pump.
In conventional household pumps, electric motors are asynchronous and have a pronounced inductive character.
If we abruptly interrupt the supply of current through an inductive load, then there is a sharp voltage jump on this load due to the continuity of the current. Yes, we open the contact, and all the high voltage should remain on the pump side. But with any mechanical opening of the contact, the so-called "contact bounce" is present, and the impulses high voltage get into the network, and therefore get into the devices connected at that time to the network.
Thus, when the pump is connected directly, increased wear of the mechanical and electrical parts pump (both at start-up and at shutdown). Devices connected to the same network also suffer, and the service life of filtration systems and plumbing fittings is reduced.
Usage soft starters ("Aquacontrol UPP-2.2S") allows you to smooth out most of the shortcomings described above. In device UPP-2,2S a specially calculated voltage rise curve on the pump is implemented, which allows, on the one hand, to start the pump in the most unfavorable operating conditions, and on the other hand, to smoothly increase the shaft speed. Also, protection against low and high voltage of the mains is built into this device to protect the pump from extreme operating modes and switching on.
IN UPP-2,2S phase triac control is used. At the moment of start-up, a part of the mains voltage is supplied to the pump, which creates a torque sufficient to guarantee the start of the pump. As the rotor spins up, the voltage on the pump gradually increases until the voltage is fully applied. After that, the relay turns on and the triac turns off. As a result, when using UPP-2,2S the pump is connected to the network through the relay contacts, that is, in the same way as with a direct connection. But for 3.2 seconds (this is the soft start time), the pump is energized through the triac, which provides a “soft start”, without sparks on the relay contacts.
With such a start, the maximum starting current exceeds the operating current by no more than 2.0-2.5 times instead of 5-8 times. Using UPP-2,2S, we reduce the starting loads on the pump by 2.5-3 times and prolong the life of the pump by the same amount, provide more comfortable operation of devices connected to the electrical network. UPP-2,2S can be called a device with resource-saving technology.
Soft starter- an electrical device used in asynchronous electric motors, which allows during start-up to keep the motor parameters (current, voltage, etc.) within safe limits. Its use reduces starting currents, reduces the likelihood of motor overheating, eliminates jerks in mechanical drives, which ultimately increases the life of the electric motor.
Purpose
Controlling the process of starting, running and stopping electric motors. The main problems of asynchronous electric motors are:
- the impossibility of matching the engine torque with the load torque,
- high starting current.
During start-up, the torque often reaches 150-200% in a fraction of a second, which can lead to failure of the drive kinematic chain. In this case, the starting current can be 6-8 times higher than the rated current, causing problems with power stability. A soft starter avoids these problems by making the acceleration and deceleration of the motor slower. This allows to reduce starting currents and avoid jerks in the mechanical part of the drive or hydraulic shocks in pipes and valves at the time of starting and stopping the engines.
The principle of operation of the soft starter
The main problem with induction motors is that the moment of force developed by the motor is proportional to the square of the voltage applied to it, which creates sharp jerks of the rotor when starting and stopping the motor, which, in turn, cause a large induction current.
Softstarters can be either mechanical or electric, or a combination of both.
Mechanical devices directly counteract the sudden increase in engine speed by limiting the torque. They can be brake pads, fluid couplings, magnetic interlocks, counterweights with shot, and so on.
Data electrical devices allow you to gradually increase the current or voltage from the initial low level (reference voltage) to the maximum in order to smoothly start and accelerate the motor to its rated speed. Such soft starters usually use amplitude control methods and therefore cope with starting equipment in idle or lightly loaded mode. A more modern generation of soft starters (for example, Energy Saver devices) use phase control methods and therefore are able to start electric drives that are characterized by heavy starting conditions "nominal to nominal". These soft starters allow for more frequent starts and have built-in power saving and power factor correction modes.
Soft starter selection
When an asynchronous motor is turned on, a short-circuit current appears in its rotor for a short time, the strength of which, after a set of revolutions, decreases to a nominal value corresponding to the power consumed by the electric machine. This phenomenon is exacerbated by the fact that at the moment of acceleration, the torque on the shaft also increases abruptly. As a result, the protective circuit breakers may trip, and if they are not installed, then the failure of other electrical devices connected to the same line. And in any case, even if the accident did not occur, when starting the electric motors, there is an increased consumption of electricity. To compensate or completely eliminate this phenomenon, soft starters (SCDs) are used.
How soft start is implemented
To smoothly start the electric motor and prevent inrush current, two methods are used:
- Limit the current in the rotor winding. To do this, it is made consisting of three coils connected according to the "star" scheme. Their free ends lead to slip rings (collectors) attached to the shaft shank. A rheostat is connected to the collector, the resistance of which at the time of start-up is maximum. As it decreases, the rotor current increases and the motor spins up. Such machines are called slip-ring motors. They are used in crane equipment and as traction motors for trolleybuses and trams.
- Reduce the voltage and currents supplied to the stator. In turn, this is implemented using:
a) autotransformer or rheostat;
b) key circuits based on thyristors or triacs.
It is the key circuits that are the basis for the construction of electrical devices, which are usually called soft starters or soft starters. Please note that frequency converters also allow you to smoothly start the motor, but they only compensate for a sharp increase in torque without limiting the starting current.
The principle of operation of the key circuit is based on the fact that the thyristors are unlocked for a certain time at the moment the sinusoid passes zero. Usually in that part of the phase when the voltage rises. Less often - when it falls. As a result, a pulsating voltage is recorded at the soft starter output, the shape of which is only approximately similar to a sinusoid. The amplitude of this curve increases as the time interval increases when the thyristor is turned on.
Soft starter selection criteria
In order of decreasing importance, the device selection criteria are arranged in the following sequence:
- Power.
- Number of controlled phases.
- Feedback.
- Functionality.
- Control method.
- Additional features.
Power
The main parameter of the soft starter is the value of I nom - the current strength for which the thyristors are designed. It should be several times greater than the value of the current passing through the motor winding, which has reached the rated speed. The multiplicity depends on the severity of the launch. If it is light - metal-cutting machines, fans, pumps, then the starting current is three times higher than the nominal one. Heavy starting is typical for drives with a significant moment of inertia. These are, for example, vertical conveyors, sawmills, presses. The current is five times higher than the rated current. There is also a particularly difficult start-up that accompanies the operation of piston pumps, centrifuges, band saws... Then I nom softstarter should be 8-10 times more.
The severity of the launch also affects the time it takes to complete. It can last from ten to forty seconds. During this time, the thyristors become very hot, as they dissipate part of the electrical power. To repeat, they need to cool down, and this takes as much as the working cycle. So if technological process requires frequent on-off, then choose a soft starter as for a hard start. Even if your device is not loaded and easily picks up speed.
Number of phases
One, two or three phases can be controlled. In the first case, the device more softens the increase in starting torque than current. The most commonly used two-phase starters. And for cases of heavy and especially heavy start-up - three-phase.
Feedback
SCP can work according to a given program - increase the voltage to the nominal value for the specified time. This is the simplest and most common solution. Availability feedback makes the management process more flexible. The parameters for it are the comparison of voltage and torque or the phase shift between the rotor and stator currents.
Functionality
Ability to work on acceleration or braking. The presence of an additional contactor that shunts the key circuit and allows it to cool down, and also eliminates phase asymmetry due to a violation of the shape of the sinusoid, which leads to overheating of the windings.
Control method
It can be analog, by rotating the potentiometers on the panel, and digital, using a digital microcontroller.
Additional functions
All types of protection, energy saving mode, the ability to start with a jerk, work at reduced speed (pseudo-frequency regulation).
Properly selected soft starter doubles the working life of electric motors, savesup to 30 percent electricity.
Why you need a soft starter (softstarter)
Increasingly, when starting the electric drives of pumps, fans, a soft starter (soft starter) is used. What is it connected with? In our article we will try to highlight this issue.
Induction motors have been in use for over a hundred years, and relatively little has changed in how they function. The launch of these devices and the problems associated with it are well known to their owners. Starting currents lead to voltage drops and wiring overloads, as a result of which:
some electrical equipment may spontaneously turn off;
possible hardware failure, etc.
A timely installed, purchased and connected softstarter allows you to avoid unnecessary spending of money and headaches.
What is starting current
The principle of operation of asynchronous motors is based on the phenomenon of electromagnetic induction. The build-up of reverse electromotive force (emf), which is created by applying a changing magnetic field during engine start, leads to transients in the electrical system. This transient may affect the power system and other equipment connected to it.
During starting, the motor accelerates to full speed. The duration of the initial transients depends on the design of the unit and the characteristics of the load. The starting torque should be the largest and the starting currents should be the smallest. The latter entail detrimental consequences for the unit itself, the power supply system and the equipment connected to it.
During the initial period, the starting current can reach five to eight times the full load current. During motor start, the cables are forced to carry more current than during the steady state period. The voltage drop in the system will also be much greater during start-up than during stable operation - this becomes especially evident when starting a large unit or a large number of electric motors at the same time.
Motor protection methods
As the use of electric motors became widespread, overcoming problems with starting them became a challenge. Over the years, several methods have been developed to solve these problems, each with its own advantages and limitations.
Recently, significant advances have been made in the use of electronics in the regulation of electric power for motors. Increasingly, when starting electric drives of pumps and fans, soft starters are used. The thing is that the device has a number of features.
A feature of the starter is that it smoothly applies voltage to the motor windings from zero to the nominal value, allowing the motor to smoothly accelerate to top speed. The mechanical moment developed by the electric motor is proportional to the square of the voltage applied to it.
During the start process, the soft starter gradually increases the applied voltage, and the electric motor accelerates to the rated speed without high torque and peak current surges.
Types of soft starters
To date, three types of soft starters are used for the smooth start of equipment: with one, two and with all controlled phases.
The first type is applied to single-phase motor to ensure reliable protection overload, overheating and reduce the effect of electromagnetic interference.
As a rule, the second type circuit, in addition to the semiconductor control board, includes a bypass contactor. After the motor has run up to rated speed, the bypass contactor is activated and provides direct voltage to the motor.
The three-phase type is the most optimal and technically advanced solution. It provides current and magnetic field strength limitation without phase distortions.
Why do you need a soft starter?
Due to the relatively low price, the popularity of soft starters is gaining momentum by modern market industrial and household appliances. Soft starter for an asynchronous electric motor is necessary to extend its service life. The big advantage of the softstarter is that the start-up is carried out with smooth acceleration, without jerks.
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Similar video reviews
Everyone knows how cool it is to have a well at home. It is convenient and effective until nothing breaks. And problems sooner or later will make themselves felt, and according to the law of meanness, at the most inopportune moment. Abandoning the well and digging a well is not an option. It is better to prevent possible accidents and protect yourself from them in advance.
Which water supply option is best for a private house
Water from the well is lifted by a special deep well pump. Depending on the design of the water supply, it is pumped into a special tank - a hydraulic accumulator or fed directly into the water supply.
The tank system is more suitable for a private house. For example, for a family of 3-4 people, an average of 70 liters per day is enough. For such water supply, you will need: a 50-liter accumulator for the corresponding volume, a pressure switch and a pump with a pumping speed of 1 m3 / h. All together will cost $100.
But, for a hotel with 12 rooms, this option is unprofitable, because you need a tank the size of a whole room. A 500-liter accumulator will cost $ 400 and will take up a lot of usable space. It is cheaper and more efficient to buy a frequency converter for $150-200.
Water supply with frequency converter
The frequency converter regulates the speed of the electric motor depending on the pressure in the water supply. It works like this principle:
- A pressure switch connected to a frequency converter is placed on the water pipe;
- The system is connected to the network and the frequency converter smoothly changes the characteristics of the pump current;
- Due to this he gradually reaches nominal speed;
- When filling in the pipes, the pressure increases, and the relay sends a signal to the frequency converter, which reduces the pumping speed.
What are the advantages of such a system?
User friendliness
For example, when a visitor in a hotel room takes a shower, the pressure in the plumbing drops and the pump runs faster. When the tap is turned on, the electric motor runs at low speed so that water does not drain from the pipes. So, if you unscrew the tap, it will instantly begin to flow under the required pressure.
Grid security
When turned on, each electric motor consumes 3-4 times more electricity - a starting current occurs. At this point, the network load is respectively 300-400% of the nominal. The peak lasts for a fraction of a second until the electric motor reaches normal speed. Why is it dangerous?
Let's go back to our hotel. To ensure that power outages do not leave visitors without the benefits of civilization, any responsible owner will install a generator. Suppose that the power of the backup source will be 20 kW, of which 10 kW will immediately go to lighting, air conditioners, sockets with laptops, etc.
The pump power is 5 kW, but since its starting current is 3 nominal, at the start it will take all 15 kW. The generator can only provide 10 kW, but this will not be enough for the electric motor. Such a load will disable the generator, and as a result, the hotel will remain without light and water.
A frequency converter removes starting current. If in the previous example there was a frequency converter, the load on the generator would not exceed 15 kW and it would work in safe mode.
Long pump life
Starting current harms not only the network, but also the electric motor. Each time it is turned on, it operates in abnormal mode and briefly withstands a load that it was not designed for. Sudden starts and stops increase the wear of the electric motor. The frequency converter makes soft stop than doubles the service life.
What happens if the water supply system is not protected?
In order for the water supply of the house to be uninterrupted and efficient, it still needs protection. Undoubtedly, the pump is the main element in the system, but no matter how expensive and high-quality it is, nothing will save it from a short circuit.
Accidents happen not only under water, but also in the submersible cable and even the network of the house. It's hard to predict what will break first. In order not to play the lottery, it is better to protect yourself from everything at once.
If you look at the submersible from a technical point of view, you have to agree that this is a very high-tech unit:
- with minor overall dimensions provides high performance;
- able to work for a long time in relatively difficult conditions.
The cost of a downhole pump is relatively high, installation in the casing string is difficult. The conclusion follows from this: a borehole pump is equipment that you need to try to repair and change as little as possible. And for this it is necessary to create optimal operating conditions for it, then the equipment will last as long as possible without breakdowns and failures.
Factors affecting the life of a well pump
Any electric motor (and a pump is, in fact, an electric motor) experiences maximum loads at the time of starting. The less often the engine is turned on, the longer it will last. That is why in the water supply scheme country house a storage tank is provided - simple or hydroaccumulator - so that the pump has time to pump as much water as possible in one cycle of operation.
In this case, the borehole pump will be activated in the operation of the water supply system only when the water level in the storage tank drops. In the absence of a water storage tank, the pump motor will start every time at least one draw-off point is activated.
The second negative factor is starting currents that are several times higher than the nominal ones. This is due to the inertia of the mechanical part of the electric motor, when the rotation of the components begins a little later than the power supply. With frequent starts pumping equipment and the constant occurrence of high starting currents, the protective function of the motor winding insulation gradually decreases due to high thermal loads. And this is already fraught with a short circuit and, as a result, a breakdown of the pump.
Ways to compensate for high inrush current
To reduce the starting current, it is necessary to provide for the installation of a soft start system. We bring to your attention two types of soft start systems for a borehole pump:
- Smooth SS-start using a special control panel for borehole pumps manufactured by domestic manufacturers (automatic control and protection stations for ACS "Kaskad" and "Vysota") and foreign (Pedrollo, Grundfos and some others).
- Starting the engine of a borehole pump using a frequency converter.
The principle of supplying power to the pump with the help of ACS electronic stations is an automatic gradual increase in voltage, regulated by phase control. By means of frequency conversion, the starting current is kept at the nominal level.
The main functions of the ACS:
- automatic (with the possibility of switching to manual mode) start and stop of the pump at the command of a relay that determines the water level in the storage tank;
- remote control of the pump;
- pump protection and power off in the event of a short circuit, phase imbalance and overloads;
- dry run protection.
The disadvantages of ACS include the high cost of equipment.
Do you know?
Some well pump manufacturers offer models with a built-in soft start system. For example, Grundfos SQ and SQE series.
"Why is it necessary to ensure a smooth start of a well pump", BC "POISK", tell friends: January 3rd, 2016
