Smooth start asynchronous engine - It is always a difficult task, because to start an induction motor requires high current and torque that can burn the winding of the electric motor. Engineers are constantly offered and implement interesting technical solutions To overcome this problem, for example, the use of the inclusion scheme, autotransformer, etc.
Currently, similar methods are applied in various industrial installations For uninterrupted operation of electric motors.
The principle of operation of the induction electric motor is known from physics, the whole essence of which is to use the difference between the frequencies of rotation of the magnetic fields of the stator and the rotor. The magnetic field of the rotor, trying to catch up with the magnetic field of the stator, contributes to the excitation of a large starting current. The motor operates at full speed, while the torque value is also increasing after the current. As a result, the aggregate winding may be damaged due to overheating.
Thus, the installation of a soft starter becomes necessary. The UPP for three-phase asynchronous motors allow you to protect the aggregates from the initial high current and the torque arising from the effect of the slip when the induction motor operation.
Advantageous features of applying a scheme with a smooth starter device (UPP):
There are five basic methods of smooth start.
Most schemes household appliances And electrical instruments were created on the basis of the collector electric motor 220 V. Such a demand is explained by universality. For units, powered from constant or alternating voltage. The advantage of the scheme is due to the provision of an efficient starting point.
To achieve a smoother start and have the ability to set the speed of rotation, revolutions are applied.
Starting the electric motor with your own hands can be done, for example, thus.
Published by the author - - November 8, 2013High starting current - a problem for systems with limiting maximum power. The machine can knock out the system uninterrupted power Get into overload mode. How to be?
A successful solution will be the use of a device of a smooth start (UPP). For example, we have a single-phase submersible 1kW power pump, located in the well at a depth of 50 meters. For the start of its engine, 4-6 multiple starting current will be required, i.e. The system must withstand short-term power around 5kW. For example, the inverter, calculated on 3kW, simply will not be able to start. The moment of the start will also be accompanied by a sharp increase in pressure, which actually means hydrocating through the water supply system.
In line, feeding the pump insert the UPP. The device for a specified time (usually up to 20 seconds) smoothly lifts the voltage, which will allow the pump with acceleration to promote the impeller, without a jerk. As a result, we equated the starting current to the nominal, i.e. It made up the amount of 1kW and significantly extended the life of the submersible pump (the service life increases somewhere 2 times, given the cost of the pump, the decision to use the UPP, even in the absence of a system of energy reservation becomes obvious):
Imagine a connection scheme that can be used both with single-phase and three-phase equipment:
Is there any restrictions to use a smooth starter? Yes, there are also about them to know:
1) UPP cannot be used with refrigerators. High starting current is necessary for breaking in the motion of the compressor valves
2) similarly for air conditioners and other equipment
If you have any questions, I will be happy to answer in the comments!
There are many reasons for the inclusion of household pumps through a smooth starter.
Usually, the submersible or surface pump is connected via an electromechanical or electronic relay, an automation unit or a magnetic starter. In all listed cases, the mains voltage is supplied to the pump by closing the contacts, that is, through a direct connection. This means that on the windings of the electric motor stator, we feed the full network voltage, and the rotor at this time does not rotate. This leads to the appearance of an instantaneous powerful rotational torque on the rotor of the pump electric motor.
Such a connection scheme is characterized by the following phenomena when the pump is started:
Racing current through the stator (respectively, through the supply wires), as the rotor is short-circuit.
In a simplified understanding, we have a short circuit on the secondary winding of the transformer. According to our experience, depending on the pump, manufacturer and load on the shaft, the pulse trigger can exceed the operating current from 4 to 8, and on separate copies and up to 12 times.
The sharp appearance of the torque on the shaft.
This has a negative impact on the launcher and working winding of the stator, bearings, ceramic and rubber seals, significantly increasing their wear and reducing the service resource.
The appearance of a sharp torque on the shaft leads to a sharp rotation of the well pump housing relative to the pipeline system.
We have repeatedly visited how because of this, the well pump disconnected from pipelines and fell into a well. In the case of a pumping station based on surface pumpMounted on the hydroaccumulator platform, this leads to the breaking of fastening nuts and the destruction of the welded points and the seams of the hydroaccumulator. Also, with direct inclusion of the pump, the service life of the plumbing and shut-off reinforcement is reduced, especially in the places of their compound.
It is believed that the hydroaccumulator removes the hydroedar in the water supply system.
This is true, but the hydrowoods disappear in pipelines only starting from the connection site of the hydroaccumulator. In the interval between the pump and the hydroaccumulator, with direct connection of the hydrophole pump, it remains. As a result, on the interval from the pump to the hydroaccumulator, we have all the consequences of the hydraulic man on all parts of the pump and the pipeline system.
In water filtration systems, hydroudars arising from directly connecting the pump significantly reduce the service life of the filter elements.
If the local power grid weakThe launch of the pump with a power of more than 1 kW with direct connection will also learn your neighbors on a sharp discharge voltage in the network at the time of the pump is turned on.
If the local network Extremely weakand your neighbor also enjoys life by connecting all available to the network electrical devices, then the well pump immersed on a big depth may not start. This voltage jump can output electronic devices connected to the network. Cases are known when when the pump started, a costly refrigerator was faced.
The more often the pump is turned on, the smaller its resource service.
Frequent launches Through direct connection lead to the failure of plastic couplings of well pumps connecting the electric motor with the pumping part.
We and I went on the problems that occur when the pump is launched without smooth starters (UPP).
It should be noted that when the pump is turned off without UPP With a straight circuit connected negative moments:
When the pump is turned off, it is also hidden in the system, but now due to a sharp reduction in the torque on the pump shaft, which is equivalent to creating instant discharge.
A sharp decrease in the torque on the pump shaft also leads to the rotation of the pump housing, but in the opposite direction.
Recall the pipelines and threaded pump connections.
In conventional household pumps, electric motors are asynchronous and have a clearly expressed inductive character.
If we dramatically interrupt the flow of current through the inductive load, the voltage jump occurs on this load due to the continuity of the current. Yes, we blur contact, and all the high voltage should remain on the pump side. But with any mechanical blurring of contact, there is a so-called "rattling of contacts", and high voltage pulses fall into the network, which means both in the instruments connected at this time to the network.
Thus, with a direct connection of the pump, an increased wear of the mechanical and electrical parts of the pump occurs (both at start-up and when disabling). Also suffer the devices included in the same network, and the resource of the operation of filtering and water fittings is reduced.
Using smooth starters ("Aquacuation UPP-2.2C") Allows you to smooth out most of the shortcomings described above. In the device UPP-2.2S A specially calculated increase in the voltage increase in the pump is implemented, which allows you to start the pump in the most unfavorable operating conditions on the one hand, and on the other hand, it smoothly increase the rates of rotation of the shaft. Also in this device is built-in protection against low and high-voltage networks to protect the pump from extreme modes of operation and inclusion.
IN UPP-2.2S Used phase symistor control. At the time of start-up, a part of the network voltage is served, which creates a rotating moment, sufficient for the guaranteed launch of the pump. As the rotor promotes, the voltage on the pump is smoothly increasing until the voltage is complete. After that, the relay turns on and the simistor is turned off. As a result, when used UPP-2.2S The pump is connected to the network through the contacts of the relay, that is, the same as with a direct connection. But for 3.2 seconds (this is a smooth start time) a pump voltage is supplied through a simistor, which provides a "soft start", without sparks on the relay contacts.
With this launch, the maximum starting current exceeds the worker not more than 2.0-2.5 times instead of 5-8 times. Using UPP-2.2SWe are 2.5-3 times to reduce the launchers on the pump and extend the life of the pump to the same time, we provide more comfortable operation of devices connected to the electrical network. UPP-2.2S You can call the device with resource-saving technology.
