Most home and office devices are powered by a single-phase voltage of 230 V. However, in a home or company, we will also encounter a number of three-phase receivers. An example of these are three-phase induction motors. They use all three phases to operate. The case of such an installation is more complicated, so additional control relays are needed. One of them is a phase asymmetry sensor and a phase sequence sensor with a voltage asymmetry threshold setting. Why is such a device so important, what does it measure and where is it used? You will learn all this by reading the article below. We invite you to read it.
What is a phase asymmetry sensor?
Alternating current is transmitted via the power grid. This means that its characteristics, including voltage, change sinusoidally over time. Due to this feature, it is possible to connect three-phase induction motors to the grid. Each phase reaches its maximum voltage at a different time (1/3 phase shift). This affects the shape of the magnetic field generated in the motor. Unfortunately, power grids are not ideal, and the electrical energy transported through them has a course that differs from the ideal one. The phase asymmetry sensor is designed to detect voltage drops on a single phase, which causes a difference (asymmetry) in the effective voltage value on different phases. Voltage asymmetry in the case of power supply of three-phase motors is a very serious threat to the entire drive system. An equally dangerous phenomenon is a change in the phase sequence causing the motor to operate in reverse.
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How does a phase asymmetry sensor work?
Monitoring relays perform current measurements of network parameters. Their result is often visible in the form of illuminated information diodes. Very often, the occurrence of a problem immediately causes the power contactor to disconnect. This type of protection allows the motors to be switched off before any failure occurs.
In the case of a phase asymmetry sensor, the voltage on each of the three wires is measured. If a drop exceeding 55 V is detected on one line, the contactor is immediately disconnected. In the company's relays Zamel There are also additional outputs for activating an audible or light signal. This way, the operator immediately knows what the reason is for the engine stopping.
Where are phase asymmetry sensors used?
The use of this type of Zamel control relays only makes sense in three-phase installations. A sensor for individual phases can sometimes be found in the electrical switchboard. Phase sequence protection is also a basic feature of three-phase electric motors. This is due to the fact that changes in the current characteristics in such cases generate undesirable forces that act in the opposite direction to the motor rotation. When started, the motor may start to rotate in the opposite direction. The effects of such action may be disastrous!
For this reason phase asymmetry sensor is installed on each three-phase electric motor. If an irregularity is detected, the contactor immediately disconnects the drive from the voltage, which is intended to protect it from damage. Moreover, the motor should remain normally disconnected - this means that a failure of the phase sequence sensor will prevent the device from restarting until this protection is replaced.
What to look for when choosing the right phase asymmetry sensor?
Buying the right engine protection is a very important issue. What to look for when choosing the optimal model?
- Sensor parameters. Check the intensity and power at which a given model can operate.
- Additional information signals. Does the relay have a light signal? Maybe you can connect an audible signal to inform about power supply problems.
- Quality of workmanship. It is worth choosing among well-known and recognizable manufacturers (such as Zamel), who are valued for the quality of the electrical components they sell.
- Device size - it will be mounted in a switchboard. It is worth considering how much space will be needed for a specific phase asymmetry sensor model.
When making a purchase, pay attention to the details listed so that it does not turn out that the protection does not work on the day of the test. The cost of a good sensor is much lower than the bill for the later repair of the engine and devices connected to it. Therefore, it is not worth saving.
The Zamel phase asymmetry sensor can be found in the Onninen wholesaler
Protecting your installation from accidental overvoltages and unwanted phase asymmetry is very important. That is why you can now also find the Zamel phase asymmetry sensor in our store. We have also prepared other control relays for you that will ensure the correct operation of your devices. If you do not know which ones you should use, contact us. We will be happy to advise you on what protection will allow you to sleep peacefully.