Most home and office devices are powered by single-phase 230 V. However, in your home or company you will also find a number of three-phase receivers. Their example are three-phase induction motors. They use all three phases to function. The case of such an installation is more complicated, so additional control relays are needed. One of them is a phase unbalance sensor and a phase sequence sensor with a voltage unbalance threshold setting. Why is such a device so important, what does it measure and where is it used? You will learn about all this by reading the article below. We invite you to read.
What is a phase unbalance 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 network. 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 engine. Unfortunately, power grids are not perfect, and the electricity transported through them is different from ideal. The phase unbalance 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 powering 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 engine to operate in reverse.
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How does the phase asymmetry sensor work?
Control relays perform current measurements of network parameters. Their result is often visible in the form of lit information diodes. Very often, when a problem occurs, the power contactor immediately disconnects. This type of protection allows the engines to be turned off before any failure occurs.
In the case of a phase unbalance 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 a sound or light signal. This way, the staff immediately knows the reason for the engine stalling.
Where are phase asymmetry sensors used?
The use of this type of Zamel control relays only makes sense in three-phase installations. The sensor for individual phases can sometimes be found in the electrical switchboard. Phase sequence protection is also the basic equipment of three-phase electric motors. This is due to the fact that the change in current characteristics in such a case creates undesirable forces acting in the opposite direction to the motor rotation. When starting, the motor may start to rotate in the opposite direction. The consequences of such action may be disastrous!
For this reason phase asymmetry sensor is installed on every three-phase electric motor. If an irregularity is detected, the contactor immediately disconnects the drive from the voltage to protect it against damage. Furthermore, the motor should remain normally disconnected - this means that a phase sequence sensor failure will prevent the unit from restarting until this protection is replaced.
What should you pay attention to when choosing the right phase asymmetry sensor?
Purchasing the right engine protection is a very important issue. What should you pay attention to when choosing the optimal model?
- Sensor parameters. Check the intensity and power with which a given model can operate.
- Additional information signals. Does the relay have traffic lights? Maybe you could connect an audible signal to let you know if there are power problems.
- Production quality. It is worth choosing from well-known and recognizable manufacturers (such as Zamel), who are valued for the quality of the electrical components they sell.
- Size of the device - it will be mounted in the distribution box. It is worth considering how much space will be needed for a specific model of phase asymmetry sensor.
When making a purchase, pay attention to the details mentioned so that it does not turn out that the protection will not work on the test day. The cost of a good sensor is much lower than the bill for subsequent 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 against accidental overvoltages and undesirable phase asymmetry is very important. That's 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 proper operation of your devices. If you don't know which of them you should use, please contact us. We will be happy to advise you on what security measures will allow you to sleep soundly.