Advantages of a Permanent Magnet Contactor

Figure 1: A Permanent Magnet Contactor for Power Distribution.

The permanent magnet contactor is a new type of low-voltage switchgear. Using the working principle of electromagnetic operation and permanent magnet holding, it overcomes the shortcomings of traditional electromagnetic contactors such as large energy consumption, large working noise, and large influence by grid voltage, and has a good energy-saving effect.
Advantages of a permanent magnet contactor, especially alternating current (AC) one, will be presented in detail as follows.

1. Energy Saving

The closing maintenance of traditional AC contactors must be achieved by the continuous energization of the coil, and the current ranges from tens to thousands of milliamps. The permanent magnet AC contactor's closing relies on the permanent magnet force, instead of the electromagnetic force generated by the current through the coil. The only current it uses is the 0.8~1.5mA working current of the electronic module. Therefore, it can save electricity to the greatest extent, and the electricity saving rate is as high as 99.8%.

2. No Noise

The closing maintenance of the traditional AC contactor is achieved by energizing the coil to generate electromagnetic force on the silicon steel sheet, which makes the moving and fixed silicon steel sheets to be attracted. When the grid voltage is insufficient or the surface of the silicon steel sheets are uneven or have dust, foreign objects, etc., noise will be generated; while the closing maintenance of the permanent magnet AC contactor is achieved by the permanent magnet force, so there will be no noise.

3. No Temperature Rise

Traditional contactors rely on energizing the coil to generate enough electromagnetic force to keep attraction. The coil is composed of resistance and inductance, and long-term current flow will inevitably generate heat. The magnetic flux in the iron core also generates heat. These two kinds of heat work together in the contactor cavity, often causing the contactor coil to burn out. In addition, heat generation reduces the main contact capacity.
The permanent magnet AC contactor, in contrast, is maintained by permanent magnet force. Without maintaining the coil, naturally there is no temperature rise.

Figure 2: A wiring permanent magnet latching lighting contactor.

4. Long Service Life, High Reliability

The service life and reliability of the contactor are mainly determined by that of the coil and contact. When the traditional AC contactor works, the coil and the iron core will heat up, especially when the voltage, current and magnetic gap increase. The permanent magnet AC contactor does not have the possibility of burning the coil.
Contact ablation is mainly caused by the arc generated during opening and closing. Compared with the traditional contactor, the permanent magnet AC contactor has the effect of not only the electromagnetic force but also the permanent magnet force when closing, so the closing speed is much faster than that of the traditional AC contactor, which significantly avoids the occurrence of arc.

5. No Electromagnetic Interference

The permanent magnet circuit used by the permanent magnet AC contactor is completely sealed, and will not be subjected to external electromagnetic interference during use, nor produce such interference.

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