Considerations and precautions in selecting explosion-proof motor

The following three main factors should be considered when selecting explosion-proof motor.

1. After the voltage, frequency and speed are determined, according to the load dragged by the motor and the power supply network, the over-installation coefficient k is selected to determine the motor power.

2. Confirm whether the technical indicators meet the requirements (to be finalized by both parties in the technical agreement). For the wound rotor motor, in order to select the matching starting and speed regulating system, the supplier also needs to provide the values of rotor voltage U2 and current I2.

3, according to the use environment to determine the protection level and explosion-proof type, explosion-proof level or corrosion protection category, level, and other requirements, such as outdoor, marine, etc. Reference: temperature group of explosion-proof motor and explosion-proof category.

Pay attention to the following three points when selecting explosion-proof motor.

1. The flame-proof grade of flame-proof motor can meet the requirements of flammable and explosive environment. Don't choose the one with high grade. 　

2. Determine the technical indicators according to the actual use situation. The higher the η and cos φ in the technical indicators, the better, saving electricity, while the other indicators are not. For example, the Tst of the motor driving the axial-flow pump and fan can be within the range of 0.6~0.8, and the Tm need not be high, and about 1.6 can meet the use requirements. If the buyer is a little loose on these two indicators, the designer can supplement the surplus functions dug out from here to Ist, that is, to reduce Ist. This is of great practical significance to the use places with small network capacity. Most of the loads of the two-pole motor are fans and pumps, so Tst is unnecessary. If the manufacturer pursues this index too much, the upper half of the groove shape of the cast aluminum rotor is designed to be very narrow, which increases the unnecessary difficulty in manufacturing; There are also many faults caused by broken strips and thin strips in use.

3, the protction level should be chosen moderately. The difference between IP54 and IP44 is mainly in the dustproof function. In order to save money, some buyers choose IP44 motor in the place where IP54 should be used, so that the motor bearing is damaged prematurely. On the other hand, when IP44 can meet the use requirements, it is unnecessary to choose P54. The latter should be equipped with rubber sealing ring, which is not as good as the former in maintenance.

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