Common faults and maintenance methods of the hotte

2022-08-12
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Common faults and maintenance methods of jqlx series motors

domestic 55 inch and 46 inch dual-mode vulcanizers mostly use jqlx series three-phase asynchronous motors produced in Shunde, Guangdong. This series of motors have high starting torque and are equipped with DC disc electromagnetic brakes. It is specially made for supporting tire curing machine

in addition to the working principle of ordinary three-phase asynchronous motors, the difference of this series of motors is to add a set of DC disc electromagnetic brakes

the working principle of disc electromagnetic brake is: the working quota of the brake is consistent with that of the motor. The brake uses an external DC power supply. When the motor is connected to the current, the brake coil should be energized at the same time. The electromagnet immediately attracts the armature and compresses the spring embedded in the electromagnet to separate the brake part from the armature and the friction plate. The brake part rotates with the toothed shaft sleeve and the rotor. If the motor cuts off the power supply, the brake should also cut off the positive pressure and lateral force by controlling the loading. The electromagnet loses its electromagnetic suction, and the spring immediately pushes the armature to compress the brake parts to produce friction torque, which will immediately brake the motor rotor

the following is a brief description of the fault phenomena often encountered in the production process of this series of motors and their solutions

1 common faults and maintenance methods of jqlx series motors

1.1 the motor does not operate after being powered on

this fault should be considered from the following aspects:

(1) check the power supply voltage value. When the voltage entering the motor junction box is less than 90% of the rated voltage, the motor cannot be started

(2 high and low temperature alternating test box and high and low temperature alternating damp heat test box have requirements for temperature change speed) check whether the brake contactor and the main motor contactor are closed at the same time. The synchronization of the actions of the two contactors must be ensured, otherwise the motor is in the braking state

(3) measure the DC output voltage when both the motor contactor and the brake contactor are closed

(4) when the above conditions (3) are met, check the air gap between the electromagnet and the armature with a feeler gauge. When the air gap is greater than 2mm, it will cause the working length of the spring to increase. Under the same magnetic potential, the magnetic density of the air gap will be significantly reduced. The new advanced manufacturing plant of dnipeg in Suzhou, China will be officially put into operation, and in serious cases (greater than 2mm), the armature will not be able to attract. Generally, the air gap size should be less than 1.5mm

(5) when (3) and (4) conditions are met, there is a local short circuit inside the brake coil, so that the electromagnet magnetic force cannot attract the armature, and the motor is still in the braking state

1.2 the motor runs in the vertical position of the upper model, and the displacement is large after braking.

after finding this phenomenon, the gap between the electromagnet and the armature should be adjusted in time to ensure that the decline of the upper beam of the machine after braking is not more than 15mm. If the friction plate is seriously worn, it needs to be replaced to ensure the reliability and safety of braking

1.3 after the motor is connected to the three-phase power supply, the air switch trips

(1) measure the insulation resistance of the three-phase winding of the motor to the housing with a 500V megger. If the resistance value is lower than 0.5m Ω, the motor must be dried. It can not be put into use until it meets the specified requirements

(2) if (1) is excluded, open the common end of the motor star connection method, and measure the six taps one by one with a 500V megger. Check the insulation resistance between two phases. If there is a short circuit between phases, fault 1.3 will occur

1.4 after the motor is connected to the starting power supply, it makes a buzzing sound and the speed is slow.

this phenomenon is generally caused by phase loss. The following aspects should be checked

(1) first check whether the fuse is blown

(2) control whether the three-phase contacts of the motor contactor are closed at the same time

(3) use a 500V megger to check whether the three-phase winding of the motor is open circuit

(4) check the screw contact of the connecting wires of various devices between the three-phase power supply and the motor junction box (there is oxide, oil dirt at the wire joint or the connecting screws are not tightened)

1.5 the current value of the motor is much higher than the rated current during the mold opening and closing operation, or points to infinity as soon as it is started, but the motor does not operate

(1) if the current suddenly points to infinity when it is close to the lowest point during the mold closing process, there are generally the following two factors

① the operator adjusted the molding pressure in the capsule too high during the molding process, causing the load to increase and the current to surge

② other valves (primary water, secondary water, internal cooling water) that convey media to the capsule leak, causing the pressure in the capsule to increase, resulting in a surge in current and unable to continue mold closing

(2) if the running current of the motor at any position is relatively high, the following two factors should be checked

① check the lubricating oil in the reducer. If there is too little lubricating oil, water is mixed in the oil, or the oil has been emulsified and deteriorated, the running current of the motor will increase. The lubricating oil should be replenished, the water should be drained, and the deteriorated lubricating oil should be replaced

② the motor rotor cage bar fracture will also increase the motor current. If it is not handled in time, it will accelerate the fracture of other cage bars, and the motor will be burned over time. Generally, cage bar fracture can be treated by welding

③ there is also a phenomenon that the mechanical transmission parts are stuck, which also increases the motor current

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