1. Home
  2. Knowhow

A brief discussion on the analysis and treatment of common faults of ship motors

Date:2023-09-06   Author:XINDA MOTOR


There are thousands of large and small ship motors, which are distributed in different positions and play an important role, such as: steering gear, adjustable propeller, main engine fuel supply pump, main engine sea water cooling pump, auxiliary engine sea water cooling pump, crew The cabin air supply, return fan, side thruster, fire pump, etc. all have marine motors.

Whether its operation is normal or not directly affects whether the equipment can work normally and affects the safety of the ship's navigation. From this we can see that the ship's motor plays an important role in a giant ship of tens of thousands of tons.

The article mainly discusses the analysis and treatment of several common faults of marine motors based on years of work experience.

1. Common faults of ship motors and their solutions

Ship motors generally work full-time, and many motors work in humid and vibrating harsh environments for many years. Ship motor failures often occur, seriously affecting ship operations and crew daily life.

In use, marine motors will have various problems, such as motor bearing burnt due to lack of oil, motor winding burnt due to lack of phase, and motor insulation aging resulting in winding short circuit and other faults are relatively common. Now we analyze the causes and treatment methods for common faults .

1. Ship motor winding ground fault

As the ship sails on the water surface for a long time, the working environment of the ship motor is humid and harsh, and the ship shakes seriously, so the grounding fault of the ship motor winding often occurs in the ship motor.
According to many years of experience of technicians, the main reasons for this failure are as follows.

(1) The insulation of the motor windings is reduced due to moisture;
(2) The motor generates heat due to long-term overload and the insulation ages;
(3) The secondary assembly winding of the motor contacts the front and rear end covers of the motor;
(4) The bearing of the motor is damaged, causing the rotor to sweep and damage the insulation.

The method to solve this type of fault is to first check to determine whether the winding is affected by moisture or water droplets splash into it, causing insulation failure. If so, the motor should be disassembled and dried first. After the preliminary treatment, the motor temperature returns to normal ( Generally around 70°C), perform a secondary varnish treatment and then dry it; check whether the motor is overloaded. If the overload heat causes the insulation to age and the rotor to be damaged due to sweeping, the winding or grounding point should be re-insulated. , dip it in paint, and then dry it; this fault may also be caused by a grounding phenomenon in the motor assembly. At this time, it should be reassembled to insulate it from the front and rear end covers of the motor or add insulating paper.

After completing the above methods, the insulation meter should be used to measure the insulation of the repaired motor. It can only be put into use after it meets the insulation-related technical requirements.

2. The ship motor overheats or smokes during use.

The ship motor, like other motors, is the prime mover of electric drag. It often causes the motor to overheat or even smoke due to various factors. At this time, the motor should be stopped immediately and a fault analysis should be performed on the motor. Common The reasons for the failure are as follows.

(1) It may be that the motor bearing is damaged, causing the stator and rotor to heat up due to friction;
(2) The motor voltage is too high, and the core heat is greatly increased;
(3) The voltage of the motor is too low, the winding current increases and heats up,
(4) The motor runs without phase,
(5) The motor cooling fan is damaged;
(6) The stator winding is grounded.

There are several ways to solve this kind of failure.

(1) Replace the bearings and check the rotor alignment;
(2) Reduce the voltage, if there is a wrong connection of the motor, it should be corrected;
(3) Increase the power supply voltage or replace the power cord with a slightly larger diameter as appropriate;
(4) Measure the power supply voltage and restore three-phase power supply;
(5) Replace the motor fan, and check whether the air duct is blocked by foreign objects,
(6) Measure and check the winding and eliminate the fault.

3. The motor vibrates greatly and makes a buzzing sound during the sailing of the ship

When the ship is sailing, if a motor vibrates greatly and makes a buzzing sound, the faulty water pump should be powered off.

Then open the junction box, check the insulation of the line, and find out the cause of the fault.

Eliminate the fault, restore the normal function of the motor, and test the insulation again.

The main reason for this type of failure is that the three-phase asynchronous motor becomes a single-phase motor after a power line is broken.

The alternating pulsed magnetic field is generated in the stator and rotor air gap, which can be decomposed into two counter-rotating rotating magnetic fields.

If a power cord is disconnected when starting the motor, the two rotating magnetic fields act on the rotor respectively to produce two torques in opposite directions, and the torques are equal in magnitude.

Therefore, their effects cancel each other out, and the resulting torque is zero, so the rotor cannot start by itself, and only humming can be heard.

At this time, the current is very large, and after a long time, the motor will burn out; and if a wire is broken during operation, the torque along the direction of rotation generated by the two rotating magnetic fields will exceed the reverse torque, and the motor will still continue to operate. Turn.

If the rated load is still driven at this time, the rated current is bound to be exceeded.
Over time, the motor will also burn out.

4. Single-phase capacitor starting motor fault diagnosis

(1) The motor cannot start

If the motor rotor is rotated in any direction by force, the motor can start running in that direction. This is usually an open circuit of the auxiliary winding; poor contact of the centrifugal switch; or an open circuit of the capacitor.

If the motor rotor is rotated in any direction by force, and the motor speed rises to a certain value, then drops, and then rises again, sometimes faster and sometimes slower, it is generally an open circuit of the main winding coil.

At this time, attention should be paid to cut off the power supply immediately to prevent the winding from being energized and burned for a long time.
If there is a buzzing sound and the rotor is difficult to turn by hand, it is mostly mechanically stuck.
If it runs normally after removing the load, it may be caused by overload.

(2) The motor heats up quickly after starting

The cause of the fault is motor overload or mechanical friction (friction between the rotor and the stator); short circuit between turns of the main winding or short circuit to the casing; the starting switch does not operate, and the secondary winding keeps working and generating heat; there are coils in the main winding that are connected reversely; The auxiliary winding is wrongly connected, and the auxiliary winding is used as the main winding, especially for the motor that has just been repaired.

2. Inspection methods of ship motors during operation

Ship motors may cause different faults due to various reasons during operation. Personnel on duty can promptly and accurately determine the fault point of the ship motor and take effective and timely measures to eliminate the fault, which can effectively avoid further expansion of the ship motor fault. .

The fault finding of marine motors can be carried out according to "asking, looking, smelling, listening, and touching".

(1) "Ask":

Mainly by asking the personnel on duty whether there are any abnormalities in the operation of the ship's motor, whether there is a sudden increase or decrease in current, etc., and based on the abnormal phenomena in the operation of the ship's motor, the fault point of the motor is initially determined.

(2) "Look":

After arriving at the scene, first observe whether there are any obvious traces of water or damage from heavy objects on the ship's motor itself, so as to determine whether there are peripheral reasons for the motor failure.

(3) "smell":

Determine whether the motor is working in a normal state by smelling the odor around the motor. The motor will not produce any odor under normal working conditions. If you find any odor around the motor during inspection, stop the motor immediately for inspection.
For example, if the motor emits a burnt smell during operation, it may be caused by the insulating paint of the motor melting due to heat. Measures should be taken immediately to eliminate the fault and avoid the expansion of the motor fault.

(4) "Listen":

During the inspection and inspection, use copper listening rods to listen to the sound changes from the front and rear bearings of the motor and the motor body to determine whether the motor is working in a normal state.
If the motor emits a uniform and small "whistle" sound without any sudden high or low changes, it means the motor is working normally.
If there is abnormal noise, it means that the motor is faulty, and it needs to be stopped immediately for inspection to find out the fault point and eliminate it.

(5) "Touch":

You can judge whether the operating temperature of the motor is normal by touching the uncharged part of the ship motor with your hand. The temperature of the motor will rise when the motor is working normally, and the temperature of its body will also rise accordingly. If your hand touches the motor shell and it feels very hot, stop it immediately Carry out inspections, such as using a crank to judge whether the size of the load and whether the mechanical transmission is working normally, use a multimeter to measure whether the power supply voltage meets the requirements, and so on.

3. Conclusion

Ship motors are closely related to ship safety and the work and life of crews. However, ship motor failures occur one after another due to various factors. Generally, ship motors will have various perceptible precursors before various failures occur. When there are precursors to ship motor failure, , take timely and effective measures to solve faults, avoid unnecessary property losses, and improve the operational safety of ship power grids.

When the motor fails, it is necessary to find out the cause of the fault in a timely and accurate manner according to the specific fault phenomenon, locate the fault point, and quickly eliminate the fault to restore the normal operation of the motor. Significance.