# Detection and removal of common faults in motor

Update:2017-08-09

There are two kinds of motor faults, mechanical and electrical. The mechanical faults are easy to find, and the electrical faults must be analyzed and judged by measuring their voltage or current. We now introduce the inspection and removal of common faults in motors.
One. the no-load current of the motor is large
The multimeter in DC 20A gear, the red and black pen are connected to a power source input controller. Turn on the power and record the maximum current value of the meter at the time the motor does not rotate. A1. Turn the handle and turn the motor at high speed without load. It is more than 10s. After the speed of the motor is stable, begin to observe and record the maximum value of the meter at this time A2. The no-load current of motor =A2-A1
The maximum no-load no-load current reference of various motors is as follows:
Ammeter，When the no-load current of the motor is greater than the limit data of the reference table, it shows that the motor is out of order. The reason why the no-load current of motor is large is:
The internal friction of motor is large.
Local short circuit of coil.
Demagnetization of magnetic steel.
two、The no-load / load speed ratio of the motor is greater than 1.5
Turn on the power, turn the handle, make the motor rotate at high speed and no load, more than 10s. When the speed of the motor is stable, the maximum speed of the motor is measured at N1 with a hand-held speed / speed meter.
In the standard test conditions, traveling above 200m distance, began to measure the maximum load speed of motor N2. Load / no-load speed ratio of =N2 / N1
When the motor no-load speed / load ratio is greater than 1.5, indicating the motor magnet demagnetization has been quite severe, should replace the motor set inside the magnet, in the process of practical maintenance of electric vehicles in general is the replacement of the entire motor.
Three 、 motor heating
Using the non-contact infrared thermometer, or universal temperature measuring meter gear (with temperature measurement multimeter), measurement of motor cover temperature exceeds the ambient temperature is 25 degrees above, that has exceeded the normal range the temperature rise of the motor, should be 20 degrees below the general motor temperature rise.
The direct cause of the heating of the motor is caused by a great current. Motor current I, input electric potential E1 motor, sense of rotation of the motor electromotive force (also called back EMF) E2, and the relationship between the motor coil resistance of R is: I= (E1-E2), R
I increases, indicating that R becomes smaller or E2 decreases. R becomes smaller, usually caused by short circuit or open circuit. The reduction of E2 is generally caused by demagnetization of magnetic steel or caused by short circuit or open circuit of the coil.
In the practice of electric vehicle maintenance, the method to deal with the motor heating failure is to replace the motor.
Four、 The motor has mechanical collision or mechanical noise when it is running
No matter the high speed motor or the low speed motor, there should be no mechanical collision or discontinuous and irregular mechanical noise in the running of the load. Different forms of motors can be referred to the above table for maintenance in different ways.
Five、 the vehicle mileage is shortened, the motor is weak
When the environment temperature is 25 degrees centigrade, under the standard test conditions, the total mileage of the vehicle assembled with different types of motors is not the same. We can refer to the data in the following table to determine whether the mileage of the vehicle is normal or not. The data in the table is new when the battery is full and the new motor with the run out of the actual mileage number 60%, if the number of actual driving mileage is less than the reference number, we can determine the vehicle mileage short.
The performance of motor vehicle fatigue is small, the starting time is long, and the speed of driving test is slowed down obviously.
Vehicle continued mileage short and motor fatigue (commonly known as motor boring) reasons are more complex. However, after we have ruled out the above 4 kinds of motor failure, generally speaking, the vehicle continued mileage short fault is not caused by the motor. This is related to the attenuation of the battery capacity, the charger charging the battery, the controller parameter drift (the PWM signal does not reach 100%) and so on. These problems are introduced in the following related chapters.
Six、brushless motor phase
The absence of phase in brushless motor is caused by the damage of the hall element of brushless motor. By measuring the resistance of the output of the hall element relative to the hall wire and the lead of the relative hall power source, the comparison method is used to determine which Hall element is faulty.
In order to ensure the commutation position of the motor, it is generally recommended to replace all three of the hall elements at the same time. Before replacing the hall element, it is necessary to make sure that the phase algebra angle of the motor is 120 degrees or 60 degrees, and that the three Hall elements of the phase angle motor are in parallel with each other in 60 parallel positions. While the 120 DEG angle motor, a Hall element in the middle of the three Hall elements is placed in the position of 180 degrees of reversal.