Drum motor burnout is commonly associated with prolonged overloading, poor heat dissipation, abnormal power supply, phase loss, insulation deterioration, and frequent starts and stops. These conditions can cause the motor winding temperature to rise continuously. Over time, the insulation may deteriorate, eventually leading to winding short circuits or insulation breakdown and motor failure.
When troubleshooting a burnt-out motor, consider the operating load, power supply, working environment, and protection devices. A burnt winding does not necessarily indicate a manufacturing defect in the motor itself.
Prolonged Overloading
Continuous operation beyond the rated load is one of the common causes of motor overheating and winding burnout.
Load exceeding the rated capacity
When the weight or volume of conveyed material, or the operating resistance of the conveyor, exceeds the design requirements, the motor may need to produce more torque, resulting in increased operating current. If the motor remains overloaded for an extended period, winding copper losses increase and the temperature continues to rise. This can accelerate insulation aging and eventually cause winding damage.
Excessive mechanical resistance
Apart from excessive material loading, other mechanical problems can increase the motor load. These include excessive belt tension, idlers or bearings that do not rotate freely, and jamming in the internal reduction gearbox.
Even when the conveyed material does not exceed the rated capacity, excessive mechanical resistance can still cause motor overload.
Incorrect motor selection
If the rated power, output torque, or duty rating of the drum motor is insufficient for the actual conveying requirements, the motor may operate beyond its design limits, particularly during startup or prolonged operation.
Motor selection should take account of conveying capacity, belt speed, drum diameter, starting load, and operating time.
Poor Heat Dissipation
A motor generates heat during operation. Its cooling structure must transfer this heat away from the motor. If heat dissipation is inadequate, the winding temperature may exceed the permitted limit and accelerate insulation deterioration.
Restricted external heat dissipation
Dust, coal dust, and other debris accumulating on the drum surface may affect heat dissipation. Installation in a high-temperature environment or an area with poor ventilation can also reduce the equipment's ability to release heat.
Internal cooling system failure
Some drum motors use dedicated internal cooling structures or cooling fans. If these components fail or the cooling passages become blocked, heat may accumulate inside the unit.
Not all drum motors are equipped with separate cooling fans. Some oil-filled drum motors rely mainly on internal oil to transfer heat, which is then dissipated through the drum shell and other structural components. The cooling arrangement should therefore be checked according to the specific model.
Excessively high ambient temperature
At high ambient temperatures, the temperature difference between the drum motor and its surroundings becomes smaller, which can reduce heat dissipation. Prolonged operation under high-load conditions in a hot environment increases the risk of excessive motor temperature.
Abnormal Supply Voltage
A supply voltage outside the motor's rated operating range can also cause overheating, abnormal operation, and winding damage.
Overvoltage
If the supply voltage remains above the motor's permitted range, the motor's magnetic circuit may operate abnormally, increasing iron losses and winding temperature. In some cases, voltage surges can also place additional electrical stress on the winding insulation system.
Undervoltage
Low supply voltage can reduce motor starting torque and extend the starting time. Under a constant load, the motor may draw more current in an attempt to maintain the required operating torque, increasing winding heat.
Three-phase voltage imbalance
For a three-phase drum motor, a significant voltage imbalance can cause uneven phase currents and excessive temperature rise in individual windings. Even a relatively small difference in the measured supply voltages should not be ignored, as it can affect motor current and temperature.
During troubleshooting, measure the three-phase supply voltage and operating current with suitable instruments. Where necessary, take measurements under actual load conditions and compare the results with the motor nameplate and manufacturer's permitted operating limits.
Phase Loss in Three-Phase Motors
Phase loss is an important electrical fault to check in drum motors equipped with three-phase motors.
Common causes of phase loss
A blown fuse or faulty circuit breaker contact.
Burned or poorly connected contactor contacts.
Broken power cables or loose terminal connections.
An open circuit in the motor winding or internal wiring.
Effects of phase loss on the motor
If one phase is lost while the motor is running, the three-phase currents become severely unbalanced. The remaining windings may carry excessive current and overheat. If the protection devices do not disconnect the power supply in time, the winding insulation may deteriorate rapidly. In severe cases, the windings can burn out.
The risk is even greater when the motor is already operating under a heavy load.
The time it takes for damage to occur after phase loss depends on the load, motor construction, and protection settings. It is not correct to assume that every motor will burn out within a few minutes.
Deterioration of Motor Insulation
Motor windings rely on insulation materials to separate conductors and prevent short circuits between coil turns or between the windings and the motor core. When insulation deteriorates, electrical leakage, interturn short circuits, or ground faults may occur.
Moisture and contamination
If the drum motor's sealing structure is damaged, moisture, dust, or other contaminants may enter the housing and affect the insulation of the windings and associated electrical components. Prolonged exposure to humid or corrosive environments can also accelerate the deterioration of insulation materials and electrical connections.
Prolonged operation at high temperatures
Long-term overloading or poor heat dissipation can keep the motor windings at elevated temperatures. Continuous exposure to heat may cause insulation materials to age, become brittle, and lose their dielectric strength.
Mechanical vibration and wear
Persistent vibration, loose internal components, or improperly secured cables can cause friction and mechanical damage to winding insulation or lead insulation. If the insulation between conductors is damaged, interturn short circuits or ground faults may develop.
In addition, voltage pulses and high rates of voltage change produced by a variable frequency drive (VFD) can place extra electrical stress on motor insulation systems that are not designed for such operation. For motors powered by VFDs, confirm that the motor and drive are compatible.
Frequent Starts and Stops or Extended Starting Time
During startup, a drum motor typically draws more current than it does during normal operation. Frequent starts, repeated startup attempts within a short period, or an excessively long starting time can increase the motor's thermal load.
Frequent starting
Each startup subjects the motor windings to a period of elevated current. If the equipment starts and stops frequently, the winding temperature may rise again before it has had enough time to cool. Repeated thermal loading can accelerate insulation aging.
Difficulty starting under load
If a large amount of material has accumulated on the conveyor belt, or if the mechanical drive components have excessive resistance, the motor may take longer to start. Prolonged operation at high starting current generates additional heat and increases the risk of winding overheating.
Unsuitable starting method
Different motors and drive systems have different requirements for starting frequency, starting time, and starting method. Direct-on-line starting, soft starting, and variable frequency starting also have different current and thermal characteristics. The starting method should be selected according to the motor's rated parameters and actual operating conditions.
Starting current should not be assigned a fixed multiple of rated current for all drum motors. The permitted number of starts per hour must also be confirmed from the motor nameplate, product manual, and manufacturer's specifications.
How to Prevent Drum Motor Burnout
Preventing motor burnout requires attention to equipment selection, operating conditions, electrical protection, and routine maintenance.
Select the correct motor and control the load
Choose a drum motor according to the conveyed material weight, conveying speed, belt tension, and duty requirements. Avoid prolonged operation under excessive load. Also check whether idlers, bearings, the drum, and transmission components are binding or creating abnormal resistance.
Check the power supply and electrical connections
Regularly inspect the supply voltage, three-phase voltage balance, cable connections, and contactor contacts. Repair loose connections, burned contacts, and poor electrical connections promptly.
Install appropriate motor protection devices
Configure overload, short-circuit, phase-loss, and temperature protection according to the motor type and control system. For VFD-driven systems, set the motor rated current, overload protection, and other operating parameters correctly.
Maintain proper heat dissipation
Remove accumulated dust and debris from the drum surface and keep the surrounding area clear of obstructions that may restrict heat dissipation. For models equipped with dedicated cooling systems, inspect the fans and cooling passages regularly.
Control the starting frequency
Arrange equipment operation according to the motor's permitted duty rating and starting frequency. Avoid repeated starts within short intervals. For conveyor systems that require frequent starting, stopping, or speed adjustment, confirm that the motor and control equipment are suitable for the actual operating requirements.
Monitor abnormal operating conditions
During normal operation, pay attention to motor temperature, noise, vibration, and current changes. If excessive temperature rise, frequent tripping, unusual odors, or abnormal noise occurs, stop the equipment and inspect it. Do not repeatedly reset protection devices and continue operating without identifying the cause.
Custom Precision Machining for Drum Motors and Related Components
The operating reliability of a drum motor depends not only on the motor and electrical system but also on the machining quality of components such as the drum shaft, end covers, bearing mounting positions, and internal mechanical parts. For non-standard conveying equipment, these components often need to be manufactured according to specific structural requirements and assembly drawings.
Hansheng Automation provides drawing-based custom CNC precision machining for shafts, end covers, support blocks, and other equipment components. We support both single-piece prototyping and small-batch production for conveyor systems, packaging machinery, and other industrial equipment.
