The power supply should be sufficient and stable
First of all, to ensure sufficient and stable power for a three-phase motor, check whether the supply voltage and current meet the motor’s requirements. Normally, a voltage of 380V or higher is needed for three-phase motors. If the voltage is too low, this would lead to insufficient motor power and lower production efficiency. Even if a 15kW-rated motor is used, if the supply voltage remains under 350V for an extended period, the motor’s actual output power can decrease by up to 10% to 20%, resulting in reduced production efficiency and a shortened motor lifespan.
Stability in the power supply system is required. Operating the motor under unstable power conditions may lead to overheating or burnout of the motor windings. The unstable nature of power supplies leads to almost 30% of failures in motors. Companies should first install a stabilizer or UPS power system to ensure power stability before installing any motor. Additionally, one must see if the available power capacity is sufficient for multiple motors running simultaneously. For example, if the workshop uses 10 motors of 7.5kW capacity at the same time, the total power requirement would be 75kW. If the installed total power supply capacity is less than 100kW, voltage drops could happen, directly impacting the normal operation of the production equipment. In industries that require high power quality, such as precision machinery or the pharmaceutical industry, the quality of power has a direct relationship to product quality and output.
Proper wiring ensures safety
Safe operation of the three-phase motor mainly depends on proper wiring. Improper wiring can cause the motor not to start or even burn out the coils. For example, a three-phase motor with a rated power of 30kW has a starting current that can be five to seven times the rated current, roughly 200 to 300 amps. Incorrect wiring, such as connecting in delta (∆) when a star (Y) connection is needed, can result in excessive starting current, possibly causing a short circuit or even a fire. There are mainly two wiring methods for three-phase motors: star connection and delta connection. The star connection is applicable to small motors and usually applied for light-load or no-load starts. Larger motors utilize delta connections and can start at rated voltage, providing more starting torque. If the wiring is wrong—for example, connecting in delta where a star connection is required—the motor’s starting current could be too high, perhaps burning the motor instantaneously when it starts.
In practice, many motor failures stem from incorrect wiring. Over 20% of motor failures are related to improper wiring. When installing a three-phase motor, one must diligently consult the wiring diagram to ensure each wire is connected to the correct terminal. For motors from brands like ABB and Siemens, manufacturers normally provide detailed wiring diagrams and manuals inside the junction box. Installers need to follow these wiring instructions very strictly. In everyday applications, businesses should regularly ensure that the motor connections are tight, especially in operations with significant vibration, like mining or steel mills. Over time, long-term vibration causes connections to loosen, leading to poor contact, overheating, or even burning out the motor. When installing, utilize standard wiring materials and tools. Using high-quality copper wires and connectors that match current specifications can reduce contact resistance and improve the reliability and safety of the connections. Wire terminals and connectors should be tightened using torque wrenches to ensure solid connections. These minor details directly affect the safety and life of three-phase motors.
Good ventilation and heat dissipation effect
During operation, a three-phase motor generates a lot of heat. Poor ventilation and cooling can result in the motor’s internal temperature rising very rapidly to dangerous levels. A 22kW-rated motor, for example, will generate upwards of 15,000 kcal of heat per hour when operating at its continuous full-load capacity—equivalent to a small electric heater. If the heat does not dissipate in time, it will accumulate inside the motor, increasing the coil temperature. This would accelerate insulation aging and shorten the motor’s lifespan. The cooling performance of a motor directly influences its service life and work efficiency. Every 10°C increase in the motor temperature halves the lifespan of its insulation materials. If a motor were to operate for a very long time at an ambient temperature of over 80°C, it would decrease the motor’s life from 20 years to 10 years or even less. Motors in high-temperature and dusty environments should be equipped with forced cooling units such as axial fans or a water-cooling system.
Poor cooling has been the source of quite a few serious accidents. Good ventilation and cooling must be guaranteed, and it is very important to choose the right place for installation. There should be sufficient space around the motor for heat dissipation, with at least 50 cm of clearance for ventilation. The heat would not easily dissipate into the air when installed in enclosed spaces, causing local overheating. Some factories install motors in narrow mechanical rooms, thereby saving space but resulting in poor ventilation. This can cause not only the overheating of the motor itself but also increase the temperature of the mechanical room, thus affecting the operation of equipment around it. The fan and cooling fins of the motor should be checked and cleaned regularly. In some production processes, the surrounding air contains much dust and oil that could stick to the motor’s cooling fins, reducing cooling efficiency.
