The core difference between motor overload and overcurrent lies in the cause-and-effect relationship: Overload is one of the common causes of overcurrent, but overcurrent is not entirely caused by overload. There are significant differences between the two in essence, scope, and manifestation.
In essence, they are in a “cause” and “effect” relationship. The essence of overload is that the motor is “overburdened”, referring to the actual load (such as mechanical resistance) that the motor bears exceeding its rated design capacity. It is a description of the load state and falls under the category of “cause”. On the other hand, the essence of overcurrent is that the motor’s “current exceeds the standard”, meaning the actual operating current exceeds the rated current value. It is an abnormal manifestation of electrical parameters and belongs to the category of “effect”. Overload forces the motor to increase current to maintain operation, which may lead to overcurrent. However, overcurrent can also be caused by other non-overload factors and does not necessarily rely on overload to exist.
In terms of the causes, the two have overlapping but not identical scopes. The causes of overload are all directly related to “load” and relatively simple, such as a sudden increase in the load of mechanical equipment driven by a motor, an inappropriate motor selection resulting in “a small horse pulling a big cart”, or a malfunction of mechanical transmission components causing a sharp increase in operating resistance. However, the causes of overcurrent are more extensive. Besides the above-mentioned overload scenarios, they also include faults in the motor or circuit themselves, which are unrelated to the load, such as short circuits in the stator winding, damage to interphase insulation, abnormal power supply voltage, and motor phase loss. These non-overload factors can also lead to excessive current.
In terms of manifestation and consequences, there are also differences in the emphasis of the two. The manifestation of overload is more inclined towards the “mechanical aspect”, with the motor speed significantly dropping during operation, the body becoming “weak”, difficulty in driving the load, increased mechanical noise, intensified vibration, easy wear and tear of transmission components such as bearings, and bending or fracture of the shaft. Long-term overload first causes damage to mechanical components, and then leads to electrical faults (such as overheating and burning of the winding). The manifestation of overcurrent is more inclined towards the “electrical aspect”, with the core being an excessive current value. In some cases, there may be no obvious mechanical abnormalities; if caused by non-overload factors (such as short circuit), the current will suddenly increase sharply, possibly burning the winding within a short period of time, and even triggering the trip of the leakage protection device. The consequences mainly focus on electrical component damage, while mechanical components may not be directly affected. In simple terms, overload is always accompanied by overcurrent, but overcurrent does not necessarily result from overload.
Post time: Dec-02-2025