Purpose of Motor Temperature Rise Test

All types of low-voltage switchgear equipment testing projects, with temperature rise testing being particularly special. In low-voltage switchgear equipment, especially drawer-type switch cabinets, there are more than twenty branch feeder circuits, in addition to the main incoming line circuit. According to the National Standard of...In compliance with the requirements of "GB 7251 Low-Voltage Switchgear and Control Gear" and "GB/T 10233 Basic Test Methods for Low-Voltage Switchgear and Control Gear," the main circuit and branch circuits of the complete switchgear must simultaneously pass the rated current for temperature rise tests. The temperature of each component of the low-voltage complete switchgear must be measured to verify if the tested item meets the standard requirements.

The characteristics of the temperature rise test for traditional low-voltage complete switchgear equipment are:

The test duration is relatively long, typically requiring 8 to 10 hours, or even longer, for the temperature rise test.

② High energy consumption in trialsThe tested samples must run at the rated current for an extended period, dissipating energy on the load, hence many manufacturers opt to conduct tests at night to avoid peak electricity usage.

③ The testing process is monotonous and tedious, requiring test personnel to frequently adjust loads and repeatedly measure temperature values for extended periods.

Traditional Testing Methods

Currently, the widely used method for temperature rise tests of domestic traditional low-voltage complete switchgear equipment involves connecting a large capacity multi-path transformer at the power input end of the item under test. The transformer directly applies an AC low voltage to the item under test through the transformation of current.A power supply of 8-12V and high current (4000-10000A) is used, and variable resistors or current regulators are connected to the feeding loops of the tested product as loads to obtain the test current. By adjusting the variable resistor or current regulator, the output current is adjusted to reach the set current value. Figure 1 is the principle block diagram of the temperature rise test for traditional low-voltage complete switchgear.

Due to the large size of the high-capacity multi-path transformer equipment itself, when equipped with variable resistors or current regulators, it occupies a significant amount of floor space, requiring ample laboratory space; additionally, the heavy and immobile nature of the equipment precludes its use for conducting experiments.Multiple devices conduct simultaneous inspections.

Additionally, due to fluctuations in grid voltage, changes in wire resistance within the current-carrying circuit, and variations in the resistive heating of the load itself, the test current varies accordingly. Operators must frequently adjust resistors or current transformers to maintain a constant current, which is time-consuming and labor-intensive, yet precision is still not guaranteed.Under low-voltage, high-current conditions, a significant amount of reactive non-active power loss is generated, with electrical energy directly consumed in copper busbars, resistors, or converters. This not only affects the quality of the power grid but also leads to considerable energy waste.

Additionally, the temperature testing instruments commonly used for temperature rise tests of low-voltage switchgear complete sets typically feature multi-channel capabilities.(like Multi-Point Temperature Scanner), the hot junction of the thermocouple is fixed to the measurement point of the test component using an adhesive bonding method or by drilling holes and embedding, requiring multiple thermocouples to collect data, and calibration is necessary before testing.Multiple thermocouples are prone to high failure rates. It is apparent that traditional equipment for temperature rise testing is characterized by its large size, lengthy testing time, high energy consumption, low efficiency, high failure rates, and poor operability.