What is the temperature rise of the motor? How much sho […]
What is the temperature rise of the motor? How much should the temperature rise range be controlled? Electric Motor Manufacturer answer
Motor temperature rise means that the temperature rise refers to the value of the stator winding temperature higher than the ambient temperature under the rated operating condition (the ambient temperature is specified to be 35 ° C or 40 ° C or less. If the specific value is not indicated on the nameplate, it is 40 °C). The current heat effect occurs after the conductor flows through, and the temperature of the conductor surface continuously rises until it is stable over time. The stable judgment condition is that the temperature difference between the temperature of any test point and the average value of the ambient temperature of the last quarter of the test is not more than 2K at all test points within one hour test interval. The unit is K.
The temperature rise of a certain part of the motor is the difference between the temperature of the temperature of the part of the cooling medium, and the unit is K. The temperature rise of the motor includes the temperature rise of the stator and rotor windings, the temperature rise of the stator and the rotor core, the temperature rise of the collector ring and the allowable temperature of the bearing (described above). The temperature rise of the B-class motor winding is limited to 80K; the F-class motor is also 80K according to the B-class evaluation; according to the F-class evaluation, it is 105K. According to the corresponding standard, the B-class insulation material can withstand the working temperature for 130°C for a long time. Long-term withstand 155 ° C, according to the actual maximum operating temperature of the motor 40 ° C calculation, the motor allows the working temperature is:
Class B ≤ 120 ° C (ring temperature 40 ° C + temperature rise 80) <130 ° C;
F grade ≤ 145 ° C (ring temperature 40 ° C + temperature rise 105) < 155 ° C;
It can be seen that there is a margin left. The F-level is more large according to the B-level assessment. In actual operation, it is necessary to judge whether the motor temperature is too high. Due to equipment limitations, the iron core temperature can be measured with a sufficient range of alcohol thermometer for rough judgment. Grade <120 ° C, F grade <145 ° C is qualified, can be used with confidence, close to the limit can contact the manufacturer.
Compared with the old series motors such as J5 and R, because the protection level of the old series motors is extremely low, most of them are not up to IP21, the insulation level is mostly B grade, or even lower, and the temperature rise limit is also low, so the new series The temperature rise of the F-class motor is higher than that of the old series, and the performance indicators of the old series of motor efficiency and power factor are much lower, and the quality cannot be compared with the new series.