The issue of the operating frequency of variable-frequency motors

The rated frequency designed for domestic motor manufacturing is 50Hz； The rated frequency for motor designs manufactured abroad is 60 Hz. However, in normal practical use, the operating frequency of the motor should not exceed its rated value by much. If the operating frequency of domestic motors cannot exceed 50 Hz ； Some imported motors cannot operate at a frequency higher than 60 Hz. If the operating frequency exceeds the rated value, the motor’s performance will deteriorate. It’s not 3 Hz at low frequencies either; it’s usually around 10-15 Hz. This is merely a range of output frequencies for the design and manufacture of frequency converters.

Can an inverter-driven motor operate at a speed higher than the rated speed specified on its nameplate?

It is best for variable-frequency motors to operate at the frequency indicated on their nameplate as well. If the value exceeds the rated level, since the internal resistance of the motor remains unchanged, the voltage rises and the current increases; as a result, the motor overheats over time, reducing its lifespan.

The nameplate indicates a rated speed of 1470; no specification for the rated frequency is given. Is it possible to operate above the rated speed?

Don’t speed, or it will fall apart. Heat dissipation is also poor, which poses a serious risk to the motor.

This is the response from the manufacturer’s electrical engineering team: The motor used is a frequency conversion-specific motor, of the model YPT200L-4. It is a 4-pole motor, so at the standard power frequency of 50 Hz, its speed is 1470 revolutions per minute. Since it is a frequency conversion-specific motor, its maximum operating frequency range is 3–100 Hz. However, for the slurry pump, the required frequency range for this motor is 5–80 Hz; accordingly, the motor’s operating speed range is 147–2352 revolutions per minute. This is the reply from the electrical engineering team. Does this make sense? Please help analyze it.

If it has a rated speed, it shouldn’t be an inverter-driven motor; inverter-driven motors are specified by their operating frequency range. Please make sure.

The operating frequency of the motors in our company is generally between 20 and 55 Hz. If the frequency is too high or too low, noise levels increase, and the lifespan of the motors decreases

It also says 3-100 on our variable-frequency motors, which is exaggerated

Once the variable-frequency motor you purchase is manufactured, its operating frequency range is determined. You can check the frequency range parameters specified on the motor’s nameplate. The rotational speed increases by 20%, while the torque decreases by 20%. At higher frequencies, the rotational speed is likely to be too high, resulting in insufficient mechanical strength of the motor. Increasing the speed by 20% reduces the load capacity, increases heat generation and vibration; it is best not to use it, especially under heavy loads. Using a 50Hz motor at 60Hz accelerates its aging, as the materials and design parameters of 60Hz motors are superior to those of 50Hz motors. A decrease in air-gap flux leads to insufficient motor output. Since U ≈ 4.44fNΦ, it follows that U/f = 4.44NΦ; in other words, U/f ∝ Φ. Moreover, since 380 / 60 = 6.33 < 380 / 50 = 7.6, Φ will decrease, which results in insufficient output from the motor.