When a power-frequency motor is used with frequency conversion, what is the frequency conversion range?
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My company usually uses power frequency motors combined with inverters for variable-frequency operation; therefore, I would like to know what the frequency range of these inverters is Are there any relevant regulations?
This post was last edited by zhaohh3211 on 2010-7-13 at 13:12, using a power-frequency motor with an inverter whose frequency range is 0(5)–50 Hz.
Generally speaking, it is best to use variable-frequency motors whenever possible! If the requirements cannot be met, the frequency range for ordinary motors depends on the motor’s rated frequency. The theoretical value should be 0 to the motor’s rated speed. However, usually, both too low and too high motor speeds can affect the motor's lifespan. It’s too low; the motor runs slowly. Firstly, heat dissipation is poor, and secondly, bearing lubrication is also affected ； It’s too high; when the motor operates at high speeds for an extended period, the lifespan of its bearings is reduced, and the vibration level of the motor also increases. Based on experience, it is best for the speed to be no lower than 25% and no higher than 20% of the rated value.
Reply to 3# qhwangyz: Based on your experience, is the allowable frequency range for variable-frequency motors 37.5HZ to 60HZ? So it can still be used in 60HZ situations?
It is generally used at frequencies below 50HZ, as the power frequency of alternating current in our country is 50HZ. When operating at low speeds, the ambient temperature needs to be taken into account; when the temperature is low, the frequency can be reduced further.
Generally speaking, there should be no problem with a quadrupole motor operating at 60Hz (it has been in use for 15 years already). However, it should be noted that issues such as higher motor temperatures and a shorter replacement cycle for bearings may arise.
Of course, the motor’s speed can be reduced further, to around 20 Hz, but the problem is that this would require adding an additional cooling fan to help dissipate heat from the motor. Or specify during the design order that an independent fan be used for motor cooling!
Reply to 6# qhwangyz: If a 4-stage motor can be used at 60HZ, what about a 2-stage motor?
For a regular bipolar motor, it’s best not to exceed its rated speed! Of course, for dedicated variable-frequency motors, it is sufficient to use the frequency range provided by their manufacturing. For example, the special motors used in winding machines in the fiber industry can reach speeds of over 3000 revolutions per minute!
This post was last edited by zhaohh3211 on 2010-7-13 at 13:15. Theoretically, it should be between 0–60Hz, but due to the use of frequency converters with motors, it’s best to keep it within the range of 15–50Hz. If the frequency is too low, heat dissipation becomes problematic; if it’s too high, the motor’s lifespan will be reduced.