Setting the parameters of a frequency converter is crucial during commissioning. Many first-time users of frequency converters are often overwhelmed by the sheer number and complexity of these parameters, which they may not fully understand. To address this, it's essential to grasp the fundamentals of frequency converter parameter setting: which parameters need to be set before trial operation; which parameters need adjustment during operation and their appropriate ranges; and how to prevent damage to the frequency converter due to improper parameter settings during commissioning.
Luosheng Company has been providing technical services for frequency converters for over a decade and has extensive experience in setting frequency converter parameters. The author interviewed Mr. Zhou, who has worked in the frequency converter product department for five years. He provided a detailed introduction to the parameters and definitions of several Luosheng frequency converter models and also demonstrated the debugging methods for the frequency converter parameters. According to Mr. Zhou, the parameters set for frequency converters may differ depending on the brand and series, but some parameter settings are the same regardless of the brand or series.
The author asked: Looking at the inverter sample, such as LENZE's SMD series, there are more than 30 parameters. Do users need to reset all of these parameters?
Mr. Zhou explained: Not all inverter parameters need to be reset. Generally, we divide inverter parameters into three types: first, parameters that do not need to be adjusted and can be kept at the factory settings; second, parameters that need to be preset before trial operation; and third, parameters that need to be adjusted during trial operation.
After installing the frequency converter, disconnect the output of the frequency converter and then connect the power supply of the frequency converter. (Note whether the rated power supply voltage of the frequency converter matches the external input voltage.) According to the parameter definition, confirm which parameters are consistent with the factory settings and operating conditions, such as the rated frequency of the motor, the input voltage, and the analog input/output signal type. If these signals are consistent with the operating conditions, these parameters do not need to be set and can be kept at the factory settings.
Some parameters need to be preset before trial operation, such as: external terminal operation, analog quantity operation, base frequency, maximum frequency, upper limit frequency, lower limit frequency, start-up time, braking time (and method), thermal electronic protection, overcurrent protection, carrier frequency, stall protection, and overvoltage protection.
There are also some parameters that are adjusted during the debugging process based on the operating conditions, such as operating frequency, acceleration time, deceleration time, speed range 1, speed range 2, speed range 3, and analog output ratio adjustment.
In addition to the three parameters mentioned above, there are some other parameters that are display settings for the frequency converter, which cannot be set but can be viewed.
Using the LENZE SMD series frequency converter as an example, Engineer Zhou explained to me one by one the parameters in the parameter table, which parameters do not need to be set, which need to be set before the output devices such as drive motors, and which need to be adjusted according to the operating conditions during the trial run. He also introduced some tips for adjusting parameters during the trial run.
For example: the principle for setting the starting time is that it should be short rather than long, and it can be set to 1.5~2s/kW. The overcurrent setting value can be appropriately increased, up to a maximum of 150%. If the motor stalls when the start button *RUN is pressed, it indicates that the load torque is too large and the starting torque is too small. In this case, the STOP button should be pressed immediately to stop the motor. The principle for setting the deceleration braking time is that it should be long rather than short. The starting frequency for light loads can be set to greater than 0, while the starting frequency for heavy loads generally starts from 0. The starting torque setting is the same as the starting frequency setting, which is beneficial for accelerating the start, especially under light loads. For heavy loads, the starting torque value is large, resulting in a large starting current, which is more likely to cause overcurrent (OC) in the low frequency range. Generally, it is appropriate to start the starting torque from 0. The standard base frequency setting is 380V at 50Hz, that is, V/F=380/50=7.6. Sometimes, when heavy loads start poorly and adjusting other parameters cannot improve the situation, the base frequency can be adjusted. The 50Hz setpoint is lowered to 30Hz or below. At this point, V/F > 7.6, meaning the output voltage increases, especially at lower frequencies (i.e., torque ∝ U²). There are generally three braking methods: regenerative braking is suitable for operating frequencies > 20Hz; DC braking is suitable for precise stopping or positioning and can be used in conjunction with regenerative braking, generally chosen for frequencies ≤ 20Hz; regenerative braking is suitable for ≥ 100kW motors with a speed ratio D ≥ 10, alternating high and low speeds or forward and reverse rotation, and short cycle times. In this case, regenerative braking is suitable, and the regenerative energy can reach 20% of the motor power. For loads such as water pumps and fans, free braking is preferable. Rapid, forceful braking (such as DC braking) can easily produce a severe "water hammer" effect.
During load commissioning, to protect the inverter and load equipment, the operating frequency setting should be gradually increased, and attention should be paid to the operation of the load. If any of the following situations occur, the inverter must be stopped immediately: the motor does not move, the motor overheats, or the inverter displays abnormal faults multiple times. The load should be disconnected and the following should be checked: ① whether the input voltage is normal; ② reconfirm the setting value (especially for parts related to starting); ③ the output equipment and the wiring connection to the inverter output side.
