Siemens inverter selection considerations - Solutions - Huaqiang Electronic Network

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1) When choosing an inverter, it's essential to consider the load type. For constant torque loads, the Siemens MM420/MM440 is a suitable choice. If the load involves fans or pumps, the MM430 model would be more appropriate. 2) Always base your inverter selection on the actual current rather than the motor’s rated power. Keep in mind that inverters introduce harmonic distortions, which can lower the motor's efficiency and power factor. This might cause the motor current to rise by about 10% and temperature to increase by approximately 20%. Ensure you account for this when selecting both the motor and inverter, leaving enough margin to avoid overheating and extend the motor's lifespan. 3) If using long cables with the inverter, take steps to reduce the impact of ground coupling capacitance. It's recommended to either step up the inverter by one or two levels or install an output reactor at the inverter’s output to prevent performance issues. 4) In special environments such as high ambient temperatures, high switching frequencies, or high altitudes, the inverter may need to be oversized due to derating effects caused by these conditions. 5) When controlling multiple motors in parallel, ensure the total cable length from the inverter to the motors stays within the inverter’s limits. If not, choose a larger inverter. Also, note that only V/F control mode is available, and overcurrent protection won’t be effective. Fuses should be added on each motor side for safety. 6) High-speed motors produce more harmonics, increasing inverter output current. Therefore, select an inverter slightly larger than what’s needed for a standard motor. 7) When driving pole-changing motors, pay attention to the inverter’s capacity to ensure its maximum current rating is below the inverter’s output limit. Always stop the motor before changing the pole number to avoid damage. 8) For explosion-proof motors, the inverter must be placed outside the hazardous area since it doesn't have an explosion-proof design. 9) When using an inverter with a geared motor, consider the lubrication method. At low speeds, there are no restrictions, but at high speeds, oil may be thrown out, so always respect the maximum speed limit. 10) With wound rotor motors, the winding impedance is lower than in squirrel cage motors, making them prone to overcurrent trips. Choose an inverter with a slightly higher capacity. These motors often have high flywheel torque, so careful setting of acceleration/deceleration times is crucial. 11) Synchronous motors reduce inverter output by 10–20% compared to commercial frequency power. The inverter’s continuous output current should exceed the product of the motor’s rated current and the synchronous pull-in current. 12) For compressors or vibrating machines with large torque ripple, or hydraulic pumps with peak loads, selecting based on motor rated current or power may trigger overcurrent trips. Choose an inverter with a higher rated output current than the motor’s peak current. 13) Submersible pump motors typically have higher rated currents, so the inverter must have a higher current rating than the motor’s rated value. 14) Roots blowers require careful inverter selection due to their high torque and starting current. Ensure the inverter has sufficient capacity to handle the load. 15) Check the inverter’s protection level to match the site conditions. Dust and moisture can affect long-term operation if not properly addressed. 16) Single-phase motors are not suitable for inverter drive. 17) Even if the motor load is light, avoid using an inverter much smaller than the motor’s capacity. Larger motors may generate more ripple current, potentially exceeding the inverter’s current tolerance. 18) If the inverter has a self-contained power supply, adding a line reactor is highly recommended for better stability.