Since it is precharging not completed, let's follow the route where the current comes in, checking from outside to inside.
1. Incoming Line Power Supply Has Problems
Many repair workers, upon seeing the drive error, hurry to tear down the inverter, actually the first step should be taking a multimeter to measure the cabinet's three-phase incoming line voltage.
Think about it, if the factory's voltage today is on the low side (for example originally 380V dropped to 320V), or the front-stage fuse broke one phase (missing phase), the incoming water pressure was originally not enough, how could the DC link capacitors charge to the preset voltage within the specified time?
On-site details: especially in old workshops, or when high-power equipment next door (such as electric arc furnaces, big punch presses) suddenly starts up, the power grid voltage will be pulled low in an instant. Running into F30027, first measure if L1, L2, L3 are stable.
2. Main Contactor (Main Contactor) "Strikes" or Sticks
When precharging is near ending, the main contactor must pull in in time. If the main contactor is broken, for example:
* The coil is burned or the control circuit didn't send power over;
* Contacts are oxidized, eroded, with bad contact;
* Auxiliary contacts fault, the motherboard cannot receive the feedback signal of "I have pulled in";
Then the system will feel "why are the precharging resistors still strung in series? Is precharging timed out?" and directly throw you an F30027. On site if you can hear the contactor "click" make a sound and then immediately bounce open, focus on checking this guy.
3. Parameters Cannot Match the On-Site Voltage
This is particularly common when replacing spare parts or reinstalling systems.
For example, originally the on-site three-phase power was 380V, but the newly replaced drive's internal parameters were set to a 480V system. The drive will silly-mindedly measure the precharging voltage according to 480V standards, when charged to 380V it feels it only charged half, waiting a long time and not getting the target voltage, naturally it reports timeout.
Suggest going to check the drive's incoming line rated voltage parameter (such as P0210 etc.), to see if it can match the actual on-site voltage.
4. DC Link (DC Link) Internal Leakage or Short Circuit
If the power supply and contactor are both good, but the capacitors cannot charge up no matter what, then you have to suspect whether the DC link is leaking electricity.
For example:
* DC link capacitors aging, bulging, leaking liquid and short-circuiting;
* IGBT module internal input end broken through;
* There are metal scraps or oil dirt on the board causing short circuit to ground.
This is just like while the reservoir is pouring water, the bottom has a big hole desperately leaking water, the water level no matter what cannot rise up. Note: before checking the DC link, must thoroughly cut off power, and use a multimeter to confirm the DC link voltage dropped to the safe range (below 36V) before starting measurements!
5. Precharging Resistor Burned Open, or Precharging Relay Broken
Those few precharging resistors of several ohms to several tens of ohms in the precharging circuit are among the components with the worst working environment. Every power-on they have to bear huge current impact.
If the precharging resistor simply burned open (open circuit), then the capacitor cannot even charge one volt of power; if it is the relay contact controlling the precharging that is broken, the circuit is not connected, and likewise cannot charge power. In this situation, disassembling the drive and taking a multimeter to measure the precharging resistor's resistance value will immediately yield results.
6. "Thermal Protection" Caused by Frequent Power Toggling
Some operators, upon encountering an error, like to play the "great restart trick": cut power—send power—cut power—send power, switching back and forth several times within one minute, trying to "touch luck". This is way too life-taking! The precharging resistor will violently generate heat every time power is sent, frequent power-on will make the resistor temperature soar. Certain
Siemens drives carry a precharging resistor thermal protection mechanism, once detecting the resistor is too hot, it will forcibly pause precharging, and will also pop out F30027.
Solution: hurry up and stop your hands! Turn off the equipment, quietly leave it for 10 to 15 minutes, let the precharging resistor thoroughly cool down, and then try sending power again.
7. Big Common DC Bus System, Total Capacitor Amount Exceeded Standard
This belongs to special working conditions. For example, in large automation production lines or multi-axis systems, several drives are hung on the same shared DC bus, or externally hung with a very giant capacitor array. The total capacitor amount is too big, the originally preset 2-second precharging time is simply not enough to use, before the capacitors are poured full, the system stopwatch reached the end. At this time you need to appropriately relax the precharging monitoring time in the parameters.
