VFD maintenance
Home » Blog » VFD maintenance » Variable frequency drive power anomalies

Variable frequency drive power anomalies

Variable frequency drive power anomalies can be divided into following three types: phase loss, low voltage and power off, sometimes they maybe appear mixed. The main reasons for these anomalies are transmission line impact by wind, snow and lightning, sometimes it's the power supply system appear ground wire and phase short circuit. The lightning is very different due to geographical and seasonal factors. In addition to voltage fluctuations, some power grid or self-generation units will have frequency fluctuations, and these phenomena maybe appear repeated in short times, in order to ensure normal operation, the variable frequency drive power supply also need to make corresponding requirements.

If there is a direct-start motor or cooker or other equipment near the variable frequency drive, to avoid voltage decrease when these devices power on, those devices power supply should be separated with the VFD power supply to reduce influence each other.

For the applications require continues operation in instantaneous power off, in addition to select appropriate VFD drives, we also need to consider the motor load deceleration ratio. When the variable frequency drive and external control loop are adopted instantaneous power off compensation, we need to prevent over current during acceleration by detect motor speed when power on.

For the application requires continuous operation, it's better to install additional automatic switching uninterrupted power supply devices. Like adopt diode input and single-phase control power variable frequency drives, it can continue work even if in phase loss status, but individual rectifier device current is too high, and the capacitor pulse current also high, it's not good for the variable frequency drives reliability and service life in long time running, so we should handle it the early the better.

Post a Comment:

Calculate (1 - 7) =

You may also like:

I hate to call them harmonic currents. The do submit to Fourier analysis, but you are probably dealing with AC to DC power supplies. If you look at the current pulses, you will see that each pulse is about 1-2 ...
For a "physical" interpretation, reactive current (power/KVA flow), in my opinion is best looked at from the perspective of a generator connected directly to an infinite bus (in LV generators this is the norm).
Coming from a signal processing and communications theory background, but with some experience in power design, I can't resist the urge to chime in with a few remarks. There are many engineering methods to ...
The high frequency edges of switched waveforms can cause capacitively coupled currents to flow from windings to frame, returning through the bearings, and these can accelerate corrosion in the bearings, ...
Can an AC drive to replace the mechanical gearbox that used to decrease motor speed in conveyor application i.e to use a motor that will drive the load directly throw a coupling, belt or chain, without ...
Gozuk Service Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.


Like pumps, fans consume significant electrical energy while serving several applications. In many plants, the VFDs (variable ... energy consumedA frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ... Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ... Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ... Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...

In Discussion