The acceleration time is the time required for the frequency converter to rise from 0Hz to the base frequency (50Hz).This provision also applies to situations where the frequency of termination is arbitrary.In multistage speed operation, for example, a class of frequency set to 30 Hertz running speed, accelerating time setting for 30 s, is the speed class's actual acceleration time (up to 30 hz) is (30 hz / 50 hz) * = 18 s, 30 s and cannot understand for up to 30 hz need 30 s.

Set acceleration time should consider the following question: to accelerate the process takes time, speeding up too long time will reduce work efficiency, especially frequent start-stop devices, but accelerating time is too short to make the starting current is big, therefore, should be in the starting current and seek a balance between the production efficiency, on the premise of starting current allowed, try to shorten the acceleration time.In addition, the acceleration time should be appropriately extended when the inertia of the load equipment is larger, and the inertia of the load equipment can be shortened appropriately.

Starting power frequency, motor power frequency power supply is connected, a rotating magnetic field that is rated rotate synchronous speed, and motor rotor is in static state, the rotor winding and the relative speed of a rotating magnetic field is very high, so the induction electromotive force and induced current is large, the stator current can be up to 5 to 7 times the rated current.Variable frequency starting, starting instantaneous frequency inverter output frequency is very low, after starting with low frequency, acceleration time according to the preset gradually increases, so the speed and rotor winding of a rotating magnetic field and rotating magnetic field of relative velocity are also very exactly, so the starting current is small, generally can be controlled in rated current fluctuation.

Because the inverter output voltage of PWM waveform, high frequency pulse sequence standard sine wave, the spectrum envelope containing harmonic component, its transient voltage amplitude and the frequency is very high, so that the motor winding capacitance in high voltage field between shell and effect, induced a higher voltage (there was a certain amplitude of converter shell static voltage).Therefore, there is a warning in the use of the frequency converter to ensure a reliable grounding, which is the reason.In addition, in the industrial field, usually without a separate grounding line, and zero line in alternative, a lot of ground equipment shell share the same system with frequency converter, this will make the whole system to produce high voltage static electricity, the high pressure will produce strong electric fields, interfere with the normal work of the frequency converter.If such a situation occurs, the fault can be excluded as long as a single frequency converter control system is embedded in the system.

TT system (three phase four wire system) of the zero line access circuit, contains more harmonic and various clutter, sometimes there will be a few volts or even hundreds of volts, once the "to" connected to the zero line of frequency converter, could the harmonic and various clutter is introduced into the converter internal interference formation, affect the normal work frequency converter.Therefore, the general frequency converter should be independently grounded.

In the inverter control system, there are many occasions or extended before installing frequency converter using three phase four wire system leakage circuit breaker, the frequency converter operation, a frequency converter in the case of frequent tripping during normal use.Reason is because of the general inverter runtime contained in the output voltage harmonic component, so that the motor winding and shell, and the wire to the ground between parasitic capacitance, the parasitic capacitance through wires and earth, the earth and chassis, constitute the leakage current, when the leakage current is greater than the current value of residual current circuit breaker, leakage circuit breaker will move in the trip.Therefore, in the control system of using frequency converter, in case the above situation, need to replace the original residual current circuit breaker or setting up the current value of the residual