[introduction]When using the applied program that does not need to move amain, frequency conversion driver can reduce cost of specific power consumption. The purpose of VFD is to make the speed of the equipment of electric machinery drive and the speed look that want load match. Driver of other alternating current cannot realize this.

Why should use electric power drive?

When using the applied program that does not need to move amain, frequency conversion driver can reduce cost of specific power consumption. The purpose of VFD is to make the speed of the equipment of electric machinery drive and the speed look that want load match. Driver of other alternating current cannot realize this.

In industrial domain, the electric power of 65% is used up come from electromotor. Optimize electromotor through using transducer, can reduce the electric power of 70% to use up.

To ensure electric machinery moves with effective rate and precision, in order to raise manufacturing level, the proposal uses frequency conversion driver.

Use transducer controls equipment to be able to prolong the service life of equipment, decrease uphold requirement, because they can achieve appropriate electric machinery rate. The overload that frequency of transducer control electric machinery and voltage can offer, owe press and press protection too.

The type of VFD

Put in the VFD of 3 kinds of types: Voltage source inverter (inverter of VSI) , current source (CSI) and inverter of pulse width modulation (PWM) .

VSI is common VFD type, use simple diode circuit to get dc signal from inside communicating signal among them, have the capacitor of energy of a memory. Next, inverter circuit uses the energy that capacitor stores to convey its to output.

What CSI relies on is electric current is not voltage, arise depend on the flowing output of alterable voltage limits. Use brilliant brake is in charge of bridge-type inverter to replace diode bridge-type commutator to generate voltaic square wave.

The working principle of VFD

Use VFD, the rotate speed of electric machinery is controlled through inputting the frequency of voltage, supply its electric machinery again next. Communicating a movement of driver is alternating current of 60 Hz, three-phase changeover is dc, it is dc inversion bogus three-phase frequency conversion next, enter connective electric machinery directly.

The frequency that enters electric power converter is 60 Hz, but the frequency that outputs electric machinery from converter has adjustable alterable frequency, in order to realize a needed electric machinery rotate speed.

Converter and inverter make two bodies of PWM communication gearing.

Graph 1. VFD job block diagram. The picture is offerred by Simon Mugo

Compose of line of alternating current source makes the three-phase power system of converter power supply. Line of alternating current source moves with 60 Hz frequency.

This converter uses rectifier to input 60 Hz communication changeover to output voltage for dc.

Graph 2. Converter part labour is constructive. The picture is offerred by Simon Mugo

The dc output that electric power converter offers is very crude; Accordingly, must use flowing method to ensure output volts d.c. is roughly constant. Action of wave of this kind of filter happens between changeover and inversion phase. Flowing hind, dc sends inversion level directly.

Graph 3. Principle of inverter part job pursues. The picture is offerred by Simon Mugo

The action of inverter part is generation communication output, use at drive electric machinery. Happen in inverter to and negative to switch, produce pulse rally thereby.

Frequency of PWM drive output is to pass amid infuse of a half-period the half-period infuse negative pulse after pulse is tightening therewith comes pilot.

Sine wave is outputted by narrow comprise with broad sine wave. Narrow state inferior output voltage is worth, and wide state taller voltage is worth. Different width formed pulse width modulation. This graph shows every half cycle has 6 pulse.

Flux – volt / hertz comparing

Bring to bear on to induction motor electric current can bring about electromotor rotating flux of the generation in magnetic field, produce torque thereby. Be fully loaded with torque for generation, flux must keep constant. Control electromotor keeps constant flux need calls volt one kind / the special method that hertz compares. This kind of method makes voltage and frequency raise identical cost in proportion, in order to produce good electromotor torque.

Graph 4. The voltage of every hertz is compared. The picture is offerred by Simon Mugo

For example, if voltage is 430 V and frequency is 60 Hz, criterion volt / hertz comparing is 430/60 or 7.2 V/Hz.

The action of VFD is to maintain voltage and frequency to compare constant. If cannot maintain this constant, electric machinery electric current can become not stable, can reduce torque thereby.

Electric machinery rotate speed

Electric machinery rotate speed can use formulary computation rate (RPM)= frequency (Hz) × 120n

Where beN= the utmost is counted

For example, be 60 Hz to frequency 2 extremely electric machinery, its speed can determine rate through the following formula (RPM) =60 × 1202=3600RPM

VFD advantage
Save the sources of energy
Use up extremely low electric machinery to start electric current
Installation is simple
Install to use up low kilovolt
Have relative to higher power factor
Reduce the mechanical stress of the leather belt in the process that start and electric machinery and thermal stress

VFD application

Stock is transmitted on conveyer belt, because it was offerred,start smoothly.

Because VFD operates noise minimum, because this uses automatic system to open and close an entrance door

Because reduced power comsumption, decreased to safeguard, prolonged equipment life, promote the promotion of engine control and stock.

The key of frequency conversion driver wants a place

Dynamoelectric communication driver is used at controlling the torque of mobile, speed and direction.

Dynamoelectric communication driver is divided be alterable driver or constant driver, alterable driver is used at the electromotor that moves with variable rate.

The account that uses dynamoelectric communication driver is to reduce the sources of energy cost and use up, through more rigorous course control raises yield, prolong equipment life and decrease safeguard.

VFD uses frequency to control the rate of electric machinery, the frequency that inputs signal among them is controlled before infuse electric machinery.

What VFD uses at conveyer belt is smooth start, control as the automatic system that open and closes an entrance door and the promotion machine that regard promotion as stock.

 

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