Technical Support System principle of variable frequency power supply

Power supply through AC → DC → AC conversion is called variable frequency power supply , which differs from variable velocity & frequency controller, also from ordinary AC line conditioner. Main function of variable frequency power supply is to change existing AC grid power supply into stable and pure sine wave power supply with the needed frequency. The characteristics of ideal AC power supply are frequency stabilization, voltage stabilization, zero resistance, and voltage waveform being pure sine wave (no distortion). Since variable frequency power supply is quite close to ideal AC power supply, advanced countries are now increasingly using it as standard power supply, so as to offer the best power supply for electric apparatus, and check objectively the technical performance of electric apparatus in use. V ariable frequency power supply has two main categories: linear amplifier type and PWM chopper type.

Program-control variable frequency power supply of HY series, centered on microprocessor, made in the manner of MPWM, designed with active component IGBT module, and adopting digital frequency division, D/A conversion, instantaneous value feedback, SPWM and other technologies, making the capacity of individual machine reach 100 KVA, and output through isolation transformer to increase the whole machine's stability, owns such characteristics as being load adaptable, output waveform with good quality, easy operation, compactness and lightweight, and protective functions against short circuit, over current, over load, over heat, etc to ensure the reliable operation of power supply.

Function module of variable frequency power supply

The category of variable frequency power supply 's permissible load and the method of selecting capacity

Variable frequency power supply can bear all kinds of load with impedance characteristic, including the common load of inductance, of resistance and of commutation. If the load is different, the power capacity of variable frequency power supply needed is quite different, which great importance shall be attached to.

① .The category of load:

② .The primary characteristics of different loads:
·Resistance: power capacity = 1.1 × load power
·Inductive: power capacity = load start-up current/ load rated current × load power
·Commutation: power capacity = load current wave crest factor/ 1.5 × load power
·Mixed type: please properly select in accordance with the proportion of different loads.
Note ： For inductive load like refrigerator or air conditioner, please select power capacity in accordance with initial power.
(Usually initial power is 5-7 times of rated power)

Tri-phase alternating current supply IGBT PWN system structure, common structures

① .Separate type (Independent type) tri-phase alternating current supply, transformer structure without power supply, input non-isolation, output isolation.
Structure diagram:

·Three independent output transformer, three sets of converters, as many as 12 IGBT are used
·Three sets of converters can also share one set of rectifier.
·Tri-phase is formed by the integration of three complete single-phase. You can use either single-phase (any single phase therein) or tri-phase.
Applied to tri-phase equilibrium and disequilibrium (100% disequilibrium) load, it can be made into a single machine case or three machine cases according to demand. Different structure, different cost, and, of course, different performance!!

② .Low cost tri-phase alternating current supply, transformer structure without power supply, input non-isolation, output isolation.
Structure diagram ：

③ .Independent tri-phase alternating current supply, transformer structure without output, input isolation, output non-isolation
Structure diagram ：