Variable Frequency Power Supply Types of Loads and Capacity Selection Methods
①. Types of load characteristics:
Resistive: Power supply capacity = 1.1×Load power
·Inductive: Power supply capacity = Load starting current / Load rated current × Load power
·Rectifier: Power supply capacity = Load current crest factor / 1.5 × Load power
·Mixed type: Please select appropriately according to the proportion of different loads
Note: For inductive loads such as refrigerators and air conditioners, the power supply capacity should be selected based on the starting power.
(Starting power is generally 5-7 times the rated power)
Three-phase AC power supply IGBT PWM system structure, common structures
①. Separate (independent) three-phase AC power supply, without power transformer structure, input not isolated, output isolated
Features: ·One output transformer with three sets of windings, one converter, only 6 IGBTs used
·Can only supply three-phase loads (cannot be used individually per phase), not suitable for unbalanced three-phase loads
·This structure can only be made in one chassis
③. Independent three-phase AC power supply, without output transformer structure, input isolated, output not isolated
·One power transformer, three inverters, 12 IGBTs used
·Three-phase is formed by complete single-phase integration, can be used as single-phase (using any one phase) or three-phase
Suitable for three-phase balanced and unbalanced (100% unbalanced) loads, can only be made in one chassis
Variable frequency power supplies can drive loads with various impedance characteristics, including common inductive, resistive, and rectifier loads. It is important to note that different load types require significantly different power capacities for the variable frequency power supply.
