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Three-phase diode bridge rectifiers with a low source reactance cause considerable current harmonics in the AC supply, which may not meet the latest EMI regulations. At higher source reactance the bridge is more likely to operate in continuous conduction mode (CCM), leading to a reduction in harmonic current level. In the paper accurate analytical expressions are derived for the AC current harmonics, the input power and the power factor in CCM, which have been validated through numerical simulations and practical experiments. They can therefore be used with confidence for the design of power supplies with lower harmonic levels. Remedies are proposed to compensate for the drawbacks of CCM operation, using power factor correction capacitors and a single-switch inductor-less boost rectifier.
Date of Publication: 4 March 2005