DC power supply circuit

A dc power supply circuit for rectifying ac power to be dc power and for supplying the dc power to a dc drive unit, comprising:

• a rectifier for rectifying ac power to be dc power;
• at least one first dc circuit breaker connected between said rectifier and said dc drive unit;
• a return circuit returning dc power from said dc drive unit to said rectifier;
• a second dc circuit breaker connected to said return circuit to interrupt power transmission therethrough;
• and
• current decreasing means connected to said return circuit in parallel with said second dc circuit breaker for decreasing current flowing in said return circuit when said second dc circuit breaker is operated to interrupt power supply therethrough;
• wherein said second dc circuit breaker has a larger interruption capacity than that of said at least one first dc circuit breaker.

A dc power supply circuit for converting ac power into dc power and for supplying the dc power to a dc drive unit, comprising:

• a semi-conductor converter for converting ac power to dc power;
• a plurality of first dc circuit breakers connected to said power supply circuit between said semi-conductor converter and said dc drive unit;
• a return circuit returning power from said dc drive unit to said semi-conductor converter;
• a second dc circuit breaker connected to said return circuit to interrupt power transmission therethrough;
• and
• a current decreasing means connected to said return circuit in parallel with said second dc circuit breaker for decreasing current flowing in said return circuit when said second dc circuit breaker is operated to interrupt power return therethrough;
• wherein said second dc circuit breaker has a larger interruption capacity than that of each of said first dc circuit breakers.