Patent ID: 9673695
Date: 2017-06-06
CPC Classifications: H02H,H02M

Claim:
1. An adjustable speed drive (ASD) circuit comprising: an input connectable to an AC source; a solid-state switch rectifier bridge connected to the input to convert an AC power input to a DC power; a DC link coupled to the solid-state rectifier bridge to receive the DC power therefrom; a DC link capacitor bank comprising at least first and second capacitors connected to the DC link to smooth the DC link voltage, each capacitor of the DC link capacitor bank having a capacitor voltage thereacross; a pre-charge circuit coupled between the input and the DC link capacitor bank, the pre-charge circuit comprising a plurality of pre-charge relays each operable in an on state that allows the AC power input to power the solid-state switch rectifier bridge during a normal operating state and an off state that allows the AC power input to pre-charge the DC link capacitor bank through a pre-charge resistor of the pre-charge circuit during a pre-charge operating state; and a protection circuit comprising a protection relay coupled between the plurality of pre-charge relays and the DC link capacitor bank, the protection relay operable in an on state that prevents the pre-charge circuit from connecting to the DC link capacitor bank when a capacitor short circuit occurs and an off state that allows the pre-charge circuit to electrically connect to the DC link capacitor bank.