英语翻译

英语翻译
V.SOLID STATE BREAKER HARDWARE
An example of a solid state circuit breaker for a DC application is shown in Figures 13 and 14.This device is rated for 2000Vdc and 800Amps,and was designed to protect
a propulsion drive inverter connected to a DC supply.Many of these breakers and inverter loads were connected to a common DC feed bus.
The primary series switches Q1 and Q2 are based on two parallel pairs of 900A,4500V IGBT modules,one in each DC bus line.If a short circuit occurs the current will rise rapidly through these switches and when it reaches a predetermined trip level,both devices turn off simultaneously.The IGBT pairs and protection devices are selected such that either pair alone can interrupt the current safely.The input bus is clamped with overvoltage protection circuitry based on an RCD snubber (R1-R3,D1,D2 and C1) and MOV protection devices RV1and RV2.
Additional auxiliary function also provided include switches S1,S2 and resistors R5,R6 used for a pre-charge of the output load,optional diodes D3 and D4 for isolation of the input,and dynamic brake switches Q3,Q4,and diodes D5,D6 for use with external DB resistors.Control and sensing circuitry provide current and voltage measurement,control signals,software and hardware overvoltage/overcurrent protection and isolated communication interface.The drawer like unit is water cooled,having dimensions of 42 x 16.5 x 7.5 inches,and a weight of 250lbs.
Due to the low inductance of the load (an inverter) and circuit delays,each breaker requires 30H of source side inductance to limit fault current di/dt such that peak IGBT current and voltage is within the SOA of the device.This added inductance results in the need for a two stage input clamp – an RCD for initial peak voltage limiting,and an MOV for bulk clamping.The IGBT turn off times are also reduced to approximately 2s to limit voltage overshoots.