Lightning Damage

 Below are some pictures of parts of a Ziel Abegg lift motor drive (from a local hospital) that suddenly blew up.

This specific drive weighs in at 36.5Kgm (80pounds) and can drive a 37KW motor at 74A (or max 134A)
 

 Most of these drives follow a typical standard practice which is updated when new and hopefully better components are made available. In this drive, a pretty powerful example, individual motor power modules are used. Early models would have used large "discrete" SCRs, triacs, or more modern IGBTs with a rats nest of wiring, but integrated modules offer reduced manufacturing costs. In smaller drives U, V and W drive would be integrated into a single module.
 

 On the right are "snubbers" each using is a pair of resistors of 150 ohm, in parallel, with a series 0.15uF capacitor (in red) across the three mains phases. the resistors use 21SWG wire ends and each is fused open. The fusing current of this wire is 58A so some 116A must have flowed through the circuitry. Oddly each resistor still measures 150 ohms so the duration of the current must have been very short. This is also the evidence from the red voltage surge protectors which haven't disintegrated.
 

Below, a close up of the 3-phase mains input tracking under the circuit protectors. What was the purpose of the circuit protectors you might ask? Well, these are in place to damp out only minor surges not a direct lightning strike.
 

 A few clues on the upper surface but more evidence of what happened on the underside of the second of the two pcbs which were mounted over the heatsink. 
 

 Below, the line-up of motor drive modules (U, V and W) with that for the brake on the right.
 

 The bridge rectifier is soldered in place unlike the plug-in motor modules. Picture taken after cleaning away most of the soot.
 

A view of the rectifier which might include a monitoring facility of the inputs. Unlike many failed rectifiers all the diodes in the bridge are open circuit and in fact these parts rarely fail.

I interpret this to have a rating of 180A and 1600V
 

 A view of one of three of the three motor power modules on the left, and on the right the brake module which is slightly different. Ratings appear to be 220A and 1200V for the motor with 200A and 1200V for the brake.
 

 It remains to be seen what damage there is to the other components (and of course track ie. where did all that soot come from!) on the various circuit boards....

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