Overload of 3 phase rectifier 1

[govender1]

I would like to know from someone if an incoming phase is burnt off will a three phase rectifier continue to operate and will this cause the rectifier to go into over load. Recently we had a phase failure and the rectifier diodes popped.

I know in a three phase induction motor, if the motor looses a phase, it continues to operate however if the motor is stopped and restarted, it movement operate.

Does a similar thing happen to a rectifier.
Specifications of rectifier:
Input voltage : 3.3kV
Output voltage: 3kV direct current

 

[jwerthman]

Loss of one incoming phase on a 3-phase rectifier will result in the remaining two phases increasing to approximately 173% of full load current, assuming the output of the bridge remains constant. The remaining two phases will operate as a single-phase bridge rectifier. The ripple will increase noticeably also from the normal 3-phase operation.

 

[SteveKW]

Tell me I'm wrong...but your voltage will drop too!

 

[govender1]

jwertman, how do you arrive at the figure of 173% full load current?

 

[jwerthman]

For 3-phase supply, the input line current would be:

I(3phase)= P/(V x sqrt(3))

For the same output power, with 1-phase supply, the input line current would be:

I(single phase) = P/V

I(single phase)/I(3phase) = sqrt(3)

It's the same situation as single-phasing a 3-phase motor. This assumes that the DC load is the same on the output. The output voltage may drop, and if it does then the output power would also be reduced and the input current would be less.