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solid-state contactor and SITOR fuse

Created by: ionut.b at: 3/26/2009 11:27 PM (3 Replies)

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3/26/2009 11:27 PM	Rate (0)
ionut.b Posts: 289 Rating: (3)	I have a heater with three heating resistances: current of 33A at a supply voltage of 230 VAC. For this I have choosed the following: solid-state contactor: 3RF2350-1AA02 (24VDC command, 50A, 230VAC) current monitor: 3RF2950-0GA13 fuse: SITOR : 3NC1440 (40A) Afther two days of problems free function, two of the fuses have been blown (an interval of 8 hours). According to the technical catalogue I have choosed a 50A contactor for a 33 A current. But instead of a 50 A fuse I have choosed a 40A fuse. When running, the fuses are getting hotter (40-50 degrees). Should a choose to go with 50A fuse even for a 33A current? Would the solid-state contactor still be corectely protected? Thank you.
ionut.b Posts: 289 Rating: (3)
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3/31/2009 9:39 AM	Rate (0)
LesPaul Posts: 467 Rating: (59)	hello ionut.b the sitor fuse is only to use for short circuit protection, not foroverload protection She can constantly be charged to 40 A. After characteristicshe cannot be used withfurther load, she will be thermal destroyed. The current probably lies higher than 40 A. We recommend using 3NC1450. Kind regards
LesPaul Posts: 467 Rating: (59)
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3/31/2009 1:40 PM	Rate (0)
ionut.b Posts: 289 Rating: (3)	Hello LesPaul. I am only using the fuse as an short-circuit protection of the solid-state contactor. The heater has three heating elements (230VAC), each with it's own semiconductor contactor. Cable 10mm2. Canthe electric heater be overloaded? I think it can only be short-circuited with ground or simply wire-brake. I am measuring the current with a FLUKE current clamp and i get a value around 33A. I don't see how the meassured current can be wrong. This is the reason why I have choosed a 40A fuse. The contactors are not in a PID loop. They are actuated at a frequency bigger than 1Hz. As I said earlier the fuse is getting hotter (in 10-15 minutes after start). Two of the fuses are blown, on different phases and at different intervals. If I try with a 50A SITOR fuse, it should have a lower temperature than a 40A. The protection for the solid-state contactor(In=50A ) is still ok with a 50A fuse ? Can it be other explanation than the current being so close to 40A? Like external power supply factors, types, etc. Thank you.
ionut.b Posts: 289 Rating: (3)
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11/30/2017 2:47 PM	Rate (0)
Jen_Moderator Posts: 8171 Rating: (174)	New question published by BATTISTAS. is split to a separate thread with the subject Where can find the electrical diagram to connect and protect the 3RF solid state converter?. Best regards Jen_Moderator
Jen_Moderator Posts: 8171 Rating: (174)
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