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Elevator Boost Transformer

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Scozadd

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Topeka
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Project Manager
The engineer has the breaker at 60a but the transformer was sent from factory with 20a fuses on the primary. We switched those out for 50a from the secondary and it blows those instantly. I'm sure it needs bigger fuses, just not sure how much bigger. Waiting on response from engineer. Neither Jefferson transformer or Schindler are any help.
 
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jim dungar

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Wisconsin
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PE (Retired) - Power Systems
Scozadd said:
The engineer has the breaker at 60a but the transformer was sent from factory with 20a fuses on the primary. We switched those out for 50a from the secondary and it blows those instantly. I'm sure it needs bigger fuses, just not sure how much bigger. Waiting on response from engineer. Neither Jefferson transformer or Schindler are any help.
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Contact your fuse supplier. It should take just a few minutes to look at a fuse curve. For inrush situations, I prefer type RK5 fuses as they are often a little slower than RK1s.
 
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GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
Scozadd said:
The engineer has the breaker at 60a but the transformer was sent from factory with 20a fuses on the primary. We switched those out for 50a from the secondary and it blows those instantly. I'm sure it needs bigger fuses, just not sure how much bigger. Waiting on response from engineer. Neither Jefferson transformer or Schindler are any help.
Click to expand...
The fuses on the secondary do not have to handle the connection inrush, so their time delay characteristic is probably wrong for use on the primary side. Contact your fuse supplier as Jim suggested, and/or look at the fuse type of the 20A fuses which were originally installed and match it.
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The rated input current of this transformer is 89A, and the nameplate specifically says that the maximum primary OCPD is 150A.

What is the reason for 20A or even 60A _primary_ fusing?

-Jon
 
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