US 12,334,251 B2
Current transformer and method of manufacturing the same
Yuichi Imazato, Izumisano (JP); Kazuhiro Kasatani, Izumisano (JP); and Kazusa Mori, Izumisano (JP)
Assigned to SHT Corporation Limited, Osaka (JP)
Appl. No. 17/630,283
Filed by SHT Corporation Limited, Izumisano (JP)
PCT Filed Jun. 23, 2020, PCT No. PCT/JP2020/024549
§ 371(c)(1), (2) Date Jan. 26, 2022,
PCT Pub. No. WO2021/019963, PCT Pub. Date Feb. 4, 2021.
Claims priority of application No. 2019-140979 (JP), filed on Jul. 31, 2019.
Prior Publication US 2022/0277892 A1, Sep. 1, 2022
Int. Cl. H01F 27/24 (2006.01); H01F 3/14 (2006.01); H01F 27/00 (2006.01); H01F 27/245 (2006.01); H01F 27/26 (2006.01); H01F 27/28 (2006.01); H01F 27/34 (2006.01); H01F 41/02 (2006.01)
CPC H01F 27/346 (2013.01) [H01F 3/14 (2013.01); H01F 27/008 (2013.01); H01F 27/245 (2013.01); H01F 27/263 (2013.01); H01F 41/0233 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A current transformer comprising:
a resin-made bobbin with a through hollow section, the bobbin having a primary coil and a wire-wound secondary coil; and
a core consisting of E-type cores and I-type cores provided in the hollow section of the bobbin, wherein each of the E-type cores is formed of an electromagnetic steel sheet and has three legs extending substantially parallel to each other and a connecting part connected at each end of the legs, and each of the I-type cores is formed of an electromagnetic steel sheet and has the same length as the connecting portion, wherein the E-type cores are stacked with its central leg alternately in opposite directions, and the I-type cores are placed between the connecting parts of the stacked E-type cores,
the core comprising a plurality of core components,
wherein each of the core components has an E-type core formed by press-punching an electromagnetic steel sheet and has three legs extending substantially parallel to each other and a connecting part at each proximal end of the legs, and an I-type core formed by press-punching an electromagnetic steel sheet and has the same length as the connecting part of the E-type core, the I-type core being placed on and bonded to the connecting part of the E-type core to form a one-piece structure of the E-type core and the I-type core,
wherein each of the core components is inserted into the hollow section of the bobbin from a first direction and a second direction opposite to the first direction alternately while interchanging the top and bottom of the core component to form a stack structure of the core components,
wherein the E-type core and the I-type core with end faces prepared by the press-punching process have a rounded, slope shaped, sheared surface on their corners, a sheared surface with striations formed in the thickness direction, a fractured surface with unevenness as if the steel sheet was plucked, and a jagged burrs protruding from the end face in the punching direction,
the E-type core and the I-type core of each core component are arranged such that the sheared surface and the fractured surface are opposed to each other.