OTP coils

OTP coils

OTP coils

OTP coilsOTP coil consists of 16 D-shaped coils. The shape is conditioned by dimensions of the plasma cord, divertor, gauffering of toroidal magnetic field and injection requirements.

The toroidal field coil is embedded into EMS T-15 and is intended to create a toroidal magnetic field. The EMST-15 has 16 coils of this design.

The OTP coil is installed inside a stainless-steel housing. The winding material is silver containing a copper tube.

The overall dimensions of the OTP tube mounted inside the housing:

  • Height – 4764 mm;
  • Width – 2920 mm;
  • Depth – 285 mm;
  • Mass – 7500 kg;

The turn insulation, as that of the frame, are made of glass mica insulating tape and glass tape respectively. The insulation is applied to the conductor, section or a coil with epoxy compound to saturate it, then it is pressed and sintered. The sections located on the edges are machined once the insulation is sintered and beforethe frame insulation is applied, in order to get a trapezoidal form on the inner leg.

OTP coils are installed in D-shaped stainless-steel housings that looks like a steel box with several welded parts. The winding is attached via glass mica spacers mounted on the bottom, side surfaces and under the cover using a cold-curable epoxy compound.

Coil output is located in the bottom area. Output terminals are connected through non-cooled interconnect buses; there are few compensation buses with reverse current just beside them. Each set of four coils is supplied through cables connected from below.

Moreover, the inlet and outlet of the cooling water are also located down there. OTP coils are cooled down by distillated water; there are four parallel cooling lines of a coil.

Number of coils


Number of winds in coil



Silver containing copper

Conductor diameter and surface, mm

22.5*32, ⌀10.5

Copper cross-section, mm2


OTP conductor length, m


Mass of conductor, kg


Maximal current, kA


Maximal stress of the housing insulation, kW


OTP Ohmic resistance at 20 ºС, Ohm


Winding self-inductance, H


Number of parallel cooling lines


Conductor overheating at BT = 2T and shelf reaching time of 10 s, OR


Cooling water flowrate, m3/h


Pressure loss, MPa



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