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Thermal Protector CYH

Power class: 4,0 A to 25,0 A
Type series: YH

  • Three-pole (normally closed) for three phase AC current use in the star point
  • resets automatically
  • without insulation
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Thermal Protector CYH
Thermal Protector CYH
Thermal Protector CYH
Thermal Protector CYH

Switchgear consisting of a mobile and circumferential contact bridge (1), a contact bearing pin (2), a spring snap-in disc (3) and a bimetallic disc (4) which is riveted into one another, undetachable and fixed in a positive lock and self-aligning between the floor of a conductive housing (5) and an insulating ceramic bearing (6) with two integrated stationary contacts (7) as electrodes. At the same time, the switchgear is supported by the spring snap-in disc (3) with the contact bridge (1) acting as a transfer element for electric current which is held between a supporting collar and a circumferential ring. As such, the bimetallic disc (4) underlying it, that is also stuck out from the contact bearing pin (2), can continuously work (exposed) by mechanical loads without the contact pressure defined by the spring snap-in disc (3) diminishing. As soon as the bimetallic disc (4) reaches its rated switching temperature, it effectively springs against the throw force of the spring snap-in disc (3) into its inverted position. The contacts are abruptly opened. The temperature will now fall. The bimetallic disc (4) will only snap back upon reaching a defined reset temperature and the contacts will be abruptly closed again. As the contact bearing pin (2) is appropriately dimensioned, an easy, circular rotation of the circle-shaped contact bridge (1) is enabled with every switch so that transfer resistances remain constantly below the minimum limit after many switch cycles and the long term stability is sustained even under high levels of stress. Through an additional outer connection to the switch housing, the Thermal protectors can be operated in a threephase arrangement. In this case the current flow is interrupted during operation through each phase.

Technical specifications

Nominal switching temperature (NST) in 5°C
70 °C - 180 °C
Tolerance (standard)
±10 K
Reverse switch temperature (RST)
≥ 35 °C (≤ 95 °C NST)
-50 K ± 15 K (≥ 100 °C ≤ 180 °C NST)
≥ 35 °C
(defined reset temperature possible on customer request)
Installation height from
6.5 mm
9.0 mm
Resistance to impregnation
Suitable for installation in protection class
Pressure resistance to the switch housing
600 N
Standard connection
Lead wire 1.0 mm² / AWG18
Operating voltage range AC
up until 440 V AC
Rated voltage AC
3x 400 V 50/60 Hz
Rated current AC cos ϕ = 1.0 / cycles
2.5 A / 10,000
Max. switching current AC cos ϕ = 1.0 / cycles
12.0 A / 3,000
Total bounce time
< 1 ms
Contact resistance (according to MIL-STD. R5757)
≤ 50 mΩ
Vibration resistance at 10 ... 60 Hz
100 m/s²


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