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Thermal Protector KP1

Power class: 1,6 A to 7,5 A
Type series: P1

  • normally closed
  • does not reset automatically
  • with connector cables
  • Mylar®-Nomex®
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Thermal Protector KP1
Thermal Protector KP1
Thermal Protector KP1

The switchgear of type series P1 is fixed in a positive lock and is self-aligning between the floor of a conductive housing (1) and a PTC cap made from barium titanate (2) which sticks out from a stationary silver contact (6). At the same time, the spring snap-in disc (3) which forms the current transfer element bears the movable contact (4) and discharges the flow of current and self-heating from the bimetallic disc (5). The bimetallic disc (5) is held on the movable contact (4) which sticks out through this without having to be welded or fixed. When the rated switching temperature is reached, the bimetallic disc (5) snaps into its inverted position and pushes the spring snap-in disc (3) downwards. The contact is abruptly opened and the temperature rise of the device to be protected is disrupted. The PTC resistance (2) connected in parallel now sustains the operating voltage and deploys a defined electrical heating output on the bimetallic disc (5) regardless of the ambient temperature and permanently sustains it above its springback temperature so that the switch gear cannot reset. The contact remains open. The Thermal protectors can only cool down again and switch to the original closed state when the external operating voltage is no longer applied and/or disconnection from the mains.

Technical specifications

Nominal switching temperature (NST) in 5°C
60 °C - 180 °C
Tolerance (standard)
±5 K
Reverse switch temperature (RST)
≥ 35 °C
≥ 35 °C
(defined reset temperature possible on customer request)
Installation height from
4.9 mm
9.5 mm
Length of the insulation cap
13.0 mm
Resistance to impregnation
Suitable for installation in protection class
Standard connection
Lead wire 0.25 mm² / AWG22
Operating voltage range AC
from 115 V to 250 V AC
Rated voltage AC
250 V (VDE) 277 V (UL)
Rated current AC cos ϕ = 1.0 / cycles
2.5 A / 1,000
Rated current AC cos ϕ = 0.6 / cycles
1.6 A / 1,000
Max. switching current AC cos ϕ = 1.0 / cycles
10.0 A / 1,000
Max. switching current AC cos ϕ = 0.6 / cycles
6.3 A / 1,000
High voltage resistance
2.0 kV
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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