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Thermal Protector SZ1

Power class: 1,6 A to 7,5 A
Type series: Z1

  • normally closed
  • resets automatically
  • with connector cables
  • Mylar®-Nomex®
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Thermal Protector SZ1
Thermal Protector SZ1
Thermal Protector SZ1
Thermal Protector SZ1

The switchgear of type series Z1 is fixed in a positive lock and is self-aligning between the floor of a conductive housing (1) and a contact cap which is made of steel (2) and insulated from it, plus an integrated stationary silver contact (6) which closes the housing like a button cell. 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) by exercising consistent, steady contact pressure. The bimetallic disc (5) is held on the one movable contact (4) which sticks out through this without having to be welded or fixed. As such, it can continually work (exposed). 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. If the ambient temperature now falls, the bimetallic disc (5) snaps back into its start position when reaching the defined reset temperature and the contact is closed again. As a result of the aluminium oxide-based semiconductor connected in series (7) with a defined series resistance, the switchgear is heated externally depending on the operating current and shutdown. As a result of this design, it is no longer necessary to connect the Thermal protectors to the potential heat source of the device to be protected. Such Thermal protectors are often applied equally effectively at other places in the device to be protected.

Technical specifications

Nominal switching temperature (NST) in 5°C
70 °C - 160 °C
Tolerance (standard)
±5 K
Reverse switch temperature (RST)
≥ 35° C
≥ 35° C
(defined reset temperature possible on customer request)
Installation height from
5.0 mm
9.5 mm
Length of the insulation cap
18.0 mm
Resistance to impregnation
Series resistor for setting the current sensitivity
0.12 Ω - 70.00 Ω
Suitable for installation in protection class
Standard connection
Lead wire 0.25 mm² / AWG22
Operating voltage range AC / DC
up until 500 V AC / on request
Rated voltage AC
250 V (VDE) 277 V (UL)
Rated current AC cos ϕ = 1.0 / cycles
2.0 A / 3,000
Rated current AC cos ϕ = 0.6 / cycles
1.6 A / 3,000
Max. switching current AC cos ϕ = 1.0 / cycles
4.0 A / 3,000
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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