ST11 Thermal protector

Power class: 1,6 A to 7,5 A

Type series: ST11

normally closed
resets automatically
with connector cables
Mylar-Nomex insulation

ST11 Thermal protector

Main parts

1) Iron cover plate 2) stationary silver contact 3) spring disc

4) movable contact 5) housing 6) bimetal disc 7) Insulating paper


Stationary silver contact are riveted with iron cover plate.; The bimetal disc and spring disc are combined by steps on the movable contact. The current passes through the stationary silver contact to the movable contact, and then connects the housing through the spring disc to form a loop.


When the circuit is normal, the movable contact is in close contact with the stationary silver contact under the pre-pressure of the spring disc. When the rated operating temperature is reached, the bimetal disc is deformed by heat, snaps into its inverted position and pushes the spring disc downwards. The contact is abruptly opened and the temperature rise of the device to be protected is disrupted.

After the circuit is disconnected, the ambient temperature begins to fall.  When it reaches the defined reset temperature, the bimetal disc and the spring disc snaps back into its start position, the contacts will close again, and the circuit returns to the conduction state.


Nominal switching temperature (NST) in 5°C
60 °C - 250 °C
Tolerance (standard)
(60-200) °C ±5K
(205-250) °C ±10K
Reverse switch temperature (RST) tolerance
≥ 35 °C (≤ 80°C NST)
-30K±15K (≥ 85°C ≤ 180° C NST)
-60K±15K (≥ 185° C ≤ 200° C NST)
120℃±15K (>200°C NST)
Length of the insulation cap
Resistance to impregnation
Suitable for installation in protection class
Pressure resistance to the switch housing
Standard connection
0.33 mm² / AWG22
Insulation voltage
2.0 kV
Available approvals
Operating voltage range AC/DC
up until 500 V AC / 14 V DC
(60-200)°C Operating temperature products
Rated voltage AC
250 V(VDE)
277 V(UL)
Rated current AC cos ϕ = 1.0 /cycles
2.5A / 10,000
Max. switching current AC cos ϕ = 1.0 /cycles
6.3 A / 3,000
7.5 A / 300
Rated current AC cos ϕ = 0.6 /cycles
1.6 A / 10,000
Rated voltage DC
12.0 V
Max. switching current DC /cycles
40.0 A / 5,000
(205-250)°C Operating temperature products
Rated current AC cos ϕ = 1.0 /cycles
2.5A / 1,000
Rated current AC cos ϕ = 0.6 /cycles
1.6 A / 1,000
Total bounce time
< 1 ms
Contact resistance
≤ 50 mΩ
Vibration resistance at 10 ... 60 Hz
100 m/s²



Sales:Don Qu

Phone:+86 183 5813 1344

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