35mm mounting hole three phase circuit breakers, used for three phase 225-300KVA Pole Mounting high performance transformers. CSP oil immersed low voltage circuit breaker is installed on the secondary winding of the transformer,uses oil for insulation and arc extinction to protect electrical systems from faults.
| Model | T3P2X420T110 |
| Rated Current | 840A |
| For Transformer | 300KVA |
| Rated Voltage | 208V/120V |
| Trip Temp. | 110℃, 120℃, 130℃ |
| Phase | 3F |
| Mounting Hole Diameter | 35mm |
| Mounting Surface | CURVED/FLAT |
It is three phase circuit breakers, used for three phase transformers. Circuit breaker are installed on the secondary winding of the transformer, are used for over load protection and short circuit protection.
| Model | Current (A) | Rating (KVA) | Voltage (V) | Signal light | Emergency switch (overload) | Magnetic protection | Resistance (Ω) at 25°C 2 poles | Loss (W) at 85°C 2 poles |
|---|---|---|---|---|---|---|---|---|
| T3P2X313TXXX | 626 | 225 | 208/120 | Yes | Yes | Yes | UΩ | 155 |
| T3P2X420TXXX | 840 | 300 | 208/120 | Yes | Yes | Yes | UΩ | 270 |
| Max Voltage | Power Frequency Test (one minute) 50/60HZ | Lightening Impulse Test | Insulation Resistance (5000V) | Normal Interrupting Capacity |
|---|---|---|---|---|
| 600V | ≥10KV | 30KV | ≥5000MΩ | 11KA~20KA |
| Model | Current (A) | Interrupting Capacity(KA) |
|---|---|---|
| T3P2X313TXXX | 626 | 20KA |
| T3P2X420TXXX | 840 | 20KA |
(Trip temperature = Bi-metal trip temperature)
| No. | Bimetal ID | Current (I: A) | Bi-metal Ampere Response Factor (J: °C/A²) | Bi-metal temperature rise to oil (ΔT: °C) | Oil temperature (To: °C) | Bi-metal temperature (T: °C) |
|---|---|---|---|---|---|---|
| 01 | 626 | 626 | 0.0000610 | 6.0 | To | 6.0+To |
| 02 | 840 | 840 | 0.0000720 | 12.5 | To | 12.5+To |
T:Bi-metal temperature(℃ )
ΔT:Bi-metal temperature rise to oil(℃ )
To:oil temperature(℃)
I:Current flow through the Bi-metal trip in(A)
J:Bi-metal Ampere Response Factor in (J:℃ /A²)
ΔT=I²*J
T= ΔT+To
Note: When Bi-metal temperature reaches the trip temperature setting of the breaker,the breaker trip.
The following drawings show only partial product dimensions.
For the complete set of engineering drawings or full specifications, please contact us at [📪nancywang@ketranele.com].


Q1: Do you have American-style 35mm mounting hole three phase CSP circuit breaker for 600kVA transformer?
A1:Yes, we are the source factory for CSP oil-immersed breaker,can provide the protection device for your large distribution transformer.
Q2:How often should an oil-immersed CSP breaker be serviced?
A2:Recommended to perform oil sampling and mechanical inspections every 3 to 5 years. Under normal operating conditions, these CSP breakers require very little maintenance.
Q3:How to install three phase CSP circuit breaker for 600kVA transformer?
A3: We have the video for oil-type CSP circuit breaker in Ketran Youtube website: https://www.youtube.com/@oilimmersedcircuitbreakerf2698
Q4:What is your MOQ ?
A4: For this large oil type distribution transformer circuit breaker, 5 units is the MOQ .