Key Technical Specifications
- Product Model: TKMA31000WL
- Manufacturer: GE Industrial Solutions
- Product Type: CBMC (Circuit Breaker Molded Case)
- Pole Configuration: 3-Pole
- Rated Current: 400 Amperes
- Voltage Rating: 600VAC
- Trip Unit: Thermal-Magnetic
- Mounting Style: Plug-In / Draw-Out (WL Suffix)
- Frame Size: TKMA Series Frame
- Interrupt Rating: Verify specific kAIC on nameplate for application voltage
Product Introduction
I’ve pulled more than my share of these GE TKMA31000WL breakers out of dusty MCCs in steel mills and refineries. It’s a workhorse 3-pole, 400A molded case breaker designed for 600VAC systems, and honestly, the thermal-magnetic trip unit inside is simple enough that you can usually tell if it’s cooked just by looking at the case discoloration. The “WL” suffix tells me you’re dealing with a plug-in or draw-out style, which is a blessing when you’re trying to swap a unit under a tight shutdown window without rewiring the bus.Engineers keep specifying this frame because it handles the inrush of big motors without nuisance tripping, provided you’ve sized it right. I’ve seen these run for twenty years in 50°C ambient heat without a single false trip, but I’ve also seen them fail open because someone ignored a loose lug torque spec. This specific revision is mechanically solid, but treat the arc chute with respect; if it’s pitted or cracked, don’t risk it.
Quality SOP & Tech Pitfalls
The Lab Report:
Every TKMA31000WL that hits my bench gets the same treatment. First, I do a visual and counterfeit check under magnification to ensure the GE casting marks and date codes align. Then, it goes on the test rack for a primary injection test to verify the thermal trip point holds at 100% and the magnetic instant trip doesn’t wander. I check insulation resistance with a Fluke 1507 to ensure the internal bus bars aren’t tracking. Finally, I log the firmware or mechanical revision and seal it in anti-static wrap. If it fails any step, it gets scrapped. Period.The Engineer’s Warning:
Don’t just slide this TKMA31000WL in and assume it’s good. I once watched a tech install a “new” breaker without checking the bus stabs; the stabs were corroded from years of arcing, and the new breaker’s contacts didn’t seat fully. It ran hot for three days before melting the bus bar. Always clean the bus stabs with a Scotch-Brite pad and apply fresh contact grease. Also, verify the torque specs on the line and load lugs; 400A means nothing if the connection is loose.
Installation & Configuration Guide
- Pre-Installation: ⚠️ LOCKOUT/TAGOUT. Verify zero energy with a calibrated meter. Wait 5 minutes for capacitor discharge if downstream drives are present. Take a photo of the existing breaker’s position and any shunt trip or auxiliary switch wiring before touching a screw.
- Removal: Label every wire with tape, not just memory. Release the DIN clip or ratchet mechanism slowly; these springs are under tension. Inspect the bus stabs for pitting or heat discoloration while the slot is open.
- Installation: Copy all DIP switch or jumper settings from the old unit to the TKMA31000WL before insertion. This prevents 90% of “it won’t close” headaches. Align the breaker squarely and push until the mechanical latch engages with a solid click. Torque lugs to OEM spec (usually 25-30 ft-lbs for this frame, but check the nameplate).
- Power-On & Testing: Clear the area. Energize and verify voltage across the line side. Close the breaker manually; it should snap shut, not creep. Check for immediate heating with an IR gun after 15 minutes of load. Test any shunt trips or undervoltage releases immediately.
Compatible Replacement Models
| Model | Compatibility Tier | Notes |
|---|---|---|
| GE TKMA31000WL | ✅ Drop-in Replacement | Exact match. Verify “WL” suffix matches your base. |
| GE TKMA31200WL | ⚠️ Software Compatible | Same frame, 200A rating. Only use if load dropped; requires recalculating protection coordination. |
| GE TKMA836500WL | ❌ Hardware Mod Required | Different frame/amperage. Requires new bus adapters or chassis modification. Do not attempt as a direct swap. |
Frequently Asked Questions
Can I hot-swap this TKMA31000WL if the system is live?
Absolutely not. This is a 400A, 600VAC device. Pulling it under load will arc-flash the bus and likely ruin the draw-out cradle. De-energize the feeder first.Is the TKMA31000WL interchangeable with the TKMA31000 (no WL)?
No. The “WL” indicates the plug-in/draw-out hardware interface. A fixed-mount breaker won’t physically seat in a draw-out cradle, and forcing it will crack the housing or bend the bus stabs.How do I know if the thermal element is weak?
If you’re getting nuisance trips at 70-80% load but the motor amps are fine, the thermal element has likely fatigued. You can verify this with a primary injection test kit. Don’t just crank up the trip setting to compensate; replace the TKMA31000WL.Does this come with the shunt trip installed?
Not always. The base TKMA31000WL is often sold as a bare frame. Check the specific listing or nameplate for “ST” or “SHT” designations. If you need it for ESD logic, verify the coil voltage (24VDC vs 120VAC) before ordering.What’s the torque spec for the load lugs?
For this 400A frame, it’s typically 25-30 ft-lbs, but I’ve seen older units spec’d at 20 ft-lbs. Always read the torque label on the side of the breaker. Overtightening strips the aluminum bus bar threads, and you’re back to square one.Can I use this in a panel rated for 65°C ambient?
Check the derating curve. At 65°C, a 400A breaker might need to be derated to 350A or less. If your load is constant 380A, this TKMA31000WL will eventually trip on thermal overload. Upsize the frame if ambient is that high.
