Description
- Model: Eaton MPB2-TP (Cutler-Hammer)
- Brand: Eaton / Cutler-Hammer
- Series: Power Buffer / Motor Protection Series
- Core Function: Provides a voltage buffer/ride-through for control circuits during power dips
- Product Type: Power Buffer Module
- Key Specs: 24V DC Nominal | Panel Mount | Transient Protection
- Input Voltage: 24V DC (Range: 18V – 30V DC)
- Output Voltage: Follows input (buffered)
- Holdup Time: Typically 100ms – 500ms (depending on load)
- Mounting: DIN-rail or backplane surface mount
- Terminals: Screw-type compression terminals
- Internal Storage: High-capacitance energy storage
- Status Indication: Power LED (usually Green)
- Protection: Reverse polarity and over-voltage protection
- Operating Temp: -25°C to +60°C
- Enclosure Rating: IP20
Application Scenarios & Pain Points
In industrial motor control centers (MCCs), a momentary voltage sag (brownout) can cause contactors to “chatter” or drop out, leading to an unplanned motor trip. The Eaton MPB2-TP acts like a tiny UPS (Uninterruptible Power Supply) specifically for the control coil or the protection relay logic. If your system is tripping during heavy equipment startups elsewhere in the plant, this buffer is the hardware solution that keeps the “brains” of the motor starter alive through the dip.
Typical Application Scenarios:
- Motor Protection Relays: Providing backup power to the MP-3000 or similar relays so they don’t reset during a voltage sag.
- Critical Contactors: Preventing large AC contactors from dropping out during utility switching events.
- PLC Remote I/O: Keeping a remote I/O rack powered long enough to communicate a “controlled shutdown” if main power fails.
- Pumping Stations: Ensuring that control logic stays active during the high-current inrush of massive pump motors.
Real-World Case: The “Mid-Summer” Nuisance Trip
Background: A wastewater treatment plant experienced random motor trips every afternoon during the summer. The logs showed “Control Power Loss,” but the main breakers never tripped.
Problem: The facility was at the end of a long utility line. When the neighboring industrial park’s HVAC systems all kicked in at 2:00 PM, the local voltage would dip for about 150ms. It wasn’t enough to stop the motors, but it was just enough to make the 24V control relays drop out.
Solution: We installed Eaton MPB2-TP modules in the critical starter buckets. These modules provided the 200ms of “ride-through” needed to bridge the utility sag.
Result: The nuisance trips stopped immediately. Pro Tip: If you’re seeing “Unexplained Resets” on your motor protection displays, don’t blame the relay—check the 24V stability. Adding a buffer is much cheaper than upgrading the entire plant’s power conditioning.
EATON MPB2-TP
Compatible Replacement Models
Eaton and Cutler-Hammer have integrated many of these functions into newer smart-starters, but the MPB2-TP remains a vital spare for existing MCCs.
| Model | Series | Compatibility | Note |
| MPB2-TP | Power Buffer | ✅ Exact Match | 24V DC version |
| MPB1-TP | Power Buffer | ❌ Incompatible | 120V AC version (do not mix!) |
| PXM-BUFFER | Power Xpert | ⚠️ Limited | Modern equivalent for Power Xpert meters |
Engineer’s Note: The “-TP” suffix usually indicates “Transient Protection.” If you find a version without the suffix in an old cabinet, the MPB2-TP is a superior, fully compatible upgrade.
Troubleshooting Quick Reference
| Symptom | Possible Cause | Correlation | Quick Check | Action |
| LED is OFF | No Input Power | ✅ High | Measure 24V DC at the input terminals. | Check upstream fuse or power supply. |
| LED is ON, but relay trips | Load too high | ⚠️ Medium | Calculate the total Amp-draw of the connected devices. | Reduce load or add a second MPB2-TP. |
| Short Circuit Trip | Internal Cap Failure | ⚠️ Medium | Disconnect output and see if the fuse still blows. | Replace the MPB2-TP module. |
| “Chattering” during sag | Buffer Exhausted | ✅ High | Check age of module; internal caps can dry out after 10 years. | Replace with a new module. |
Final Tech Note: These modules contain large capacitors. Even after you turn off the power, wait at least 60 seconds before touching the terminals, or you might get a surprising 24V “bite.”
EATON MPB2-TP
Inventory List: Eaton & Cutler-Hammer Controls
- MPB2-TP (24V DC Power Buffer)
- MP-3000 (Motor Protection Relay)
- IQ-200 (Power Meter)
- E71-COP-CA (Photoelectric Sensor)
- HMX04231NAP6 (HVX 9000 VFD)
- C25DNF340A (Definite Purpose Contactor)
- ELC-PS01 (ELC Series Power Supply)
- A200M1CAC (Size 1 Starter)
- EMRL-1-600-1 (Voltage Relay)
- D26MR80A (Relay 4-Pole)
