Kepco BOP 1000M Troubleshooting Application

Kepco BOP 1000M Four Quadrant Power Supply Complete Guide

Introduction: Why Four Quadrant Power Supply is the Key to Complex Load Testing

In fields such as motor drive, battery simulation, solar panel characterization, magnet excitation, and power quality testing, engineers often face a tricky problem: the load not only draws energy from the power source, but also feeds back energy to the power source under certain operating conditions. Traditional single quadrant DC power supplies cannot absorb reverse current and can only consume this energy through parallel high-power resistors or electronic loads, which not only has low efficiency but also has complex systems and severe heating.

The Kepco BOP (Bipolar Operational Power Supply) series of four quadrant power supplies fundamentally solves this contradiction. The BOP 1000M (i.e. BOP 1KW series) adopts a switch type topology with built-in bidirectional power factor correction (PFC) circuit. It can seamlessly switch to sink in the second and fourth quadrants while outputting power as a source, and feed back the absorbed energy to the grid with an efficiency of over 65%. This article is based on the official technical information of Kepco, systematically sorting out the technical characteristics, selection points, and common troubleshooting methods of BOP 1000M and the entire BOP family, providing a complete practical manual for engineers who are evaluating or using this series of power supplies.

Chapter 1: Four quadrant working mode and energy feedback principle

1.1 The meaning of the four quadrants

Conventional DC power supplies can only operate in the first quadrant (positive voltage, positive current), providing power to the load. The BOP series can work in any of the four quadrants:

First quadrant (+V,+I): The power supply serves as the source and outputs power in the forward direction.

Third quadrant (- V, - I): The power supply serves as the source and outputs power in reverse (outputting negative voltage and current).

Second quadrant (+V, - I): voltage is positive, current is negative - the power source absorbs power, equivalent to an electronic load.

Fourth quadrant (- V,+I): Voltage is negative, current is positive - the power source also absorbs power.

This feature enables it to perfectly drive inductive or capacitive loads, such as feeding back energy during motor deceleration, battery discharge testing, or charging and discharging cycles of capacitive loads.

1.2 Bidirectional PFC and Energy Feedback

When traditional linear BOPs (200W/400W) are used as absorbers, the internal linear adjustment tubes dissipate energy in the form of heat, so their rated absorption current is usually only half of the source current (e.g. 10A source, 5A absorption). The switch type BOP 1KW (1000W series) is completely different: its input terminal adopts a patented bidirectional power factor correction circuit. When BOP is in source mode, PFC converts the AC input into a stable DC bus voltage; When the BOP is in absorption mode, the PFC circuit works in reverse, reversing the energy feedback from the load back to the AC power grid, and the power factor is still as high as 0.97. This means:

No need for external braking resistors or electronic loads;

Long term continuous power absorption (such as battery discharge testing) will not cause equipment overheating;

The overall efficiency can reach 65%~70% in source mode (slightly lower in low-voltage models), and is close to the same level in absorption mode.

Practical operation and maintenance reminder: When connecting active loads (such as batteries, generators), it is necessary to ensure that the steady-state voltage of the active load does not exceed the maximum rated voltage of the BOP. For example, the voltage range of BOP 100-10MG is ± 100V. If a 110V battery is connected, the overvoltage protection (OVP) will immediately turn off the output. This is one of the most common faults on site.

Chapter 2: Detailed Explanation and Selection Points of BOP 1KW Series Models

2.1 MG Standard Type (Universal Switch Type)

The BOP 1KW MG series covers 8 voltage/current combinations ranging from ± 6V/± 125A to ± 100V/± 10A, with specific parameters as follows (according to the datasheet):

Model Voltage Range Current Range Voltage Channel Gain Current Channel Gain Series Resistance (m Ω) Series Inductance (μ H)

BOP 6-125MG ±6V ±125A 0.6 12.5 0.05 1.5

BOP 10-75MG ±10V ±75A 1.0 7.5 0.13 2.0

BOP 20-50MG ±20V ±50A 2.0 5.0 0.40 8.3

BOP 36-28MG ±36V ±28A 3.6 2.8 1.30 25.6

BOP 50-20MG ±50V ±20A 5.0 2.0 2.50 50.0

BOP 72-14MG ±72V ±14A 7.2 1.4 5.14 104.0

BOP 100-10MG ±100V ±10A 10.0 1.0 10.0 163.0

When selecting, it should be noted that the series resistance of low voltage and high current models (such as 6-125MG) is extremely low (0.05m Ω), but the switching frequency is 50kHz, resulting in slightly lower efficiency (56%); High voltage models (100-10MG) have a switching frequency of 70kHz and an efficiency of 65%. For high impact loads such as solenoid valves and motor starting, it is recommended to choose a current margin of at least 1.5 times the peak current.

2.2 GL ultra-low ripple type (optimized inductive load)