Automotive LC-4 DC Brushless Motor Controller Debugging and Fault Diagnosis Guide

On site testing method:

Adjust the current limiting potentiometer to a lower value (such as 30% of the rated current), then gradually increase the load (such as mechanical locking or increasing friction), and observe whether the current is clamped near the set value. If the current is stable and does not continue to rise, it indicates that the limiting function is normal.

3.2 Overtemperature tripping

The temperature of the power stage (MOSFET or IGBT) is monitored by an internal thermistor. When the temperature of the radiator exceeds the threshold (usually around 80-90 ° C), the controller shuts down the output stage and lights up the fault LED. After the temperature drops by about 10 ° C, the controller automatically resets (requiring a restart signal).

Common reasons:

Poor ventilation (high temperature inside the cabinet)

Continuous overload operation

Dust accumulation on the heat sink

The ambient temperature exceeds the rated value

Exclusion measures:

Improve heat dissipation (increase fans), reduce load cycles, and clean dust.

3.3 Overvoltage/undervoltage tripping

DC bus voltage monitoring:

Undervoltage: usually<80V DC (corresponding to low AC input or power fluctuation)

Overvoltage: usually>180V DC (corresponding to AC input being too high or regenerative energy)

For LC-4 (single quadrant), regenerative energy cannot be fed back to the grid. If the motor is dragged by external forces (such as downhill or emergency stop) to become a generator, the bus voltage will rise, triggering overvoltage protection. At this point, external braking resistors or mechanical braking are required.

3.4 Blocked rotor protection

When the motor speed command persists but the actual speed is zero (or extremely low) for more than the set time (usually a few seconds), the controller determines that it is stuck, shuts off the output, and gives a fault indication. This prevents the motor coil from overheating and insulation damage.

Attention: During the debugging phase, if the motor does not rotate due to wiring errors, it may also trigger the locked rotor protection. The wiring of the motor Hall/encoder should be checked first.

3.5 MOV protection circuit

MOV is connected in parallel at the AC input terminal to absorb surges. But MOVs will age (increase leakage current) after multiple surges. It is recommended to regularly (such as annually) check the input current or replace the built-in MOV module in areas with frequent lightning strikes.

Operation characteristics and application wiring

4.1 Simulated speed control

LC-4 accepts multiple simulated speed command formats:

0-5V (single ended)

0-10V (single ended)

4-20mA (requires external resistor)

External potentiometer (10k Ω, connected to+5V reference voltage)

Wiring diagram:

Connect the signal ground (Analog Common) to the AGND terminal of the controller

Command signal connected to SPEED REF IN

Adjustment: Two fixed speeds can be preset through the internal potentiometer "Velocity Set Point 1" and "2", and the electronic gear function (such as high-speed operation and low-speed positioning) can be achieved by switching between the two through the digital input "Dual Speed Select".

4.2 External start stop, forward and reverse rotation, dynamic braking

Input signal function logic

START/STOP: High level operation, low level parking

FORWARD/REVERSE direction control: high level forward, low level reverse (or opposite)

When the dynamic brake is at high level, the motor winding is short circuited to achieve quick stop

Attention: Dynamic braking stops faster than downhill deceleration, but generates a larger current. It should be used in conjunction with current limiting.

4.3 External PWM Input

LC-4 can directly receive external PWM signals (usually with a frequency of 1-10 kHz and a duty cycle of 0-100%) as speed commands, eliminating the need for D/A conversion. This function is convenient for direct interface with PLC or microcontroller.

Wiring: Connect the PWM signal to the PWM IN terminal and the signal ground to AGND.

Configuration: The speed command selection switch needs to be set to "PWM" mode.

4.4 Diagnostic LED

The LED on the panel indicates the following status:

POWER (green): Auxiliary power supply is normal

RUN (green): The motor is running (PWM output enabled)

Fault (red): Fault status (over temperature, over voltage, under voltage, locked rotor, etc.)

Current Limit (flashing yellow): Currently in current limiting state

Detailed explanation of adjustment items and closed-loop debugging

5.1 Soft Start

Adjusting this potentiometer can set the time required for the motor to accelerate from zero speed to a given speed. Typical range is 0.1-10 seconds.

On site technique: For loads with high inertia, increase the soft start time appropriately to avoid triggering the limit due to the impact of starting current.

5.2 Tachometer Gain

When using a speed generator as speed feedback, it is necessary to adjust this potentiometer to match the feedback voltage inside the controller with the actual speed.

Calibration method:

Given a fixed speed command (such as 5V).

Measure the actual speed of the motor with a tachometer.