Sinclair SCV-750EB Service Manual page 142

6.2 L10: Hardware overcurrent
Description
The current exceeds the OCP protection value (peak value) set by the hardware or receives the FO signal from the IPM

module.
After the fault, the compressor stops running. If the fault disappears after one minute, the compressor starts again.

Trigger/resume condition
The current reaches the OCP protection value

Trigger condition: The current reaches the OCP protection value.
Resume condition: The compressor shuts down after a fault, and resumes after reaching the fault exit condition one minute
later.
Reset method: Automatic recovery after reaching the fault exit condition one minute later.
 A falling edge or continuously low level of the FO signal is detected:
Trigger condition: The falling edge or continuously low electrical level of the FO signal is detected.
Recovery Condition: The FO signal turns into high level.
Reset method: Automatic recovery after reaching the fault exit condition one minute later.
Possible causes
There are impurities in the refrigerant system or the compressor is momentarily stuck, causing the current surge to trigger

OCP;
The compressor winding is short-circuited between phases, resulting in instantaneous high current to trigger OCP or FO;

The voltage of the system power supply drops or is interrupted for a short time, resulting in an instantaneous surge of

current to trigger OCP;
Condensation of the IPM module leads to a short circuit between the control pins;

System backflow;

The rotor has a certain speed when the compressor is started (commonly when a compressor has been started or the main

engine has been started, and the refrigerant drives the rotor of the compressor that is about to start when the four-way
valve is reversed);
The abnormality of the module board (Idc, OCP comparison circuit, PWM circuit, IPM, IGBT drive power circuit) causes the

control to lose step and generate a large current to trigger the OCP.
Procedure
Compressor winding and insulation failure
Drive board fault(swap the drive board to judge)
Impurities in the refrigerant system or the
compressor is momentarily stuck (noise when
Whether the unit shares power with high-power
140
L10
Report error while in standby
NO
NO
NO
running or starting)
NO
electrical appliances
Yes
Change the drive board
Yes
Change the compressor
Yes
Change the drive board
Change the compressor and
Yes
clean the system
Yes
Rectify the power supply