Dc Fan Motor Control Circuit - Hitachi YUTAMPO Series Service Manual

4 Electrical checks of main parts
Outdoor unit

4.1.7 DC fan motor control circuit

This model is built with DC fan motor control circuit inside outdoor electrical unit.
Outdoor electrical
Smoothing capa 2A Fuse
DC300
-330V
This DC fan motor is control by outdoor microcomputer that follow the operating instruction received from indoor
microcomputer. The DC current that flow from R741 will presume actual operation speed and control the rotation to follow
the operating instruction. Based on this DC current it will detect a over current and other fan motor failure.

Fan motor speed controller during starting
Due to the interference of strong wind etc., operation movement is changed based on fan direction and rotation speed as
shown below during starting of operation.
In addition, the fair wind is define as wind that blow to outside direction using Mouth Ring part.
• At strong and contrary wind: The rotational speed is not controlled as to protect the equipment and fan will rotate
reversely depend on the wind. Automatically start when wind condition become weak.
• At contrary wind: The rotational speed is controlled in fair wind direction after it slowly reduce the speed and finally
stop.
• At fair wind: The rotational speed is controlled as it is.
• At strong fair wind: The rotational speed is not controlled as to protect the equipment and fan will rotate in the normal
direction depend on the wind. Automatically start when wind condition become weak.

Fan motor speed controller during unit operating
There is a case where fan rpm is reducing during rotating caused by interference of strong wind.
If this condition continue in long period, fan will stop rotating. (LD301 : 11 times blinking) The unit will restart according to
control as per during start (1).

Method of confirming self diagnosis LD301 lamp: 12 times blinking.
If the unit stop and LD301 on the PCB blinking 12 times (fan lock stop is detected), follow below steps to confirm it.
1 Fan lock stop is detected when something has disturb the fan rotation by inserting material into propeller fan or ice
has growing inside outdoor unit caused by snow. Remove it if found something is blocking the fan.
2 Confirmed that CN24 connector is securely inserted. Fan lock stop is detected also when connector is not properly
inserted. Please securely insert if found any disconnection.
3 Fan lock stop also can be detected where strong wind blown surrounding the unit. Please confirm after restart the
unit. (It may take few minutes to operate the compressor). It is not a malfunction of electrical unit or fan motor if the
unit run continuously after restart the unit.
4 Check fan motor condition as below procedure.
42 SMGB0135 rev.0 - 06/2020
Drive circuit
Microcomputer
DC current Id