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●The brake of main motor

Main motor brake operation:

The brake status is following the main motor action.

If motor power off, the brake is ON /work.If motor power on, the brake will release, then motor running.


Y2 relay on main motor is designed for “easy to change the motor belt”, it could control brake release under motor stop status.If the motor under no brake status when change belt, user can easy to change the belt.

The parameter is No. 3422.Normally No. 3422 set 0, and Y2 is not energizing. When customer need to change motor belt , it need set the parameter 3422 value at 1 , and press emergency stop button, then Y2 just emerging to open the motor brake to change the belt .

After done replacement, must go to parameter 3422 to set back 0 (NO) , then just can run the Ram normally.  

Ans .

First, check the replay of brake is working normal and without phase failure during the Ram run status.

The relay is for control the motor brake power: 

How to check relay for brake unit :


If the relay damaged, please replace it.

If replay is normal, then check following items in the order :

  1. Check the U, V,W voltage at end of motor power box :

     If it happens any phase failure due to any wire broken.

  2. If input power of motor and brake is no problem without any phase fail.

    Please separate the brake wires from main motor input, and connect input power to the brake only to check it.

    If brake input power is correct 3 phase 220V (no phase fail), normal is the brake will open while you press Ram run (power On) ,

    but if the brake can't open , it means the brake inside coil was damaged , need to replace the brake or completed motor with brake set.

  3. If brake function is no problem, and connect U,V,W 220V to brake and main motor input together,

    brake is all okay but motor still not run smoothly, it mean the main motor damaged need to replace it .


The LYN4J relay function is for user to easy change motor belt purpose only.

Usuallythis relay is not be using often when machine operate.


The possible reason to cause the LY-4NJ relay damage:

  1. The 3 wires of Motor brake connect to L1, L2, L3 don't connect well : 
    It makes the brake work under 2 wires (phase failure) possible to cause relay over current and burn.
    Take off the back-motor plate and find 3 wires for motor brake, and check the wire are connecting well or not.
  2. By use JOG function too often: 
    Usually JOG function using few times only, when first time for test cutting purpose. 
    When machine is on continue running condition, LY-4NJ reply is not use,it is connect U1, V1, W1 under normal close.
    When use JOG function, relay will work often because JOG let motor brake release and brake again, it may possible to damage the reply when using it too often by JOG function, since the current of JOG running is bigger.
    PS. If operator often use JOG is because the Ram can't stop at top position well.
    Please adjust parameter 3423-3428 to let Ram stop at top after finished cutting. 
  3. A spark eliminator SQ3 was added to reduce the big current while JOG running. 
    But if the spark eliminator damage, it's possible to let LY-4NJ easy damage.
    How to check SQ3 :
    Measure take off 3 wires from relay base then measure each two wire "Resistance" is equal (average) or not ? Normally the resistance must be equal.