chinese VFD blow out


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    Default chinese VFD blow out

    Hi,

    I am finishing a self designed CNC mill. It has a chinese spindle and 2.2kW Huanyang VFD bought as a pair.

    Basic testing has been going well and I wanted to make an aluminium piece to hold a ballnut. Surfacing the block went well and provided a very satisfactory finish. I went to cut the 28mm central hole with a 8mm 4 flute end mill. The first cut was 1mm and then 2mm each time down to 30mm.

    The 1mm cut went well but as it got into the second but where it was biting a bit more material there was a pop and flash from the connector going into the spindle. Presumably a short to ground since this tripped the differential and the 6A trip switch. ( 6A may have been a bit light, I had a 16A in there too and seem to have connected then to the wrong cct ).

    I slowly powered things back up intending to withdraw the tool with manual commands the the GCODE interpreter. When I reset the trip feeding the VFD, there was a crackle and healthy coil of smoke !

    Examination of the spindle connector shows blackening due to the arc but no obvious short. For the moment I am guessing that something is a bit too close when assembled and as I was pulling more load with the heavier cut, the VFD voltage rose higher than before causing an arc. The arc may have triggered a high voltage back EMF which took out some components in the VFD. When I powered it back up ( supposedly in a stopped state ) it went into a fault condition which burned out some key components.

    It is probably not worth stripping the VFD to envisage repair, it was fairly crackling in the second before I cut the trip switch, but I would like to know as much as possible about what occurred to avoid a repeat performance when I get a new controller.

    The circuits look well made but that does not mean they are not cutting corners with protection circuits to cut costs. If my guesses at the sequence of events are correct I would have expected the drive to be protected against spikes coming back from the motor and obvious fault conditions like a short circuit on the output.

    Does anyone have any experience of these Huanyang VFD controllers going wrong?


    Thanks for any info.

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    Last edited by reg.miller; 08-12-2019 at 01:19 PM.


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    Default Re: chinese VFD blow out

    Have you disconnected the VFD output completely and powered up and checked the display for any fault reading etc.
    If not, try this and see what the result is.
    If you are lucky, it may be just defective wiring/connections etc.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: chinese VFD blow out

    Quote Originally Posted by reg.miller View Post
    Hi,

    I am finishing a self designed CNC mill. It has a chinese spindle and 2.2kW Huanyang VFD bought as a pair.

    Basic testing has been going well and I wanted to make an aluminium piece to hold a ballnut. Surfacing the block went well and provided a very satisfactory finish. I went to cut the 28mm central hole with a 8mm 4 flute end mill. The first cut was 1mm and then 2mm each time down to 30mm.

    The 1mm cut went well but as it got into the second but where it was biting a bit more material there was a pop and flash from the connector going into the spindle. Presumably a short to ground since this tripped the differential and the 6A trip switch. ( 6A may have been a bit light, I had a 16A in there too and seem to have connected then to the wrong cct ).

    I slowly powered things back up intending to withdraw the tool with manual commands the the GCODE interpreter. When I reset the trip feeding the VFD, there was a crackle and healthy coil of smoke !

    Examination of the spindle connector shows blackening due to the arc but no obvious short. For the moment I am guessing that something is a bit too close when assembled and as I was pulling more load with the heavier cut, the VFD voltage rose higher than before causing an arc. The arc may have triggered a high voltage back EMF which took out some components in the VFD. When I powered it back up ( supposedly in a stopped state ) it went into a fault condition which burned out some key components.

    It is probably not worth stripping the VFD to envisage repair, it was fairly crackling in the second before I cut the trip switch, but I would like to know as much as possible about what occurred to avoid a repeat performance when I get a new controller.

    The circuits look well made but that does not mean they are not cutting corners with protection circuits to cut costs. If my guesses at the sequence of events are correct I would have expected the drive to be protected against spikes coming back from the motor and obvious fault conditions like a short circuit on the output.

    Does anyone have any experience of these Huanyang VFD controllers going wrong?


    Thanks for any info.
    This used to be a regular problem with smoked Drives and spindles I used to repair them if they where not to badly smoked

    Parameter settings if set correct usually protect the VFD Drive from most problems like this, a dead short though can take out anything in it's path

    I recommend to wire direct to these spindles which is not hard to do and you are sure then of a good connection and no possible way of any shorts happening with in the spindle plug, if the plugs have the correct size cable, there is not normally a problem though

    Mactec54


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    Default Re: chinese VFD blow out

    Thanks, I have opened the VFD and it appears that one of a pair of high power wound resistors was getting hot and melted the plastic casing of an adjacent relay. I think I got there quick enough that neither of these if fatally wounded. However, I think that the fact that this is happening on power-on is a sign that something in the control circuit has been damaged.

    It could be that a power semiconductor like a IGBT has gone short circuit and could be fairly easily replaced, however, without the slightest schematic, I fear it is more effort than it is worth. I'm a little surprised that it was not better protected, since it does look like a good product on visual inspection.

    My main problem is to ascertain what happened in the spindle to provoke the failure, in order to ensure it does not happen again if I replace the VFD.



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    Default Re: chinese VFD blow out

    Quote Originally Posted by reg.miller View Post
    Thanks, I have opened the VFD and it appears that one of a pair of high power wound resistors was getting hot and melted the plastic casing of an adjacent relay. I think I got there quick enough that neither of these if fatally wounded. However, I think that the fact that this is happening on power-on is a sign that something in the control circuit has been damaged.

    It could be that a power semiconductor like a IGBT has gone short circuit and could be fairly easily replaced, however, without the slightest schematic, I fear it is more effort than it is worth. I'm a little surprised that it was not better protected, since it does look like a good product on visual inspection.

    My main problem is to ascertain what happened in the spindle to provoke the failure, in order to ensure it does not happen again if I replace the VFD.
    What Parameters did you have set did you keep a list of what you set this is important

    The first thing you can do a quick test of the spindle with your meter

    measure
    Pin 1 to Pin 2=

    Pin2 to Pin3=

    P3 to Pin 1=

    Pin 4 to the spindle Body

    And then all the pins to Ground which is spindle Body

    Mactec54


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    Default Re: chinese VFD blow out

    Quote Originally Posted by mactec54 View Post
    What Parameters did you have set did you keep a list of what you set this is important

    The first thing you can do a quick test of the spindle with your meter

    measure
    Pin 1 to Pin 2=

    Pin2 to Pin3=

    P3 to Pin 1=

    Pin 4 to the spindle Body

    And then all the pins to Ground which is spindle Body
    Thanks for the reply. The soot marks inside the connector body indicate one phase shorted to ground. This is also borne out by the fact the differential trips went as well as the current trip. Pin4 goes nowhere ! For some reason the Chinese do not link this to anything in the motor. It's a dud. This means I have to rely on the body grounding via its mounting.

    Each terminal pair shows 1.6 ohm static resistance and no connection to ground.

    I have coated the soldered terminal pins with PU mastic to ensure there is more than just air between wires and connector shell.

    Last edited by reg.miller; 08-13-2019 at 11:02 AM.


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    Default Re: chinese VFD blow out

    The Chinese never seem to use Pin 4 as intended.... motor frame ground. That means unless you had a ground wire from your control panel directly connected to the motor housing like I do, the fault current went through your Z axis bearings or others. So they might be damaged.

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


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    Default Re: chinese VFD blow out

    Quote Originally Posted by reg.miller View Post
    Thanks for the reply. The soot marks inside the connector body indicate one phase shorted to ground. This is also borne out by the fact the differential trips went as well as the current trip. Pin4 goes nowhere ! For some reason the Chinese do not link this to anything in the motor. It's a dud. This means I have to rely on the body grounding via its mounting.

    Each terminal pair shows 1.6 ohm static resistance and no connection to ground.

    I have coated the soldered terminal pins with PU mastic to ensure there is more than just air between wires and connector shell.
    The Chinese are the only country in the world that don't always connect a Ground but anywhere else in the world you have to wire use a Ground connection

    You have to use a 4 wire shielded cable from the VFD Drive to the Spindle

    So you never connected the 4th pin to the spindle body, this is a must do, the Ground is a very important part of this connection, the Ground wire mounted to the spindle body works also if you can't connect it any other way

    Mactec54


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