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Brake motor/rectifier

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  • 21-07-2016 8:57pm
    #1
    minzabud
    Registered Users Posts: 247 ✭✭


    I've been working with 3phase motors for ten years but have only come across motors with brakes recently and while it's not rocket science I would like to understand the following situation better.

    I was called to a breakdown in work to find a 3phase motor supplied by 230v via an invertor tripping the circuit, I disconnected the wiring to the brake which then stopped the circuit from tripping and ended up replacing the motor for a new one which had the brake pre wired by U1 and W1 so removed the old wiring which had 230 live/neutral coming in from the contactor.

    The machine ran upon test and worked for a day and then gave an error on the invertor which again would only clear when brake wiring was disconnected, I called my boss who said it needs to wired as the old was with 230 broke through the invertor so the brake releases before the invertor kicks in, we have another of these machines with the same motor and rectifier so I checked it's wiring and it has the 230v feed instead of the U1/V1 feed, all put back together and tested it trips the circuit as soon as the contactor comes in, the machine runs at 130hz so I'm wondering if that fried the rectifier or what exactly happened?

    The rectifier was replaced and its now working, but I'm wondering about the way it was pre wired, the motor was wired in star off the shelf but I changed to delta?


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    #2
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    So, am I understanding this right?

    You have a contactor feeding an inverter. Presumably this is part of a safety circuit?

    The contactor also energises the brake to release it. This is normally how it's done.

    It would not work to connect the brake to U1/W1 when using an inverter, only if DOL. The brake must be released before the inverter starts. This can be really tricky if there is a load affected by gravity.

    If the inverter is tripping, you will normally get a fault code that you can look up to see the exact cause, have you done this? It may also be a mechanical problem and the inverter is doing its job by tripping.

    Really hard to know without seeing the full picture.

    Edit, it is also normal for a 200V 1~ input inverter to wire the motor in delta.


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