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Braking Resistor

Discussion in 'General Electronics Discussion' started by onetothree, Feb 16, 2016.

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  1. onetothree

    onetothree

    1
    0
    Feb 15, 2016
    I am installing a cable car (Loaded weight 800Kg on a 38 deg slope). using a 1.1Kw 3 phase motor (64:1 reduction gear box ) running from single phase using a 2.2kW inverter. I have installed 2 at 1600W 400 ohm braking resistors connected to the VFD in series.
    The cable car operated fine in testing until after an uphill run at full load (800Kg) was completed, when the VFD showed a motor overload fault and the resistive loads did not turn off but continued to heat until the power was turned off to the VFD. After resetting, the cable car operated correctly but the resistive loads turned on as soon as the VFD was turned on. They now do this even if the cable car is not operated. Would this indicate a failure of the braking transistor and why would this have occurred, Would the problem be solved by using an external contactor to switch on the resistors on the downhill run only? The motor is rated to 4.5A and on the uphill run was drawing 5.3A which the supplier states is within capacity. Any help in solving the problem greatly appreciated.
     
  2. Externet

    Externet

    757
    164
    Aug 24, 2009
    IF I understand correctly without an schematic, a braking transistor health is in risk to drive that much power. If the resistors are in series to the motor???, well, they will be on. A contactor as you say sounds to be a safer implementation. Troubleshoot/test the transistor, and the motor with no load.
     
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