Design DC motor control using SCR

Discussion in 'The Projects Forum' started by ngocnhan, Feb 19, 2014.

  1. ngocnhan

    Thread Starter New Member

    Feb 12, 2014
    3
    0
    The following text is the prompt of the project
    "
    A thyristor is used to turn on and off a 50-A DC motor every 60 seconds. We wish to design a circuit to control the motor using a GE. C150 slow switching device.

    The manufacturer suggests that if the current in the thyristor rises too quickly, that is a high di/dt, the device can be destroyed. Therefore, some inductance must be placed with this device, so that di/dt is below the maximum limit. Also, this device may turn on (without any gate pulses), if the forward voltage is too high. That is known as dv/dt turn-on and it may lead to an improper operation of the circuit and the DC motor. A simple RC snubber may limit the dv/dt of the applied forward voltage.

    Your design should also include the thyristor protection units, a switching device/mechanism using an auxiliary electronic switches (such SCR’s, power MOSFET’s, BJT’s, etc), and a commutation circuit.

    Reporting Requirements: All components used in this project must have values with their spec. sheets attached (if any). Your references must be listed in a separate sheet. (i.e. Reference Sheet). Your plots/graphs are completely labeled and all calculations are clearly explained with the proper units. Note: Group works are encouraged but your individual works and their originalities are observed.

    Specification of GE. C150 (E, N, and P) Series:

    Repetitive Peak Forward and Reverse Voltages 500 V (C150E)
    800 V (C150N)
    1000 V (C150P)
    Reverse and Forward Leakage Current 10 - 20 mA
    Holding Current 20 mA
    RMS Current 100 A
    Forward Voltage Drop 1.2 - 2.0 V
    Peak One-Cycle Surge (60 Hz) 1500 A
    I2t for Fusing 7000 amp2.sec
    dv/dt 200 – 500 V/µsec
    di/dt 500 A/µsec
    Gate Trigger Voltage 1.5 – 3 V
    Gate Trigger Current 50 – 200 mA
    Turn On-Time 3 µsec
    Turn Off-Time 100 µsec
    "

    Beside the 50A given for the DC motor, no other info was provided.
    Ra, La , and Ea of the motor were not given. Are these values listed in the motor manufacturing spec sheet?

    If not, how can I figure out the information of the load (Motor) like (Ra, La and Ea) so i can get the firing angel ??
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    A copy of the GE SCR Manual would be helpfull. Might contact GE, USA, Electronics Park, Syracuse, N. Y. 13201 [ 1972 inf. ]
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,524
    2,369
    Is this an actual project or an assignment?
    As normally two SCR's in a bridge would be used on 1ph for DC motor control, 1 SCR would only result in half wave control?
    Max.
     
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