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
    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


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


    Jul 18, 2013
    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?