Design DC motor control using SCR

Thread Starter

ngocnhan

Joined Feb 12, 2014
3
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 ??
 

Bernard

Joined Aug 7, 2008
5,784
A copy of the GE SCR Manual would be helpfull. Might contact GE, USA, Electronics Park, Syracuse, N. Y. 13201 [ 1972 inf. ]
 

MaxHeadRoom

Joined Jul 18, 2013
28,686
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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