Testing the Eurothrem 7100A Thyristor Controller

Introduction:

The Eurothrem 7100A Thyristor controller is intended to replace the Eratron SCR controller in the Prometheus laser.The Eurotherm units are speced at 100A 230/240V service with a 5 V analog control input signal.

Breadboard:

The following circuit was breadboarded to test the Eurotherms. A Stanford Research Instrument Delay Generator is use for timing the firing of the Eurothrem and the discharging of the holding capacitor.
Rep Rate 0.2Hz
Delays
A = T+0
B = T+50ms
C = T+1.2s
D = T+1.3s
AB triggers the 900ms flip/flop gating the analog signal to the Eutotherm. CD gates the discharge transistor. The control level is adjustable form 0 to 5V. The full wave bridge output voltage is ~ 160VDC.

Analysis:

The oscilloscope traces shows a built in time delay of ~ 200ms between the rising edge of the control signal input and the firing of the thyristors. If the Eurothrem units are used the 200ms delay will have to figured into the system timing.
Yellow = AB Trigger monitored at F/F input
Blue = Analog Control Signal monitored at Eurotherm input
Violet = E Charge Curve monitored on the holding capacitor
Green = Discharge Signal monitored at the Discharge input
(Written by Michael F. Klawitter)