Power Drive Circuit
10 - 7
Fwd/Rev Loading
Error Amplifier
U5D
Error Amplifier U5D controls the plunger velocity and pressure limit
when forward or reverse loading. Below are descriptions of velocity
and pressure limit control.
Velocity Control:
U5D controls motor velocity by increasing or decreasing the error sig-
nal, based upon comparisons of the Load Profile (U4C), and inverted
Velocity signal (U2B and U5A). U4C produces a load profile voltage
that indicates the desired speed of the motor, while Velocity Amplifier
U2C produces an output voltage that represents the actual speed of
the motor. The Velocity signal is inverted by U5A, and summed with
the Load Profile at the inverting input to U5D.
If there is a negative difference (actual plunger rate is below the
desired plunger rate), U5D will increase the error signal, firing the
SCR bridge earlier in the sine-wave, producing more power for the
motor. Likewise, if there is a positive difference (actual plunger rate is
above the desired plunger rate), U5D will decrease the error signal,
firing the SCR bridge later in the sine-wave, producing less power for
the motor.
Pressure Limit Control:
If the output of U1B indicates pressure in excess of 200 PSI, Q15 and
Q17 conduct, summing a positive voltage with the negative load pro
-
file voltage (from U4C) to reduce the input to U5D. The lower input
reduces the error signal from U5B, thus limiting load rate and pres
-
sure.
To Next Page
Loading...
