| 摘要 |
A torque estimating unit (4) derives values for tool power (P) and subtracts (46) the copper losses (S), iron losses being assumed negligible, giving the power mechanically converted. The corresponding torque (Cm), compared (5) with a setting value (7, Ccons), produces an error signal. Using this, an integrator (6) passes a revised firing angle value to the thyristor gate controller (2). Motor phase current values (IA, IB), after processing (41), yield effective currents (IAeff, etc.), from which, using known motor resistance (R) the losses are calculated (45). Fundamental current values (IA1, etc.) are also produced (41), and another unit (44) using nominal - opt., measured - supply voltages calculates motor power (P). This calculation also requires the phase angle of the fundamental currents, obtained (42,43) by comparing thyristor firing times (2) with measured voltage zeros (VRS). |
