This implies that there's a lots of electrical power lost from the torque converter, dissipated as heat. So as to make improvements to its effectiveness, brands additional a lock-up clutch on the torque converter. The Charge of the oil pressure while in the lock-up clutch is done via two valves: https://torque-converter-clutch44197.actoblog.com/34660143/5-simple-techniques-for-torque-converter-clutch