Because the turbine pace lags constantly driving the impeller (pump) speed, the pace ratio is fewer than one. Therefore there is friction within the transmission fluid which results in power losses. Slippage consumes electrical power over the coupling period. Locking the converter shell for the turbine shaft prevents this slippage https://torqueconverterclutch19741.tkzblog.com/33776317/torque-converter-clutch-options