Coil insertion machines insert prefabricated groups of coils into the stators of electric motors. Brushed DC motors are constructed with wound rotors and either wound or permanent-magnet stators. This particular design employs dual rotors and stators to sound each pitch. A Boeing 757 brake, for example, has 3 stators and 4 rotors. Nearly all universal motors are series-wound because their stators have relatively few turns, minimizing inductance. Each stage was a pair of rotors; there were no stators. Stacking factors are typically 0.95 or higher for transformer cores and machine stators. The stators are connected to the remaining terminals of the transformer. Poor grounding of motor stators can lead to shaft-to-ground bearing currents. The $50 million project included replacing the turbines, stators, wicket gates and transformers. Variable geometry (i.e., stators) enable high-pressure-ratio compressors to work surge-free at all throttle settings. Compressor handling is facilitated by 4 rows of variable stators. The shell was machined with grooves that held the stators. Units 1, 3 and 4 had their stators rewound in 1975 to 1976. The multiple stators increased turbulence in the converter, even when operating in the coupling phase.