Rotor flux control in a permanent magnet electric machine

A propulsion system for an electrified vehicle, comprising:

• a permanent magnet (PM) electric machine;
• a gear unit connected to the PM electric machine;
• a cooling system for controllably circulating a fluid through passages in a rotor of the PM electric machine, the cooling system including a variable force solenoid valve receiving a pressurized fluid and controlling circulation of the pressurized fluid through the rotor in response to a control command;
• and
• a controller providing the control command effecting a fluid flow through the rotor based upon an operating point of the PM electric machine such that the fluid flow through the rotor is reduced when the operating point of the PM electric machine is below a predetermined threshold relative to a fluid flow through the rotor when the operating point of the PM electric machine is above the predetermined threshold,
• wherein the cooling system for controllably circulating the fluid through passages in the rotor of the PM electric machine diverts fluid not circulated through the passages in the rotor of the PM electric machine through a stator of the PM electric machine such that the stator receives an increased fluid flow when the rotor receives a reduced fluid flow.