Commutating energy suppression circuit for an electronically commutated DC motor

DETAILED DESCRIPTION According to the present invention, a voltage surge sensing and control circuit is coupled to the dc power supply inputs of the electronic commutator.
This circuit acts to sense the input voltage which is to be applied across the ECDC motor windings.
When an input surge voltage is determined to be high enough to impose a voltage approaching the voltage rating of any power transistor which is off at the time of the surge, the voltage surge control acts to turn all the transistors on.
The voltage across the transistor thus becomes the on voltage or conduction voltage of the transistor, thereby protecting the power transistors from an excess voltage which would result in catastrophic avalanche of the transistor.
The voltage surge is thus imposed across the winding and isolated from the power transistors.
The energy in the surge is primarily dissipated in the stator winding of the motor.
The present invention also seeks, as a second feature, to minimize commutation energy imposed on the transistors by using inherent commutation energy suppression.
This is accomplished by using a bifilar wound stator, bonded bifilar wire, and phase decoupling capacitors.
The bonded bifilar wiring acts to minimize the field inductance field, whereas the phase decoupling capacitors act to absorb energy generated after the winding phases are deenergized.
The ECDC motor includes a stator with a plurality of windings, a permanently magnetized rotor cooperating with the stator, a plurality of switching transistors, each of which is connected to conduct current to one of the windings in response to a control signal, a switching control means responsive to the position of the rotor for outputting said control signals, the dc power input means for supplying power potential necessary to conduct current across the windings, and the over-voltage sensing and control circuit, including means responsive to over-voltage from the dc power input means for providing an output effective to cause conduction of each of the plurality of switching transistors simultaneously