Variable frequency electrostatic drive
AssigneeWisconsin Alumni Research Foundation
InventorsAditya N. Ghule, Baoyun Ge, Daniel Colin Ludois
Life of this patent
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Abstract
A variable speed drive for an electrostatic motor provides feedback control by conversion of measured current phases provided to the motor into a vector in a rotating rotor framework. This vector is used for evaluating corrective voltages and then reconverted to a non-rotating framework for application to the motor electrodes. Current-source drive circuits provide current stabilized outputs making such sophisticated control tractable.
Claims20
A variable speed drive for an electrostatic motor of a type having a stator with multiple stator electrodes adapted to generate a rotating stator electric field vector about an axis and a rotor having multiple rotor electrodes providing a rotor electric field interacting with the rotating electric field primarily by electrostatic forces rather than magnetic forces, the variable speed drive comprising:
- a set of current-source drives adapted to connect to the multiple stator electrodes wherein the current-source drives provide a set of electrical switches in series with a current source implemented by an inductance serving to regulate current to the stator electrodes;
- a rotor position determination system;
- an ABC-dq transformation circuit receiving a position signal from the rotor position detector and measures of outputs of the current-source drives to develop a measured d-q vector;
- an input for receiving the desired d-q vector;
- a comparison circuit providing an error vector based on the measured d-q vector and desired d-q vector;
- and
- a dq-ABC transformation circuit receiving the position signal and providing an output based on the error vector to develop a set of electrode signals provided to the current-source drives for driving the stator electrodes of the electrostatic motor.
A variable speed drive for an electrostatic motor of a type having a stator with multiple stator electrodes adapted to generate a rotating stator electric field vector about an axis and a rotor having multiple rotor electrode providing a rotor electric field interacting with the rotating electric field primarily by electrostatic forces rather than magnetic forces, the variable speed drive comprising:
- a set of current-source drives adapted to connect to the multiple stator electrodes;
- a rotor position determination system;
- an ABC-dq transformation circuit receiving a position signal from the rotor position detector and measures of outputs of the current-source drives to develop a measured d-q vector;
- an input for receiving the desired d-vector;
- a comparison circuit providing an error vector based on the measured d-q vector and desired d-q vector;
- and
- a dq-ABC transformation circuit receiving the position signal and providing an output based on the error vector to develop a set of electrode signals provided to the current-source drives for driving the stator electrodes;
- wherein the input circuit selects an angle for the desired d-q vector between the d- and q-motor axes according to a formula:
- γ
- ma
-
-
- x
- =
- -
- a
-
-
- sin
-
- (
- C
- 1
-
- mf
-
- V
- fd
- ±
- C
- 1
-
- mf
- 2
-
- V
- fd
- 2
- +
- 8
-
- C
- 2
-
-
- s
- 2
-
- V
- s
- 2
- 4
-
- C
- 2
-
- s
-
- V
- s
- )
- ±
- 5
-
- %
- .
- where:
- γmax is an optimum angle magnitude between the desired d-q voltage vector and the q-axis;
- C1mf is a magnitude of a fundamental of a coupling capacitance between any one of the stator terminals to any one of the rotor terminals;
- C2s is a magnitude of a second harmonic of a coupling capacitance between any two stator terminals;
- Vfd is a magnitude of the dc rotor voltage;
- and
- Vs is the magnitude of the fundamental of the stator voltage.
A method of providing variable speed control of an electrostatic motor of a type having a stator with multiple stator electrodes adapted to generate a rotating stator electric field vector about an axis and a rotor having multiple rotor electrodes providing a rotor electric field interacting with the rotating electric field primarily by electrostatic forces rather than magnetic forces, comprising the steps of:
- providing a set of current-source drives for providing current to the stator electrodes wherein the current-source drives provide a set of electrical switches in series with a current source implemented by an inductance serving to regulate current to the stator electrodes;
- receiving a position signal from the rotor position detector and measures of outputs of the current-source drives to develop a measured d-q vector;
- receiving a desired d-q vector and comparing it to the measured d-q vector to produce an error vector;
- and
- transforming the error vector to produce a set of outputs provided to the current-source drives for driving the stator electrodes of the electrostatic motor.
Dependencies are inferred from the claim text.