Split phase polyphase inverter
A split phase DC to AC polyphase inverter having M phases for driving an M-phase load includes, for each phase, N subphases for producing N PWM signals at a carrier frequency. Associated with each of the M phases is one of M averaging transformers. The N PWM signals associated with each one of the M phases is input into the associated transformer. The transformer produces a PWM signal with a frequency equal to approximately N times that of the carrier frequency of that of the N input PWM signals, and with a maximum voltage step equal to the voltage amplitude V of one of the N input PWM signals divided by N. The result is an inverter circuit which produces much lower output current ripple without increasing the total power consumed by the inverter.
1 . A polyphase inverter comprising;
a first conductor;
a second conductor;
M phases, each phase comprising N inverters, each inverter comprising two inverter inputs, an inverter output, a first node coupled to the first conductor and a second node coupled to the second conductor; and
M transformers, each transformer comprising N transformer inputs and a transformer output, each of the N inverter outputs from each phase coupled to each of the N inputs of an associated one of the M transformers.
2 . The polyphase inverter of claim 1 wherein M=3.
3 . The polyphase inverter of claim 1 wherein the each of the M transformer outputs is configured to drive an electric motor.
4 . The polyphase inverter of claim 1 , wherein N=3.
5 . The polyphase inverter of claim 4 , wherein M=3.
6 . The polyphase inverter of claim 1 , wherein each inverter comprises two insulated-gate bipolar transistors.
7 . The polyphase inverter of claim 1 , wherein each inverter comprises two metal-oxide-semiconductor field effect transistors.
8 . The polyphase inverter of claim 1 , wherein each of the M transformers comprises N cores.
9 . The polyphase inverter of claim 1 , wherein each of the M transformers comprises N toroids.
10 . The polyphase inverter of claim 1 , wherein each of the M transformers comprises a plurality of center-tapped transformers.
11 . The polyphase inverter of claim 1 , further comprising a logic circuit comprising 2×M×N outputs, each output coupled to one of the 2×M×N inverter inputs.
12 . The polyphase inverter of claim 11 wherein the logic circuit is used to provide PWM signals to the inverters.
13 . A polyphase inverter comprising:
logic circuitry;
a first conductor for coupling to a first terminal of a DC power source;
a second conductor for coupling to a second terminal of the DC power source;
M phases, each phase comprising N subphases, each subphase comprising two transistors coupled in an inverter configuration, an first node coupled to the first conductor, a second node coupled to the second conductor, two inverter inputs coupled to the logic circuitry, and an inverter output; and
M transformers, each transformer comprising N transformer inputs, the N transformer inputs of each transformer being coupled to the N inverter outputs from an associated one of the M phases, and a transformer output for coupling to a load.
14 . The polyphase inverter of claim 13 wherein M=3.
15 . The polyphase inverter of claim 14 wherein the three transformer outputs are configured to supply power to an electric motor.
16 . The polyphase inverter of claim 15 wherein the M transformer outputs are configured to supply power to an electric motor.
17 . The polyphase inverter of claim 13 wherein the transistors comprise insulated gate bipolar transistors.
18 . The polyphase inverter of claim 13 wherein the transistors comprise metal-oxide-semiconductor field effect transistors.
19 . The polyphase inverter of claim 13 wherein each transformer comprises N cores.
20 . The polyphase inverter of claim 13 wherein each transformer comprises N toroids.
21 . The polyphase inverter of claim 13 wherein each transformer comprises at least one center-tapped transformer.
22 . The polyphase inverter of claim 13 wherein each transformer output is configured to drive a phase of an electric motor comprising M phases.
23 . The polyphase inverter of claim 13 wherein each transformer multiplies a switching frequency associated with an output of the subphases by N.
25 . The polyphase inverter of claim 23 wherein each transformer divides the maximum voltage step associated with the output of the subphases by N.
26 . A system for driving an electric motor, comprising;
a polyphase inverter comprising a first conductor, a second conductor, M phases wherein each phase comprises N inverters, and wherein each inverter comprises two inverter inputs, an inverter output, a first node coupled to the first conductor and a second node coupled to the second conductor, the polyphase inverter further comprising M transformers, wherein each transformer comprises N transformer inputs and a transformer output, and wherein each of the N inverter outputs from each phase is coupled to each of the N inputs of an associated one of the M transformers; and
an electric motor comprising M phases, each phase comprising an input, the output of each transformer coupled to the input of each phase of the electric motor.
27 . The system of claim 26 wherein the electric motor comprises a DC brushless electric motor.
28 . The system of claim 27 wherein the motor is coreless.
29 . The system of claim 28 wherein the electric motor comprises three phases.
30 . The system of claim 26 wherein the electric motor comprises three phases.