US 10,164,555 B1Granted

Virtual mid-bus generation in a power system for industrial control

AssigneeRockwel Automation Technologies Inc.

InventorPatrick E. Ozimek

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Abstract

A half-bridge inverter comprised of upper and lower switches can be placed in linear motor track sections to alternately connect a common point of all drive coils to a full-bus DC power rail (“full-bus”) and a DC reference, according to PWM command signals, functioning as a “virtual mid-bus” to allow bi-directional flow of a sum of currents of all drive coils in the section. Separate upper and lower drive switches of the half-bridge inverters that are also connected to drive the drive coils can then be controlled, according to separate PWM command signals, to synchronize their PWM cycles and duty cycle commands with respect to the virtual mid-bus at times when a mover is not present, resulting in zero voltage across the drive coils, or command different duty cycles with respect to the virtual mid-bus when a mover is present, resulting in a desired voltage across the drive coils. The desired voltage can produce a current in the drive coils to electromagnetically propel the mover.

Claims20

Dependent claims

A power system for industrial control, comprising:

a DC power supply configured to provide:
a first voltage rail providing a full bus DC voltage;
and
a DC reference;
a plurality of drive coils, wherein first sides of the plurality of drive coils are coupled to a second voltage rail;
a plurality of upper switches arranged between the first voltage rail and second sides of the plurality of drive coils, each upper switch being configured to selectively connect a second side of a drive coil to the first voltage rail;
a plurality of lower switches arranged between the DC reference and the second sides of the plurality of drive coils, each lower switch being configured to selectively connect the second side of a drive coil to the DC reference;
an upper mid-bus generation switch arranged between the first voltage rail and the second voltage rail, the upper mid-bus generation switch being configured to selectively connect the second voltage rail to the first voltage rail;
and
a lower mid-bus generation switch arranged between the DC reference and the second voltage rail, the lower mid-bus generation switch being configured to selectively connect the second voltage rail to the DC reference,
wherein the upper and lower mid-bus generation switches receive first Pulse Width Modulated (PWM) command signals according to a first duty cycle commanding the switches to provide the first voltage rail or the DC reference to the first side of the plurality of drive coils to produce a virtual mid-bus, and
wherein upper and lower switches of the pluralities of upper and lower switches corresponding to a drive coil receive second PWM command signals according to a second duty cycle commanding the switches to provide the first voltage rail or the DC reference to the second side of the drive coil.

9 more elements

A method for electromagnetically propelling a mover in a linear motor drive system, the method comprising:

providing a first voltage rail and a DC reference from a DC power supply to a track segment, the first voltage rail providing a full bus DC voltage, the track segment defining a path along which a mover travels, the track segment receiving power from the DC power supply for electromagnetically propelling a mover, the track segment including:
a plurality of drive coils spaced along the track segment, wherein first sides of the plurality of drive coils are coupled to a second voltage rail;
a plurality of upper switches arranged between the first voltage rail and second sides of the plurality of drive coils, each upper switch being configured to selectively connect a second side of a drive coil to the first voltage rail;
a plurality of lower switches arranged between the DC reference and the second sides of the plurality of drive coils, each lower switch being configured to selectively connect the second side of a drive coil to the DC reference;
an upper mid-bus generation switch arranged between the first voltage rail and the second voltage rail, the upper mid-bus generation switch being configured to selectively connect the second voltage rail to the first voltage rail;
and
a lower mid-bus generation switch arranged between the DC reference and the second voltage rail, the lower mid-bus generation switch being configured to selectively connect the second voltage rail to the DC reference;
receiving first Pulse Width Modulated (PWM) command signals according to a first duty cycle commanding the upper and lower mid-bus generation switches to provide the first voltage rail or the DC reference to the first sides of the plurality of drive coils to produce a virtual mid-bus, and
receiving second PWM command signals according to a second duty cycle commanding the upper and lower switches of the pluralities of upper and lower switches corresponding to a drive coil to provide the first voltage rail or the DC reference to the second side of the drive coil for electromagnetically propelling a mover when the track sensor detects a mover is proximal to the drive coil.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/896,260Filed 14 Feb 2018
Granted: 25 Dec 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

H02P 7/025
The DC motors being of the linear type: the DC motors being of the moving coil type, e.g. voice coil motors
H02J 1/02
Circuit arrangements for DC mains or DC distribution networks: arrangements for reducing harmonics or ripples
H02K 41/031
Synchronous motors; Motors moving step by step; Reluctance motors: of the permanent magnet type
H02M 7/5395
With automatic control of output wave form or frequency: by pulse-width modulation