A welding type power supply comprising: - an outer housing; - a wind tunnel (501, 503, 505, 507, 509, 511), disposed within the outer housing, having an air flow direction, and a first cross direction perpendicular to the air flow direction; - a fan; and - electrical components disposed to receive power and provide a welding type output, wherein the electrical components include a first group of components that require air flow for cooling, and a second group of components; wherein the first group of components are disposed at least partially in the wind tunnel (501, 503, 505, 507, 509, 511) and the second of components are not disposed in the wind tunnel, characterized in that a first width of the wind tunnel (501, 503, 505, 507, 509, 511) in the first cross direction at a first location in the air flow direction is less than a second width of the wind tunnel in the first cross direction at a second location in the air flow direction, wherein the first group of components includes components that are attached to heat sinks (516, 517) disposed in a first portion of the wind tunnel (501, 503, 505, 507, 509, 511) having the first width in the first cross direction, and the first group of components further includes magnetic components disposed in a second portion of the wind tunnel having the second width in the first cross direction, wherein the wind tunnel (501, 503, 505, 507, 509, 511) includes a transition portion (503, 509) where the width of the wind tunnel in the first cross direction changes in the transition portion, and the transition portion (503, 509) is located between the first location and the second location, in the air flow direction, wherein the fan is disposed at a first end of the wind tunnel (501, 503, 505, 507, 509, 511) closer to the first location than the second location. - an outer housing; - a wind tunnel (501, 503, 505, 507, 509, 511), disposed within the outer housing, having an air flow direction, and a first cross direction perpendicular to the air flow direction; - a fan; and - electrical components disposed to receive power and provide a welding type output, wherein the electrical components include a first group of components that require air flow for cooling, and a second group of components; wherein the first group of components are disposed at least partially in the wind tunnel (501, 503, 505, 507, 509, 511) and the second of components are not disposed in the wind tunnel, characterized in that a first width of the wind tunnel (501, 503, 505, 507, 509, 511) in the first cross direction at a first location in the air flow direction is less than a second width of the wind tunnel in the first cross direction at a second location in the air flow direction, wherein the first group of components includes components that are attached to heat sinks (516, 517) disposed in a first portion of the wind tunnel (501, 503, 505, 507, 509, 511) having the first width in the first cross direction, and the first group of components further includes magnetic components disposed in a second portion of the wind tunnel having the second width in the first cross direction, wherein the wind tunnel (501, 503, 505, 507, 509, 511) includes a transition portion (503, 509) where the width of the wind tunnel in the first cross direction changes in the transition portion, and the transition portion (503, 509) is located between the first location and the second location, in the air flow direction, wherein the fan is disposed at a first end of the wind tunnel (501, 503, 505, 507, 509, 511) closer to the first location than the second location.