| 摘要 |
A speed control device is provided such that the speed of DC motors is controlle d to remain constant with varying voltages supplied from a power source. A given application for such a speed control device is in the use of portable, hand-held Metal Inert Gas (MIG) welders. The power requirements of a portable MIG welder are twofold. Power is required for the generation of a welding current to enable the workpiec es to be sufficiently heated and thus, welded together, and power is also required to dri ve a wire spooler which provides wire at a constant rate, leading to accurate and consiste nt welds. The speed control device provided ensures constant power delivery for both power requirements, regardless of variations in the voltage of a power supply and irre spective of a mechanical load asserted on the welder.
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