The Miller CP-300 and CP-200 were both gas-metal arc electric welders (GMAW or MIG) manufactured by Miller Electric Manufacturing Company, introduced in 1994. As of April 2011, both of these welders are discontinued, but they are still available on the used market. The main difference between the two units was that the CP-300 was usable with a wider range of input voltage. It was also the more powerful of the two otherwise similar models.
The shipping weight of the CP-300 was 297 pounds. and its net weight was 287 pounds. The CP-200 was lighter, at 261 lbs. shipping weight and 251 pounds net weight.
Differences in Voltage
The CP-300 ran on three-phase electrical power of 200, 220, 230, 380, 415, 460 or 520 volts AC, at either 50 or 60 Hz. The CP-200 ran on three-phase electrical power of 200, 230 or 460 volts AC at 60 Hz. Maximum open-circuit voltage was rated at 14-44 volts DC for the CP-300, as opposed to 13-39 volts DC for the CP-200.
Differences in Input Amperage
Input amperage at rated output for the CP-300 were 38A at 200 volts (V), 34.5 A at 220V, 33A at 230V, 20A at 380V, 18.3 A at 415V, 16.5 A at 460V and 14.6 A at 520V. For the CP-200 the amperage was 21.4 A at 200V, 18.6 A at 230V and 9.3 A at 460V.
Input amperage for the CP-300 when idling was 3.0 A at 200V, 2.8 A at 220V, 2.7 A at 230V, 1.9 A at 380V, 1.7 A at 460V and 1.1 A at 520V. For the CP-200 the idling amperage was 2.2 A at 200V, 2.0 A at 230V and 1.0 A at 460V.
Differences in Welding Power
The rated output for the CP-300 was 300 amperes, 32 volts DC at 100 per cent duty cycle and 390 amperes, 32 volts DC at 60 per cent duty cycle. The rated output for the CP-200 was 200 amperes, 28 volts DC at 100 per cent duty cycle and 260 amperes, 28 volts DC at 60 per cent duty cycle. (100 per cent duty cycle refers to 10 minutes of continuous welding, whereas 60 per cent duty cycle refers to six minutes of welding followed by four minutes resting.
Differences in Energy Usage
The CP-300 used 12.3 kilowatts of energy for welding and .68 kilowatts when idling. The CP-200 used 7.0 kilowatts of electricity for welding and .53 kilowatts when idling. Expressed in kilovolt-amperes (kVA), the figures are 13.1 and .97 versus 7.4 and .76 for the CP-300 and the CP-200 active and idling, respectively.