Miller Spectrum 875
Key Specifications
rated output
max open circuit voltage
input voltage
input hz
max thickness mild steel
max thickness stainless steel
How much does the Miller Spectrum 875 cost?
Estimated price range
Our best estimate for a cnc plasma cutting in this class — not a quote from Miller Electric. Configuration moves it a long way.
Overview
The Miller Spectrum 875 is a plasma cutting power source with two ratings: 50 A at 140 VDC with a 60% duty cycle, and 40 A at 140 VDC with a 100% duty cycle. Miller lists a maximum cut thickness of 7/8 in. (22.2 mm) on both mild steel and stainless steel, and 5/8 in. (15.9 mm) on aluminum.
The second rating is the one to plan long cuts around. At 40 A the unit is rated to run without a cooling pause, so a mechanized pass or a long seam does not have to be broken up. Turning it up to 50 A buys cutting capacity at the cost of rest time, since a 60% duty cycle allows six minutes of cutting in ten. The continuous rating keeps most of the peak output, which is what makes the lower setting practical for everyday work.
Input is 208 V or 220/230/240 V at 50/60 Hz. No lower input voltage appears in the table, so the unit needs that class of supply wherever it is used. Maximum open-circuit voltage is listed as 305 VDC. Travel speed is given as 15 IPM for each of the three materials, a figure that belongs to the thick end of the range; no speed is listed for thinner plate.
The case measures 18.5 in. long, 8.75 in. wide and 13.5 in. high and weighs 48 lb. That is more than twice the 21 lb. of the Spectrum 625 X-TREME, though still within what one person can lift onto a cart or bench. Air supply, torch and CNC interface are not covered by the table and should be confirmed for the package being ordered.
Full Specifications
| Parameter | Value |
|---|---|
| Rated Output | 50 A at 140 VDC, 60% Duty Cycle; 40 A at 140 VDC, 100% Duty Cycle |
| Max Open Circuit Voltage | 305 VDC |
| Input Voltage | 208 V, 220/230/240 V |
| Input Hz | 50/60 Hz |
| Max Thickness Mild Steel | 7/8 in. (22.2 mm) |
| Max Thickness Stainless Steel | 7/8 in. (22.2 mm) |
| Max Thickness Aluminum | 5/8 in. (15.9 mm) |
| Travel Speed Mild Steel | 15 IPM |
| Travel Speed Stainless Steel | 15 IPM |
| Travel Speed Aluminum | 15 IPM |
| Net Length | 18.5 in. |
| Net Width | 8.75 in. |
| Net Height | 13.5 in. |
| Machine Weight | 48 lb. |
Specifications sourced from millerwelds.com — verified 2026-10-03
Strengths & Limitations
Strengths
- Rated 40 A at 140 VDC with a 100% duty cycle, so cutting at that output needs no cooling pause
- Peak rating of 50 A at 140 VDC with a 60% duty cycle
- Maximum cut thickness of 7/8 in. (22.2 mm) on mild steel, and the same 7/8 in. (22.2 mm) on stainless steel
- Works from 208 V as well as 220/230/240 V input, at 50/60 Hz
- 48 lb. in a case 18.5 in. long, 8.75 in. wide and 13.5 in. high
Limitations
- The lowest input voltage listed is 208 V, so it cannot be planned for a lower-voltage outlet
- Aluminum capacity is 5/8 in. (15.9 mm), below the 7/8 in. (22.2 mm) listed for the two steels
- The Spectrum 625 X-TREME weighs 21 lb., less than half of this unit's 48 lb.
- Travel speed is listed only as 15 IPM, with no figure for thinner material, and the table has no rows for air supply or a CNC interface
Best For
Frequently Asked Questions
01
Miller gives two ratings. At 50 A and 140 VDC the duty cycle is 60%, which is six minutes of cutting in every ten. At 40 A and 140 VDC the duty cycle is 100%, meaning the unit is rated to cut continuously at that output.
02
The listed maximum is 7/8 in. (22.2 mm) on mild steel, 7/8 in. (22.2 mm) on stainless steel and 5/8 in. (15.9 mm) on aluminum. The travel speed row shows 15 IPM for all three materials.
03
The input voltage row lists 208 V and 220/230/240 V, at 50/60 Hz. No lower voltage is listed, so it cannot be planned for a standard low-voltage outlet. The table does not give input current, so size the circuit from Miller's documentation for the unit.
04
The Spectrum 875 weighs 48 lb. and measures 18.5 in. long, 8.75 in. wide and 13.5 in. high. The Spectrum 625 X-TREME weighs 21 lb. The 875 is the heavier unit to move but carries the 50 A rating and the 100% duty cycle at 40 A.
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