Ohmite 250 Series Thin Stackohm Vitreous Enamel Power Resistors Instructions
- June 13, 2024
- Ohmite
Table of Contents
Ohmite 250 Series Thin Stackohm Vitreous Enamel Power Resistors
Instructions
When limited space is a consideration, choose Ohmite’s “thin” stack able 250
Type resistors. These oval-shaped ceramic-core resistors feature a low profile
to permit installation in spaces with minimal height. They are also equipped
with integral mounting brackets so they can be fastened to a chassis and
stacked in locations with limited surface area.
When properly fastened, the mounting brackets add a heat sinking benefit
resulting in a smaller size per watt.
Durable 250 Type resistors are fully welded and coated with lead free vitreous
enamel.
FEATURES
- Small size-to-power ratio.
- Stackable
- Integral mounting bracket conducts heat to mounting surface.
- Low profile for use in equipment where space is limited.
- All-welded construction.
- RoHS compliant product available Jan. 2006 Add “E” suffix to part number to specify
SPECIFICATIONS
Material
Coating: Lead free vitreous enamel.
Core: Ceramic.
Terminals: Tinned lug with hole.
Derating: Linearly from 100% @ +25°C to 0% @ +350°C.
Electrical
Tolerance: ±5% (J)
Power rating: Based on mounting a single resistor on a metal surface
measuring 10” (254mm) square by .04” (1.016mm) thick. Reduce rating by 15%
when mounting on non-metallic surface.
Overload: 5 times rated wattage for 5 seconds.
Temperature coefficient:
1 to 20Ω: ±400 ppm/°C.
Over 20Ω: ±260 ppm/°C
Dielectric withstanding voltage:
500 VAC: 10 and 20 watt rating.
1000 VAC: 30, 40 and 55 watt rating (measured from lug to mounting
bracket)
To calculate max. amps: use the formula √P/R
Note: When resistors are stacked, use washers or spacers as required to insure clearance and improve power dissipation.
*Reference dimension only; varies according to resistance value
Dimensions (in. /mm)
Series| Wattage| Ohms| Length L| Length A|
Voltage
---|---|---|---|---|---
F10| 10| 1.0-15K| 0.750 / 19.050| 1.000 / 25.400| 187
F20| 20| 1.0-50K| 2.000 / 50.800| 2.313 / 58.750| 815
F30| 30| 1.0-10K| 1.250 / 31.750| 2.000 / 50.800| 281
F40| 40| 1.0-25K| 2.000 / 50.800| 2.750 / 69.850| 655
F55| 55| 1.0-30K| 3.500 / 88.900| 4.250 / 107.950| 1405
Adjustable versions available. Consult factory.
Other sizes available. Consult factory.
Also available in low cost Centohm coating. Consult Factory
STOCK PART NUMBERS FOR STANDARD RESISTANCE VALUES
Ohmite Mfg. Co. 1600 Golf Rd., Suite 850, Rolling Meadows, IL 60008 • Tel. 1-866-9-OHMITE • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com 31
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