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Phase Converter Breaker Sizing Guide
Motor Load Breaker Guide • Phase Converter Help
Breaker Panel & Motor Load Breaker Guide for Phase Converter Installs
Find common single-phase breaker part numbers by panel brand, understand motor-load breaker sizing, and get practical guidance for rotary phase converters, CNC machines, air compressors, dust collectors, pumps, saws, lathes, mills, and other industrial equipment.
Single Phase to Three PhaseRotary phase converter solutions for industrial shops.
Motor Load FocusedBreaker guidance for motors, CNC, pumps, compressors, and shop equipment.
Built for ElectriciansTables, part numbers, and installation notes in one place.
Free Sizing HelpCall Phoenix Phase Converters before guessing. Guessing is how breakers become entertainment.
Start Here
Choosing the Right Breaker for a Motor or Phase Converter
A breaker for a motor circuit is not sized like a light switch or regular receptacle circuit. Motors pull high startup current. A rotary phase converter may also require a properly sized input breaker, wire, disconnect, and overload protection based on the actual equipment nameplate and local electrical code.
- ✓Match the breaker to the panel brand and type. Use only breakers listed on the panel label.
- ✓Use 2-pole breakers for 240V single-phase loads. Most phase converter input circuits use 240V single phase.
- ✓Use proper overload protection. The breaker protects the circuit from short circuits and ground faults; overloads protect the motor.
- ✓Confirm with the electrician. Wire size, distance, ambient conditions, and local AHJ requirements matter.
Phase Converter Sizing Rules
Use these as starting points for selecting the converter size before final electrical design.
Standard motor loads: size rotary phase converter at approximately 2× motor HP.
Air compressors: size at approximately 2.5× motor HP because startup load is heavier.
Fans and dust collectors: size at approximately 3× motor HP because they are heavy starting loads.
Breaker Panel Cross Reference
Common Single-Phase Breaker Panel Families
These are common breaker families used in residential and light commercial panels. Always verify the exact panel label before installation.
Siemens / ITE
Common family: QP
Examples: Q120, Q220, Q240
Square D Homeline
Common family: HOM
Examples: HOM120, HOM220, HOM240
Square D QO
Common family: QO
Examples: QO120, QO220, QO240
Eaton BR
Common family: BR
Examples: BR120, BR220, BR240
Eaton CH / CHF
Common family: CH or CHF
Examples: CH120, CH220, CH240
GE / ABB
Common family: THQL
Examples: THQL1120, THQL2120, THQL2140
1-Pole Breakers
Common 120V Single-Pole Breaker Part Numbers
For 120V single-phase motor loads. Many larger motor and phase converter circuits are 240V and use 2-pole breakers instead.
| Amps | Siemens QP | Square D HOM | Square D QO | Eaton BR | Eaton CH | GE / ABB THQL | Leviton LB |
|---|---|---|---|---|---|---|---|
| 15A | Q115 | HOM115 | QO115 | BR115 | CH115 | THQL1115 | LB115-T |
| 20A | Q120 | HOM120 | QO120 | BR120 | CH120 | THQL1120 | LB120-T |
| 25A | Q125 | HOM125 | QO125 | BR125 | CH125 | THQL1125 | LB125-T |
| 30A | Q130 | HOM130 | QO130 | BR130 | CH130 | THQL1130 | LB130-T |
| 40A | Q140 | HOM140 | QO140 | BR140 | CH140 | THQL1140 | LB140-T |
| 50A | Q150 | HOM150 | QO150 | BR150 | CH150 | THQL1150 | LB150-T |
| 60A | Q160 | HOM160 | QO160 | BR160 | CH160 | THQL1160 | LB160-T |
2-Pole Breakers
Common 240V 2-Pole Breaker Part Numbers for Single-Phase Motor Loads
Use this table for common 240V single-phase motor loads and many rotary phase converter input circuits. The final breaker must match the panel and equipment requirements.
| Amps | Siemens QP | Square D HOM | Square D QO | Eaton BR | Eaton CH | GE / ABB THQL | Leviton LB |
|---|---|---|---|---|---|---|---|
| 15A | Q215 | HOM215 | QO215 | BR215 | CH215 | THQL2115 | LB215-T |
| 20A | Q220 | HOM220 | QO220 | BR220 | CH220 | THQL2120 | LB220-T |
| 25A | Q225 | HOM225 | QO225 | BR225 | CH225 | THQL2125 | LB225-T |
| 30A | Q230 | HOM230 | QO230 | BR230 | CH230 | THQL2130 | LB230-T |
| 40A | Q240 | HOM240 | QO240 | BR240 | CH240 | THQL2140 | LB240-T |
| 50A | Q250 | HOM250 | QO250 | BR250 | CH250 | THQL2150 | LB250-T |
| 60A | Q260 | HOM260 | QO260 | BR260 | CH260 | THQL2160 | LB260-T |
| 70A | Q270 | HOM270 | QO270 | BR270 | CH270 | THQL2170 | LB270-T |
| 80A | Q280 | HOM280 | QO280 | BR280 | CH280 | THQL2180 | LB280-T |
| 90A | Q290 | HOM290 | QO290 | BR290 | CH290 | THQL2190 | LB290-T |
| 100A | Q2100 | HOM2100 | QO2100 | BR2100 | CH2100 | THQL21100 | LB2100-T |
Motor Load Examples
Phase Converter Load Examples
These examples help customers understand why the machine type matters before asking for a quote.
| Equipment Type | Example Motor | Recommended Converter Rule | Example Converter Class | Notes |
|---|---|---|---|---|
| CNC mill, lathe, mill, drill, grinder | 15 HP | 2× HP | 30 HP class | Good fit for many general industrial loads. |
| Air compressor | 20 HP | 2.5× HP | 50 HP class | Compressors pull high starting current. |
| Dust collector or fan | 25 HP | 3× HP | 75 HP class | Fans and dust collectors are heavy-starting loads. |
| 480V machine from 240V single phase | Varies | Converter + transformer | Matched package | A rotary phase converter alone does not step voltage from 240V to 480V. |
Need the right phase converter and breaker setup?
Send us your machine HP, voltage, equipment type, and what runs at the same time. Phoenix Phase Converters will help size the rotary phase converter, transformer package, and electrical requirements.
FAQ
Phase Converter Breaker FAQ
What size breaker do I need for a rotary phase converter?
The breaker depends on the converter size, input voltage, wire size, disconnect, and local code. Use the equipment nameplate and installation manual, then have the electrician verify the breaker and conductor size.
Can I use any breaker that fits my panel?
No. Use only breakers listed for the exact breaker panel. Breakers from different brands may physically fit but may not be listed or safe for that panel.
Is the breaker the same as motor overload protection?
No. The breaker is usually short-circuit and ground-fault protection. The motor still needs proper overload protection through a starter, overload relay, VFD, or listed motor protection device.
Do I need a 1-pole or 2-pole breaker for a phase converter?
Most 230/240V single-phase phase converter inputs use a 2-pole breaker. A 1-pole breaker is typically for 120V loads.
Can a rotary phase converter make 480V three-phase from 240V single phase?
Yes, but it usually requires a rotary phase converter plus a step-up transformer. The phase converter creates three-phase power; the transformer changes voltage.
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