Representative imageControl Transformers
Control transformers (also called control-circuit or machine-tool transformers) are small single-phase isolation transformers that step a machine's line voltage down to a safe, stable control voltage — commonly 110/115 V or 24 V — to power contactors, relays, solenoids, PLCs, indicator lamps and other control-circuit devices.
Overview
Control transformers (also called control-circuit or machine-tool transformers) are small single-phase isolation transformers that step a machine's line voltage down to a safe, stable control voltage — commonly 110/115 V or 24 V — to power contactors, relays, solenoids, PLCs, indicator lamps and other control-circuit devices. Their defining feature is high inrush (VA) capability: they are designed with good voltage regulation so that the large momentary current drawn when electromagnetic coils energize (often 3-10x rated) does not collapse the secondary voltage and drop out the very devices they feed. They use robust insulation, generous thermal margin and often multiple primary taps to suit a range of supply voltages. A buyer chooses a control transformer when a control panel needs a dedicated, isolated, regulation-stable low-voltage supply rated for the inrush of its switching devices.
Specifications
| Rating | typically 25 VA to ~5 kVA (continuous) |
|---|---|
| Primary voltage | e.g. 240 / 380 / 400 / 415 / 440 / 480 / 600 V (often multi-tap) |
| Secondary voltage | commonly 110 / 115 / 120 V or 24 / 48 V |
| Phases | single-phase |
| Frequency | 50 / 60 Hz |
| Inrush (sealed-VA) capability and regulation rating | |
| Insulation/thermal class (B / F / H) and temperature rise | |
| Mounting | panel / DIN-rail / foot-mount, terminal or stud connections |
| Fingersafe terminals / fusing provisions where required | |
| Standards | IEC 61558-2-2 / IS 12021, UL/CSA where applicable |
Applications
- Machine-tool and industrial control panels
- Contactor, relay and solenoid control circuits
- PLC and automation control supplies
- Indicator/pilot lamps and operator devices
- OEM equipment control power
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