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BK Control Transformer

Home >  Products >  Transformers >  EI Transformers >  BK Control Transformer

Industrial Control Transformer for Machine Tools and Automation Equipment

Custom input voltage, output voltage, VA rating, terminals and mounting options designed around your equipment’s continuous and inrush loads.

  • Overview
  • Recommended Products

Custom Control Transformer for Industrial Machine Tools

Application-matched AC control power for contactors, relays, PLC auxiliary circuits, solenoids, electromagnetic brakes and industrial control cabinets.

ECKO BK control transformer are designed to convert the main AC supply into a stable control voltage for industrial equipment.

We customize the input voltage, output voltage, VA rating, frequency, insulation system, terminal arrangement, mounting bracket and protection components according to your equipment requirements.

Key Product Features:

  • Designed for continuous load and momentary inrush VA
  • Single or multiple input voltage taps
  • Single, center-tapped or multiple output windings
  • 50 Hz, 60 Hz or 50/60 Hz designs
  • Custom terminal blocks, lead wires and connectors
  • Copper winding available
  • Class B, Class F or Class H insulation options
  • Custom mounting dimensions and hole spacing
  • Optional fuse, thermal protector and electrostatic shield
  • Routine electrical and safety inspection before shipment

Control Transformer Specifications

Parameter Standard and Custom Options
Product Name Control Transformer
Reference Input 220 VAC or Customized
Reference Output 12 VAC / 4.17 A
Typical Custom Power Range 25 VA–5 kVA
Input Voltage Options 110 V, 120 V, 220 V, 230 V, 240 V, 380 V, 400 V, 415 V, 440 V or 480 VAC
Output Voltage Options 6 V, 12 V, 24 V, 36 V, 48 V, 110 V, 220 VAC or customized
Frequency 50 Hz, 60 Hz or 50/60 Hz
Phase Single phase
Core Type EI laminated silicon-steel core
Winding Material Copper winding available according to the approved specification
Insulation Class Class B, Class F or Class H
Output Configuration Single output, center-tapped output or multiple isolated outputs
Terminal Options Terminal block, screw terminal, Faston tab, lead wire or custom connector
Mounting Method Foot mounting, chassis mounting or customized bracket
Protection Options Fuse, thermal protector, electrostatic shield and grounding terminal
Application Control panels, machine tools, automation equipment, HVAC systems and motor-control circuits
Compliance Support CE, CQC, RoHS support, subject to the exact model and construction
Testing Electrical function and safety testing according to the approved inspection plan

Note: The specifications above describe the reference product and common customization capabilities. Final voltage, power, dimensions, temperature rise, protection, test conditions and compliance requirements will be confirmed in the approved technical drawing.

Built for the Real Demands of Industrial Control Circuits

1. Designed for Coil Inrush and Continuous Load

Recommended Detail Image: Close-up of the transformer coil and winding area.

Control devices such as contactors, solenoids and electromagnetic brakes can draw several times their normal current during pickup. ECKO evaluates both momentary inrush VA and continuous sealed VA to help maintain sufficient secondary voltage during switching.

2. Frequency-Correct EI Laminated Core

Recommended Detail Image: Close-up of the stacked EI silicon-steel laminations.

The EI laminated core is selected according to the rated voltage, frequency, power and temperature-rise requirement. Correct magnetic design helps control no-load current, audible noise, core loss and operating temperature.

3. Accessible and Clearly Arranged Terminals

Recommended Detail Image: Close-up of the orange finger-safe terminal blocks.

Finger-safe terminal blocks simplify control-panel wiring and future maintenance. Terminal quantity, numbering, direction, spacing and voltage markings can be customized to match the customer’s wiring diagram.

4. Application-Matched Insulation System

Recommended Detail Image: Close-up of the insulated winding, bobbin and insulation tape.

Bobbin material, insulation tape, varnish, creepage distance and clearance are selected according to the operating voltage and end-equipment requirements. Class B, Class F and Class H insulation systems are available.

5. Strong and Customizable Mounting Bracket

Recommended Detail Image: Close-up of the metal bracket and slotted mounting holes.

The metal frame supports stable chassis installation and effective heat dissipation. Overall dimensions, bracket shape, mounting-hole distance and terminal orientation can be customized for installation inside limited cabinet space.

6. Controlled Product Identification

Recommended Detail Image: Close-up of the transformer label and terminal diagram.

The approved label can display input voltage, output voltage, frequency, power rating, terminal map and customer part number. Batch codes, serial numbers and customized wiring symbols are also available for product traceability.

Customization Options

Control Transformers Customized Around Your Equipment

ECKO provides electrical, mechanical and documentation customization for OEM customers, control-panel manufacturers and industrial-equipment producers.

Input Voltage Customization

Available input voltages include:

  • 110 VAC
  • 120 VAC
  • 220 VAC
  • 230 VAC
  • 240 VAC
  • 380 VAC
  • 400 VAC
  • 415 VAC
  • 440 VAC
  • 480 VAC
  • Customer-specified input voltage

Multi-tap primary windings can be designed for equipment that will be used in different countries or under different mains-voltage conditions.

Output Voltage Customization

Common output voltages include:

  • 6 VAC
  • 12 VAC
  • 24 VAC
  • 36 VAC
  • 48 VAC
  • 110 VAC
  • 220 VAC
  • Multiple isolated outputs
  • Center-tapped outputs
  • Customer-specified voltage and current

Power and Load Customization

The transformer can be designed according to:

  • Continuous load VA
  • Contactor or relay inrush VA
  • Sealed coil VA
  • Number of connected control devices
  • Simultaneous switching sequence
  • Intermittent or continuous duty
  • Minimum acceptable pickup voltage
  • Allowable full-load voltage drop

Insulation and Protection Options

Available options include:

  • Class B insulation
  • Class F insulation
  • Class H insulation
  • Primary fuse
  • Secondary fuse
  • One-shot thermal protector
  • Resettable thermal protector
  • Electrostatic shield
  • Grounding terminal
  • Enhanced insulation between primary and secondary windings

Terminal and Connection Options

We can customize:

  • Finger-safe terminal blocks
  • Screw terminals
  • Lead wires
  • Faston terminals
  • Customer-specified connectors
  • Terminal numbering
  • Wiring diagrams
  • Terminal direction and spacing

Mechanical Customization

Mechanical options include:

  • Overall transformer dimensions
  • Maximum installation height
  • Mounting-bracket design
  • Mounting-hole spacing
  • Slotted or round mounting holes
  • Core size
  • Terminal orientation
  • Label position
  • Installation direction

Documentation Options

Depending on the project, ECKO can provide:

  • Product specification
  • Electrical wiring diagram
  • Approved sample report
  • Inspection report
  • Material declaration
  • RoHS or CE documentation
  • Compliance documentation for the specified model

Control Transformers for Industrial Switching and Auxiliary Power

A control transformer provides a dedicated AC control voltage for industrial switching devices and auxiliary circuits. It can also provide galvanic isolation between the main supply and the control circuit when separate primary and secondary windings are used.

Industrial Control Cabinets

control transformers are widely installed inside electrical control cabinets to power relays, timers, contactor coils, indicator circuits and other control components.

The input voltage can be matched to the factory mains supply, while the output can be customized to 12 V, 24 V, 48 V, 110 V or another control voltage required by the panel.

Machine Tools

Machine tools frequently use contactors, electromagnetic brakes and solenoid valves that generate a high momentary current during pickup.

A properly selected control transformer helps maintain sufficient control voltage in CNC machines, cutting machines, presses, packaging machines and other production equipment.

Industrial Automation Equipment

Automation systems use control transformers to supply auxiliary AC power for PLC interfaces, relays, actuators, sensors and control circuits.

Multiple secondary windings can be designed when different control devices require separate voltage circuits or electrical isolation.

HVAC and Refrigeration Systems

Control transformers are used in chillers, refrigeration systems, air-handling equipment and commercial HVAC systems.

They can supply control voltage to contactors, valves, relays, thermostatic circuits and other auxiliary devices. The design should consider cabinet temperature, ventilation and switching frequency.

Elevators, Escalators and Automatic Doors

Lift and access-control equipment may use control transformers to power relays, magnetic brakes, door-control circuits and other auxiliary components.

Custom mounting brackets and terminal layouts are available for installation inside compact electrical cabinets.

Pumps and Water-Treatment Equipment

Control transformers can provide control power for motor starters, level-control relays, solenoid valves and monitoring circuits in pump stations, water-treatment equipment and industrial process systems.

For outdoor or humid installations, the transformer should be installed inside a suitable protective enclosure.

Why Choose ECKO?

More Than a Transformer Supplier: Engineering Support for OEM Control Systems

1. Load Analysis Before Transformer Selection

We do not select a control transformer only according to continuous watts.

Our engineering review can include the continuous VA, inrush VA, sealed VA, switching sequence, duty cycle and minimum pickup voltage of the connected contactors, relays, solenoids or brakes.

This helps reduce the risk of an undersized transformer, excessive voltage drop or unnecessary oversizing.

2. Electrical and Mechanical Design Reviewed Together

A transformer must provide the required output performance and fit correctly inside the customer’s cabinet.

ECKO reviews voltage, current, regulation, temperature rise, insulation, terminal accessibility, mounting-hole distance and overall installation space as part of the same design process.

3. Controlled Sample-to-Production Transfer

The approved product drawing, winding information, material requirements, terminal map, label content and inspection criteria become the production reference.

This controlled transfer supports consistency between approved samples and future production orders.

4. Compliance Requirements Considered Early

Certification requirements depend on the exact transformer model, insulation materials, end equipment and target market.

ECKO reviews CE, CQC, RoHS or other documentation requirements during the quotation and design stage rather than treating them as generic factory claims.

5. Engineering Communication for Custom Projects

Customers receive a clearly defined specification and drawing for approval.

Technical changes involving voltage, winding material, terminals, mounting or protection are documented to avoid misunderstandings between purchasing, engineering and production teams.

6. Experienced Transformer Manufacturing

Ecko Electrotech has manufactured customized transformers and wound components since 2000.

Our manufacturing resources include three workshops covering approximately 5,000 square metres, supported by experienced production and quality-control personnel. Our products are supplied to customers in more than 30 countries and regions.

Quality Testing

Electrical Safety and Performance Verification

ECKO combines incoming-material inspection, in-process control, routine electrical testing and design-validation testing.

The exact test items, limits, sampling level and test conditions are confirmed according to the approved product specification.

Test Item What It Verifies Control Level
Visual Inspection Workmanship, core assembly, terminals, label and surface condition Routine Inspection
Dimension Inspection Overall size, mounting-hole spacing and terminal position Routine Inspection
Winding Continuity Correct and complete electrical connections Routine Test
Turns Ratio and Polarity Correct voltage ratio and terminal relationship Routine Test
No-Load Output Voltage Secondary voltage before the load is connected Routine Test
No-Load Current Magnetic condition and core performance Routine Test
Insulation Resistance Insulation integrity between windings and accessible metal parts Routine Test
Dielectric Withstand/Hi-Pot Insulation withstand at the specified test voltage Routine Test
Rated-Load Output Voltage Voltage performance at the specified continuous load Design Validation
Voltage Regulation Difference between no-load and rated-load output voltage Design Validation
Inrush/Pickup Simulation Secondary voltage during the defined switching load As Required
Temperature-Rise Test Thermal performance under the agreed load and ambient conditions Design Validation
Noise and Vibration Check Core clamping, impregnation and mechanical assembly As Specified
Final Label Check Correct model, ratings, terminal markings and batch information Routine Inspection

Quality-Control Process:

  1. Incoming core, wire, bobbin and insulation inspection
  2. Winding-process inspection
  3. Lead-wire and terminal verification
  4. Core assembly and mechanical inspection
  5. Electrical performance testing
  6. Insulation-resistance testing
  7. Dielectric-withstand testing
  8. Final dimensions, label and packaging inspection

Important Note:

Temperature rise and output regulation depend on the transformer design, load power factor, installation orientation, cabinet temperature and ventilation. Please provide the expected operating environment so the correct validation conditions can be established.

Customization Process

From Technical Requirements to Controlled Production

Step 1: Requirement Collection

The customer provides:

  • Input voltage
  • Frequency
  • Output voltage and current
  • Continuous VA
  • Inrush VA and sealed VA
  • Load type
  • Switching sequence
  • Duty cycle
  • Ambient temperature
  • Maximum dimensions
  • Mounting-hole distance
  • Terminal requirements
  • Applicable standards
  • Estimated annual quantity

Step 2: Engineering Evaluation

ECKO evaluates the magnetic core, winding structure, conductor size, voltage regulation, temperature rise, insulation system, terminal arrangement and mounting construction.

If the inrush VA is unavailable, the customer can provide the contactor, relay, brake or solenoid datasheet for review.

Step 3: Quotation and Technical Proposal

We provide a commercial quotation together with the proposed electrical and mechanical configuration.

Any special requirements involving copper winding, thermal protection, shielding or compliance documentation should be confirmed at this stage.

Step 4: Drawing Approval

The customer reviews and approves:

  • Electrical ratings
  • Overall dimensions
  • Mounting-hole spacing
  • Terminal numbering
  • Wiring diagram
  • Label information
  • Material requirements
  • Test requirements

Sample production begins after the technical drawing and specification have been approved.

Step 5: Sample Production and Testing

Samples are manufactured according to the approved technical documents.

Electrical function, insulation, dimensions and specified validation items are checked before shipment.

Step 6: Customer Equipment Verification

The customer installs the sample in the intended equipment and verifies:

  • Mechanical fit
  • Terminal accessibility
  • Output voltage
  • Contactor or solenoid pickup
  • Operating temperature
  • Noise and vibration
  • Overall equipment performance

Step 7: Mass Production

After sample approval, the confirmed drawing, bill of materials, production process and inspection criteria are transferred to mass production.

Routine inspection and final packaging are completed according to the approved order requirements.

Frequently Asked Questions About Control Transformers

1. Does a BK control transformer provide galvanic isolation?

A conventional BK transformer with separate primary and secondary windings provides galvanic isolation between the input and output circuits.

An autotransformer does not provide the same isolation. If an autotransformer is acceptable, this must be stated clearly during the design stage.

2. Can copper winding be specified?

Yes. Copper winding can be specified as a mandatory project requirement.

The conductor material can be recorded in the approved bill of materials, technical drawing and inspection documents so it cannot be changed without customer authorization.

3. What insulation classes are available?

Class B, Class F and Class H insulation systems are available.

The suitable insulation class depends on the cabinet ambient temperature, transformer temperature rise, ventilation, duty cycle and end-equipment requirements.

A higher insulation class does not automatically mean that a higher operating temperature is desirable. The temperature-rise target should be separately defined.

4. How is temperature rise evaluated?

Temperature rise is measured under defined input voltage, frequency, load, ambient temperature and installation conditions.

The final temperature inside the customer’s cabinet can also be affected by ventilation, nearby heat sources, mounting orientation and enclosure size. Please provide the expected internal cabinet temperature during design.

5. Can you install a fuse or thermal protector?

Yes. Optional protection includes:

  • Primary fuse
  • Secondary fuse
  • Resettable thermal protector
  • One-shot thermal protector
  • Electrostatic shield
  • Grounding terminal

The final protection arrangement should also consider the upstream fuse or circuit breaker in the customer’s equipment.

6. How should the primary fuse or circuit breaker be selected?

The protection device must consider the rated primary current, energization inrush, conductor protection and applicable standard.

A fuse or breaker selected too close to the normal operating current may trip during transformer energization. An oversized device may not provide adequate protection.

The panel designer should coordinate the transformer protection with the complete electrical system.

7. Is an open-frame BK transformer short-circuit proof?

It should not be assumed that a standard open-frame BK transformer is inherently short-circuit proof.

The required fuse, circuit breaker, thermal protector and fault withstand must be defined according to the application and relevant end-equipment standard.

8. Should one side of the secondary winding be grounded?

This depends on the end-equipment standard and the customer’s control-circuit design.

ECKO supplies the required winding configuration, but grounding, overcurrent protection and conductor identification must be determined by the panel or equipment designer.

9. How can transformer noise be reduced?

Audible hum can be reduced through appropriate flux-density design, accurate core stacking, secure mechanical clamping and controlled varnish impregnation.

During installation, the transformer should be securely mounted. Thin resonant metal panels and loose mounting hardware may amplify normal magnetic vibration.

10. Can you match our existing transformer dimensions and mounting holes?

Please send:

  • Clear photos of the existing transformer
  • Product label
  • Overall dimensions
  • Mounting-hole spacing
  • Terminal positions
  • Wiring diagram
  • Input and output ratings
  • Load information

A physical sample or original drawing can further reduce the risk of mechanical or electrical incompatibility.

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