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CAN CSA E61558-2-6-03: Safety of Power Transformers, Power Supplies, Reactors and Similar Products – Part 2-6: Particular Requirements for Safety Isolating Transformers for General Application
Canadian Adoption of IEC 61558-2-6 Setting Essential Safety and Performance Requirements for Safety Isolating Transformers Used in General Applications
Scope and Application
CAN CSA E61558-2-6-03 represents the Canadian adoption of the international standard IEC 61558-2-6, focusing on safety isolating transformers for general application. This standard applies to single-phase and poly-phase safety isolating transformers with a rated supply voltage not exceeding 1 000 V AC and a rated output not exceeding 10 kVA (single-phase) or 16 kVA (poly-phase). The output voltage of a safety isolating transformer is limited to 50 V AC rms or 120 V ripple-free DC, ensuring protection against electric shock in applications such as power tools, medical equipment, toys, and low-voltage lighting systems.
The standard defines a safety isolating transformer as a transformer in which the input and output windings are separated by at least double insulation or reinforced insulation, ensuring that even a single fault in the insulation does not result in hazardous voltage on the secondary side. CAN CSA E61558-2-6-03 applies to transformers intended for both indoor and outdoor use, covering dry-type and encapsulated transformers as well as those with resin-encapsulated windings.
Important: CAN CSA E61558-2-6-03 is exclusively concerned with safety isolating transformers, not with autotransformers or step-down transformers used for other purposes. When selecting a transformer for a given application, ensure the product is specifically designed and certified as a safety isolating transformer in accordance with this standard.
The scope also includes transformers integrated into appliances or equipment where the transformer is a separate component or a built-in part. Compliance with this standard is mandatory for transformers sold in Canada under the jurisdiction of provincial safety authorities such as the Electrical Safety Authority (ESA) or via certification bodies like CSA Group.
Key Technical Requirements
CAN CSA E61558-2-6-03 establishes a comprehensive set of technical requirements to ensure the safety and reliability of safety isolating transformers. The main areas covered are electrical, thermal, mechanical, and fire protection.
Electrical Requirements
- Output Voltage Limits: The secondary no-load voltage must not exceed 50 V AC rms or 120 V ripple-free DC.
- Rated Output: Single-phase units limited to 10 kVA, poly-phase units to 16 kVA.
- Dielectric Strength: The transformer must withstand a dielectric test voltage between primary and secondary windings, and between windings and core/earth. Typical test voltages are listed in the table below.
- Creepage and Clearance Distances: Minimum distances are specified based on working voltage, pollution degree, and material group.
- Short-Circuit Protection: Transformers must be inherently short-circuit proof or provided with suitable overtemperature or overcurrent protection.
| Insulation Location | Test Voltage (V rms) – 1 min | Remarks |
|---|---|---|
| Primary to secondary (reinforced insulation) | 3 000 | For rated voltages ≤ 300 V |
| Primary to secondary (double insulation) | 3 000 | Test between combined layers |
| Primary/core, secondary/core | 1 500 | Basic insulation |
| Between independent windings (turns insulation) | 1 000 | For inter-layer insulation |
Dielectric tests are conducted with a 50/60 Hz sinusoidal voltage for 1 minute at the specified levels. Production line tests can be performed at 1.2 times the prescribed values for 1 second.
Thermal Requirements
The standard defines maximum temperature rises for windings, core, and external surfaces under rated load and overload conditions. For Class B insulation, the allowable temperature rise is 80 K (by resistance method) for windings, while for Class F insulation it is 105 K. The ambient temperature for tests is assumed to be 25 °C, with corrections for higher ambient temperature applications.
Tip: When validating transformer designs, ensure that the temperature rise tests are performed at the rated input voltage and the output loaded to the rated current. The use of thermocouples on windings (inaccessible after encapsulation) may require prior embedment during manufacturing.
Mechanical and Fire Protection
- Enclosure: Transformers must be constructed so that internal faults do not cause ejection of parts or fire. Metal enclosures must be bonded to earth.
- Terminals: Screw terminals must have a minimum size; soldered connections must be mechanically secured before soldering.
- Flammability: Insulating materials used in windings and internal wiring must meet a flammability class of at least V-2 or better (according to IEC 60707 or UL 94).
- Protective Impedance: Where used, impedance values must be selected so that access to secondary remains safe even under single-fault conditions.
Implementation Highlights
The adoption of CAN CSA E61558-2-6-03 ensures harmonization with international practices while catering to specific Canadian regulatory requirements. Key implementation highlights include:
- Marking and Instructions: Each transformer must be permanently marked with the manufacturer’s name or trademark, model number, rated input voltage, frequency, and output voltage/current. The symbol IEC 60417-5036 (double square) shall be used to indicate safety isolating transformer class. Instructions for installation and use must be provided in both English and French.
- Environmental Conditions: Transformers are classified for use in pollution degree 1 or 2 environments; for higher pollution degrees, additional enclosures or coatings are required.
- Production Testing: Routine tests include dielectric strength, earth bonding resistance (if applicable), and no-load output voltage verification. Manufacturers are required to maintain records of these tests.
- Type Tests: Designs must undergo type tests covering all clauses of the standard, particularly dielectric, temperature rise, short-circuit, and endurance tests (1000 cycles of rated operation).
Good Practice: To expedite CSA certification, submit a detailed test plan along with the sample transformers to CSA Group. Include calculations for creepage and clearance distances, demonstration of insulation system, and thermal simulation results.
Compliance and Certification Notes
CAN CSA E61558-2-6-03 is a harmonized standard referenced by the Canadian Electrical Code (CE Code) Part I. Compliance is verified by recognized certification organizations such as CSA Group, UL (C-UL), and Intertek (ETL). Key compliance considerations:
- Adoption Status: The standard carries the CSA mark, indicating full alignment with IEC 61558-2-6 (Ed. 1.0 or Amendment 1:2003). Manufacturers should verify the exact edition year when sourcing components.
- National Deviations: Canada may impose stricter requirements on certain aspects; for example, supply voltage tolerances and frequency (60 Hz) are mandatory. The standard also requires transformers used in Canada to tolerate a +6% / -10% voltage variation.
- Certification Process: A typical evaluation covers documentation review, sample testing, factory inspection, and follow-up audits. The standard does not require recertification annually but any design change must be reported to the certifier.
- Relationship with Other Standards: For transformers intended for medical or IT applications, additional standards such as CAN CSA C22.2 No. 601 series or IEC 60601-1 apply. However, CAN CSA E61558-2-6-03 can be used as a baseline safety standard.
Critical: Failure to comply with the dielectric strength and creepage requirements is the most common non-compliance finding. Ensure that the creepage distance between primary and secondary winding (reinforced insulation) is at least 8 mm for a working voltage of 250 V and pollution degree 2. Use a U-bar or slot construction if needed.
Finally, manufacturers should be aware that the standard has been superseded by newer editions (e.g., CAN CSA E61558-2-6:2010). However, CAN CSA E61558-2-6-03 remains acceptable under the CE Code as long as it is still listed by the province. It is advisable to transition to the latest edition at the earliest opportunity to benefit from updated test methods and clearer requirements.
Q: What is the difference between CAN CSA E61558-2-6-03 and IEC 61558-2-6?
A: CAN CSA E61558-2-6-03 is the Canadian adoption of IEC 61558-2-6:2003 with national modifications to reflect Canadian electrical practices, such as voltage tolerances (+6%/-10%), 60 Hz frequency, and bilingual marking requirements. The technical content is otherwise identical to the IEC document.
A: CAN CSA E61558-2-6-03 is the Canadian adoption of IEC 61558-2-6:2003 with national modifications to reflect Canadian electrical practices, such as voltage tolerances (+6%/-10%), 60 Hz frequency, and bilingual marking requirements. The technical content is otherwise identical to the IEC document.
Q: Can a safety isolating transformer certified to CAN CSA E61558-2-6-03 be used in medical applications?
A: Not directly. Medical electrical equipment requires compliance with CAN CSA C22.2 No. 60601-1 or similar. The safety isolating transformer for medical use must also meet the leakage current and isolation requirements specific to the medical standard. However, the basic insulation construction from CAN CSA E61558-2-6-03 often serves as a good starting point.
A: Not directly. Medical electrical equipment requires compliance with CAN CSA C22.2 No. 60601-1 or similar. The safety isolating transformer for medical use must also meet the leakage current and isolation requirements specific to the medical standard. However, the basic insulation construction from CAN CSA E61558-2-6-03 often serves as a good starting point.
Q: Are there any mandatory marking requirements under this standard?
A: Yes. The transformer must be marked with the safety isolating transformer symbol (IEC 60417-5036), the manufacturer’s name or trademark, model number, rated input voltage (V), frequency (Hz), output voltage (V) and current (A) or power (VA). Markings must be durable and legible. Labels in Canada must also include bilingual safety information where applicable.
A: Yes. The transformer must be marked with the safety isolating transformer symbol (IEC 60417-5036), the manufacturer’s name or trademark, model number, rated input voltage (V), frequency (Hz), output voltage (V) and current (A) or power (VA). Markings must be durable and legible. Labels in Canada must also include bilingual safety information where applicable.
Q: What is the maximum ambient temperature for testing under this standard?
A: The standard assumes an ambient temperature of 25 °C for most tests. For transformers intended for use in higher ambient environments (e.g., up to 50 °C), the manufacturer must declare the maximum ambient temperature, and all thermal tests are adjusted accordingly. Temperature rise limits remain as per the insulation class.
A: The standard assumes an ambient temperature of 25 °C for most tests. For transformers intended for use in higher ambient environments (e.g., up to 50 °C), the manufacturer must declare the maximum ambient temperature, and all thermal tests are adjusted accordingly. Temperature rise limits remain as per the insulation class.