Answer
A - IEC (International Electro-Technical Commission) & NEMA (National Electrical Man nufacturer’s Association)
IEC – Prepares & Publishes international Standards for all electrical, electronic and related technology collectively known as “electrotechnology” –
- Covers a vast range of technologies from power generation, transmission, distribution, home
appliances, solar batteries, marine energy etc.
- IEC closely follows the ISO & the ITU
- IEC standards that are not jointly developed with ISO have numbers in the range 60,000- 79,999. E.g.
ISO/IEC 63000.
- IEC has 89 member countries. India is also the member.
- Headquarters are in Geneva, Switzerland.
NEMA – is the largest trade association of electrical equipment manufacturers in USA. It is known for developing industry standards that ensure safety, reliability & compatibility of electrical products such as enclosures, motors, plugs
- It defines a set of protect types for electrical enclosures based on their ability to guard eqpmnt from
envrnmntal hazards like dust, water, oil & corrosion.
- Sets standards for North America.
- NEMA participates extensively in the IEC at both Technical and management levels.
IEC v/s NEMA
- IEC equipment is usually less expensive but NEMA can withstand overloads better.
- IEC takes up significantly less space but NEMA takes more space, less precision in design.
- IEC equipment are more delicate but NEMA equipment is more rugged, better withstand abuse.
- NEMA starters are serviceable but IEC starters have to be replaced.
- Difference in Electrical motors
• IEC standards expressed in metric units while NEMA frame standards are expressed in imperial units.
• IEC motors are made of Cast Aluminium & Cast iron frames, While NEMA are made up of
rolled steel or Cast iron frames. Location of conduit box
• NEMA motors are made with conduit boxMounted on the side of motor frame (F1 or F2
Position) , while IEC motors are made with the conduit boxMounted on top of motor frame (F3 position).
• Duty Cycles are different. NEMA: Continuous, Intermittent or Special IEC uses 8 duty cycle
designations - S1 to S8.
Duty Cycle of a motor – The ratio of time a circuit is “on” to the time that circuit is “off”
- Starter Choices
• If max current is not well known, NEMA devices are often the best choice.
• Replacement of Parts NEMA. When downtime is Critical & this may be an added benefit.
• IEC devices are basically disposable below 100 amps.
• OEMs prefer IEC.
• For ordering IEC starters , you should have knowledge of load, duty cycle
• NEMA are more robust. The springs, contacts & other components can take abuse, vibration,
shock.
• NEMA: open design, so safety covers are often purchased separately or added in the order.
• IEC have more options to network components together. For Automation, IEC is the choice.