What is the recommended Insulation Class and Temperature for Induction Motor ?

(1 Min Read)

• Class F insulation with Class B temperature rise is the most commonly required insulation system for industrial motors i.e., max. temperature rise of 80 °C above ambient temperature.
• The use of Class F insulation (ambient temperature 40 °C + Max. permissible temperature rise 105 °C + Hotspot temperature margin 10 °C ) with Class B (ambient temperature 40 °C + Max. permissible temperature rise 80 °C + Hotspot temperature margin 10 °C ) temperature rise gives motors a 25 °C safety margin. This can be used to increase the loading of the motor for limited periods, to operate at higher ambient temperatures or altitudes or with greater voltage and frequency tolerances. It will help to extend insulation life.
• Hence a Class F Motor's insulation can go up to to a max temperature of 40+80+10 = 130°C is the recommended limit by most of the manufacturers.

Why Single Stranded Wires are not used for Domestic Wirings ?

(2 Min Read)

• In Domestic wiring circuits, Conduits (Pipe protecting electrical wiring) have large number of bends and turns with smaller dia.
• Single stranded wire is not  flexible, hence cable won't go through easily inside the conduits and also increase the chances of metal fatigue and the wire breaking as a result. Because of this, single stranded wires are best suited for products that won’t encounter much space restrictions and bends.
• Multi-Strand wiring is more flexible and less susceptible to cracking and metal fatigue(weakness) than single stranded conductors. This makes it the preferable solution for domestic wiring.

Domestic Wiring Conduits & Junction Box

What is the Direction of Rotation of Induction Motor if we Connect R, Y, B in U, V, W ?

(1 Min Read)

    When the mains supply is R, Y, B is connected to stator terminals marked U, V, and W respectively then the motor will Rotate Clockwise, as viewed from the D-end. The direction of rotation can be reversed by interchanging any two of the three conductors connected to a starter switch or motor.

What are the IEC Standards for Induction Motors ?

(5 Min Read) 

    The following guide serve as reference lists for Electrical and Mechanical IEC Standards that apply to most Low Voltage Induction Motors. In this context, Low Voltage refers to Motors that operate at voltages less than 1000 V and produce a maximum power of 1000kW. 

    IEC 60034 is an International Standard by International Electrotechnical Commission(IEC)  for rotating electrical machinery.

    A Standard is a specifications document established as a result of consensus between international technical experts working for a standards organization such as the International Electrotechnical Commission (IEC), the European Committee for Electrotechnical Standardization (EN), or a national standards organization (NEMA in the US, DKE in Germany).

                                              

Electrical Standards:

• IEC 60034-1 - Rating and performance
• IEC 60034-2-1 - Standard methods for determining losses and efficiency from tests (excluding machines for traction vehicles)
• IEC 60034-2-2 - Specific methods for determining separate losses of large machines from tests – Supplement to IEC 60034-2-1
• IEC 60034-8 - Terminal markings and direction of rotation
• IEC 60034-11 - Thermal protection
• IEC 60034-12 - Starting performance of single-speed three-phase cage induction motors
• IEC 60034-17 - Cage induction motors when fed from converters – Application guide
• IEC 60034-25 - Guidance for the design and performance of AC motors specifically designed for converter supply
• IEC 60034-26 - Effects of unbalanced voltages on the performance of three-phase cage induction motors
• IEC 60034-30 - Efficiency classes of single-speed three-phase cage induction motors(IE-Code)
• IEC 60034-31 - Selection of energy-efficient motors including variable speed applications – Application guide
• IEC 60038 - Standard voltages
• IEC 60050-411 - International electrotechnical vocabulary – Chapter 411: Rotating machines

Mechanical Standards:

• IEC 60034-5 - Degrees of Protection provided by the integral design of rotating electrical machine (IP code)
• IEC 60034-6 - Methods of cooling (IC code)
• IEC 60034-7 - Classification of types of construction, mounting arrangements and terminal box position (IM Code)
• IEC 60034-9 - Noise limits
• IEC 60034-14 - Mechanical vibration - Measurement, evaluation and limits of vibration severity
• IEC 60072-1 - Dimensions and output series for rotating electrical machines Part 1: Frame sizes 56 to 400 and flange numbers 55 to 1080
• IEC 60529 - Degree of protection provided by enclosure (IP Code)