Page 318 - Electronic Mechanic - TP - Volume - 2

ELECTRONICS MECHANIC - CITS

7 Insulation Class: The highest temperature in the motor’s hottest spot has a serious impact on the life of the
electric motor. The temperature that occurs at that spot is a combination of motor design temperature and the
ambient temperature. The insulation class shows the motor’s ability to withstand temperatures over time.
The motors have different insulation capabilities. The insulation cades show their thermal tolerance of ability
to survive at a specified temperature for a period of time. The higher the designated code letter the greater the
heat capability.
It is based on the highest temperature the material can withstand continuously without degrading of reducing
motor life. IES specify 5 different types of insulation classes:
• Class A – 105c
• Class B – 130c
• Class E – 120c
• Class F – 155c
• Class H – 180c
8 Temperature Rise: Each class of insulation has a maximum motor winding temperature rise and a maximum
temperature rating. In addition, a hot spot temperature rise is specified which pertains to motor windings that
are surrounded by other windings.
9 Frequency: This shows the input electricity frequency that the motor is designed to operate at.
Usually for motors the input frequency is 50 to 60 Hz. If more than one frequency is marked on the nameplate
then other parameters that will differ at different input frequencies have to be indicated on the nameplate as
well.
10 Motor Rated Power: KW is an expression of the motor’s mechanical output rating its ability to deliver the
torque needed for the load at rated speed.
11 Full Load Speed: Full-load speed is the speed at which rated full-load torque is delivered at rated power
output this speed is sometimes called slip-speed or actual rotor speed.
12 Rated Operating Current: this corresponds to the rated power output together with voltage and frequency.
The current may deviate from the nameplate amperes if the phases are unbalanced of if the voltage turns out
to be lower than indicated.
13 Power Factor: Power factor is indicated on the nameplate as either “PF” or cos ᵠ. Power factor is an expression
of the ratio of active power to apparent power expressed as a percentage.
14 Ambient Temperature: The maximum ambient temperature lists the temperature at which the motor can
operate and still be within the tolerance of the insulation class at the maximum temperature rise.
15 Altitude: This indication shows the maximum height above sea level at which the motor will remain within its
design temperature rise, meeting all other nameplate data.
16 Motor Weight: This shows the weight of the motor 78kg
17 Serial Number: This shows the serial number of the motor. As it is unique to the motor knowing this number
can help when liaising with manufacturers or M&E companies about the type of motor you have.

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CITS : E & H - Electronics Mechanic - Exercise 214