MODERN traction motors operate under severe conditions. The latest adopted standard for traction motors lists them as class B.1 This provides that the peak value by resistance of the armature shall not exceed 160 degrees centigrade (C), and the peak value for the fields shall not exceed 170 C. Modern traction motors on heavy Diesel-electric locomotives often exceed these temperature limits by 20 to 30 C. The temperatures in the hottest part of the armature and the hottest part of the field will exceed these average resistance measurements. Coupled with these high temperatures are severe vibration conditions, dust, water, varying humidity, highly variable maintenance, and shock. Most traction-motor equipment operates on 3,000 volts or less on direct current, or 1,500 volts or less on alternating current. The railroads expect and get long motor life coupled with a very high degree of dependability.
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