What is the generally allowable temperature rise in a fan motor?

With Class F insulation, the maximum allowable temperature rise ranges from 105 to 115 C for the motor’s winding insulation, depending on how the motor is configured.

What is the normal operating temperature of a motor?

The surface temperature of a continuously (and correctly) operating general purpose industrial electric motor will easily be 80 C (176 F) and perhaps as high as 100 C (212 F).

What is allowable temperature rise?

The allowable temperature rises are based upon a reference ambient temperature (40°C) and are determined by a “resistance method”, once the motor has achieved thermal equilibrium under load, the resistance of the windings is measured. The resistance of the winding is a function of temperature of the winding.

What is motor temperature rise?

Temperature rise is the change within a motor when operating at full load. For example; if a motor in a 78°F room operates continuously at full load, the winding temperature will rise. The difference between its starting temperature and its final elevated temperature is the motor’s temperature rise.

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How do you calculate motor temperature rise?

Ambient temperature is the temperature of the air (or other cooling medium) that surrounds the motor. The difference between the ambient temperature and that of a motor operating under load is the temperature rise (temperature rise = hot temperature – ambient temperature).

What happens if an electric motor gets too hot?

One of the most common performance issues in electric motors is overheating. Experts suggest that an 18°F (10°C) degree increase in motor winding temperature can directly affect the insulation of the component and reduce its lifespan by 50%.

What can cause an electric motor to overheat?

Electrical overload caused by excessive voltage supply or overwork by drawing more current will lead to overheating issues. As the motor works harder or under unusual load, heat will be the chief byproduct, leading to failure. 2. Low resistance is the most common reason behind electric motor failure.

What is 80K temperature rise?

To allow for any Hot Spots in winding lower temperature limits are specified for the insulation materials. MEZ motors have been produced with insulation class F with winding temperature rise in accordance with the class B (max 80K). This means that the motors have a temperature reserve of 25K.

What happens to insulation when temperature rises?

For insulators the conductivity of the material is increased, when the temperature is increased. When the conductivity of the material is increased, we know that the resistivity decreases and the current flow thus increases. So some insulators at room temperatures changes to conductors at high temperature.

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What are the classes of insulation?

What is meant by “Class” in insulation?

Insulation Rating Insulation Class Average Winding Temperature Rise
Class 150 or 130 B 80 degree C
Class 180 F 115 degree C
Class 200 N 130 degree C
Class 220 H 150 degree C

How hot is too hot for a motor?

The Class F (155 C) temperature rating is popular these days, so it’s a good one to discuss. With Class F insulation, the maximum allowable temperature rise ranges from 105 to 115 C for the motor’s winding insulation, depending on how the motor is configured.

What is normal bearing temperature?

Normal motor bearing operating temperatures range from 140° to 160°F. As in all bearing applications, this measurement should be taken at the bearing outer ring. If the outer ring is inaccessible, take the measurement at the housing and add 15° to 20°F to estimate the correct bearing temperature.

Is the most common cause of motor failure?

Low Resistance. The most common cause of motor failure, and arguably the most difficult to overcome, is low resistance. Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage.

Is class F insulation inverter duty?

Temperature rise is the difference between the ambient and the hot winding temperature. A motor with a 1.15 SF and class F insulation (for 1500 Hp and less) is rated at 125C per NEMA MG-1. … Motor manufacturers classify their motors as inverter duty when they use a class F insulation.

What is class B temperature rise?

For example, an 80°C rise is often referred to as a ‘Class B’ temperature rise, since 80°C is the maximum allowable temperature rise (by resistance) for a 1.0 S.F. … motor wound with Class F insulation, a Class B temperature rise at full load translates to a thermal margin of 155- (40+90) = 25°C.

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How do you check winding temperature?

The temperature of a motor winding is measured or monitored by measuring the resistance of the winding. This is done by introducing a small direct current component into the motor current, which can be done by connecting an asymmetric resistance device in the motor circuit.

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