Motors temperature

Temperature detectors embedded in the motor winding give close, accurate indication of motor temperature. Both conventional resistance temperature detec tors (RTD) and special thermistors (highly temperature-sensitive nonlinear resistors) are used. With appropriate auxiliaries these devices can indicate or record motor temperature, alarm, and/or shut down the motor. 

As the windings are heated rapidly, the test voltage must be applied as quickly as possible. Care should be taken to ensure that the motor temperature does not... 

Such relays are in the form of a small tube inside which is a loosely fitted rotatable shaft, held by a very thin film of this alloy. The alloy senses the motor temperature through a heater connected in series with the motor terminals and surrounding this tube. When the motor current exceeds the predetermined value, the alloy melts and enables the shaft to rotate and actuate the lever of the tripping mechanism. 

INDUSTRY RULE OE THUMB - EACH 10°C REDUCTIDN IN MOTOR TEMPERATURE DOUBLES THE EXPECTED LIFE OF MOTOR WINDINGS... 

Table 14-1 IB is useful in comparing motor temperature rise versus class of insulation. See section NEMA MG-1, Rev. 1, Part 1, Section 1, p. 15, Classification of Insulation Systems. ...

Maximum air temperature (advise whether sun shines on motor). See reference 60 for comments on motor temperature rise. 

Speed adjuslmeiU from base speed downward is obtained by armature voltage control. The armalure current and torque in this range is limited by the thyristor ratings or motor temperature rise. Control above base speed at constant horsepower is obtained by field weakening. An example system is shown in Figure. 3-17a. In this... 

All reactions were carried out in 700-mL stainless steel, high pressure reaction vessels. The reaction solution was added, along with a Teflon-coated stirring bar, to a vessel that was flushed and loaded with CO to the desired pressure. The vessel was heated in an insulated oven, which rests on a magnetic stirring motor. Temperature control ( 1°C after the desired reaction temperature was reached) was maintained using a proportional temperature controller with a thermocouple inserted in a thermowell,. which extended below the solution level of the reaction vessel as a sensor. Heating the reaction vessel from room temperature to 160°C typically required from 40 to 45 minutes. 

If the airflow reading is doubtful, then check the temperature and SO2 % of exit gases from the furnace, operation of downstream units, and production rate of the plant. Check setting on metering pumps, current drawn by blower motor, temperatures of furnace and downstream converter passes, and rate of dilution water added, and correlate to material balance once a day/two days to estimate the loss of unreacted SO2 from stack. 

The diameter of pipeline to the driving motor 3 is optimized as d3=32mm when the difference of the water supply volume between the motor 1 and motor 3 reaches the minimum. The flow rate of cooling pipehne and the motor temperature can be adjusted by varying the diameter of the pipe. The larger the pipeline diameter, the flow volume distributed to cooling... 

A high motor temperature can indicate obstruction of cooling air flow or, if accompanied by high amperage, an increase in the gas load. Hig h bearing temperatures can indicate misalignment or improper lubrication. 

Also, the motor trips are activated, not by excessive motor temperatures, but by an excessive measured amp load to the motor. This is called the FLA (full limit amp load) point. The FLA point may be increased by perhaps 10%, but this will reduce the motor s operational life. Our motor trips at home are activated not by the measured amp load, but by excessive motor temperatures. 

Speed control by way of adjusting power frequency is becoming more and more important for economical throughput or presstme capacity variation of modern process machinery. Several key parameters that must be considered when applying induction motors to adjustable frequency controllers include the load torque requirements, current requirements of the motor and the controller ciurent rating, the effect of the controller wave-shape on the motor temperature rise, and the required speed range for the application. 

The motor load inertia capability for a controller/motor is much higher, since the controller can limit the motor current to 100 percent or less. This would result, however, in longer acceleration times than starting the motor across the line. Harmonics cause additional motor temperature rise over the temperature rise that occurs for sine-wave power operation. As a rule of thumb, for every 10 C rise in temperature, the motor insulation life is cut in half. This explains why it is important to consider the additional temperature rises associated with adjustable-frequency control power and to follow the suggested rating curves provided by capable motor manufacturers. 

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