Motors continuous duty

The drive motor is a brushless dc torque motor, rated for continuous duty. Motor winding insulation is a high grade material which is capable of a service life of 40 years in the reactor helium atmosphere. The stator windings are vacuum impregnated. 

ManuEictuFen of motors classify them accoidii to the amount of time the motor needs to be operated. The motors are generally classified as continuous duty or intermittent duty. The continuous du motors are used in applications where the motor is ejqpected to operate over a period of an hour or longer. In some applications, continuous operation of the motor may be requited. In applications where the motor is expected to operate fi>r short periods of time and then rest, the intermittent duty motors are fiiund. The continuous duty motors are mote expensive than the intermittent duty motors. 

As far as the difficulties with the thermal overload motor switch are concerned, it has to be remembered that these mechanisms are generally based on a bimetallic foil, although different types exist (e.g. the more expensive quick trip type). The thermal behaviour of the motor is different from that of the bimetallic device and, in particular, a switch regulated for continuous duty motors does not behave as well for discontinuous duty motors as those used for valves. For this reason, the curve interruption time-current of the latter must be lower than that of the former (about 80 per cent). As already mentioned, however, it is difficult to satisfy the two specifications generally imposed by the plant operator ... 

AR331 1.40 Qualification tests of continuous-duty motors installed inside the containment of water-cooled... 

This output coixesponds to a continuous duty of drive. It must be suitably corrected for the duty cycle the motor has to perform (see equation (3,11)), i.e. 

Duty cycles Continuous duty (CMR) (S ) Periodic duties Factor of inertia (FI) Pleating and cooling characteristic curves Drawing the thermal curves Rating of short motors Equivalent output of short time duties Shock loading and use of a flywheel... 

The chemical and petrochemical industries specify continuous duty service. This means that the motor can operate indefinitely when handling the specified horsepower (rated) load at the proper voltage. To specify less than continuous duty is uneconomical and not good design practice. 

Use of wound-rotor induction motors has been largely in continuous-duty constant-speed supplications where particularly high starting torques and low starting currents are required simultaneously, such as in reciprocating pumps and compressors. These motors are also used where only alternating current is available to drive machines that require speed adjustment, such as types of fans and conveyors. 

Adjustable-speed shunt-wound motors with field control are designed for operation over speed ranges of 3 to 1 or greater. Standard adjustable-speed motors are rated in three ways tapered horsepower, continuous, 40°C rise constant horsepower, continuous, 40°C rise and constant horsepower, 1 hr,. 50°C rise, of the next larger horsepower rating than for continuous duty. 

In common with other power system equipment, motors need to be derated to suit a high ambient temperature. Equipment that is manufactured in America, UK and Europe is usually based on a maximum design temperature of 40°C. For higher ambient temperatures, e.g. 50°C as found in the Middle East and Ear East, the continuous duty output power and supply current would need to be reduced. The continuous duty is that as defined as type SI in IEC60034 part 1. International standards recommend performance and design criteria suitable for 40°C. Although most of these standard requirements will apply to ambient temperatures above 40°C there may be some addition restrictions to apply. In particular aspects of full-load current, duty, radiation of heat loss and outer surface temperature will need to be considered, see for example IEC60034 part 1 clauses 11 and... 

Overload protection is recommended for all motors, especially coolant pump motors, and shall be provided for each motor rated at more than 0.5 kW. Continuously operating motors over 1 kW shall be protected against overloads and against a stalled rotor state with built-in thermal sensors typically employed (EN 60034-11). The use of appropriate protection devices for special-duty motors (e.g., rapid traverse, locking, rapid reversal) is recommended. For motors with ratings less than or equal to 2 kW, overload protection may not be required. 

PLC Digital Outputs—-Use 24 V for indicator lights and alarms. AC is first preference, DC is second preference. For pneumatic or hydraulic solenoids and motor starters, 115 V AC modules can be used. Solenoids should be rated for continuous duty. 

Power pumps typically have high efficiency and are capable of developing very high pressures. Either electric motors or turbines can drive them. They are relatively expensive pumps and can rarely be justified on the basis of efficiency over centrifugal pumps. However, they are firequently justified over steam reciprocating pumps where continuous duty service is needed due to the high steam requirements of direct acting steam pumps. 

Duty. All motors used for mixer applications should be rated for continuous duty, since even batch runs may take more than the anticipated time should problems develop. 

If a short-time duty is performed on a Continuous Maximum Rating (CMR) motor with some no-load or idle running, the temperature rise 0 may not reach its maximum value, 0 , us shown in curve (c) of Figure... 

In motors for periodic duty, the test should be continued until thermal equilibrium has been reached. Unless otherwise agreed, the duration of one cycle should be 10 minutes for the purpose of this test. Temperature measurements should be made at the end of a cycle to establish thermal equilibrium. 

The movement is processive, kinesin motors typically taking 100 steps before dissociating from the microtubule.201 2123 Kinesin is bound to the microtubule continuously. Its duty ratio is nearly 1.0 (the same is true for the bacterial flagellar motor ... 

High-pressure specification canned-motor centrifugal pumps can provide the solution for the hardest pumping duties. The pump illustrated in Figures 8 and 8.1 has to pump a corrosive suspension in a continuous flow at a starting temperature of 250°C and an inlet pressure of... 

Care should be taken when specifying the duty of multi-speed motors to ensure that the windings are appropriately rated for continuous or short-term duty since this may affect the amount of heat and temperature rise produced in the windings and also the effectiveness of any shaft-mounted cooling fans that may be employed. 

A switchboard consists of 20 circuit breakers. Each circuit breaker has, two indicator lamps each taking 1 amp continuously, a tripping solenoid taking 5 amps for one second, and a spring charging motor for reclosing which takes 3 amps for 30 seconds. The battery needs to supply current for 4 hours when a mains failure occurs. The ampere-hour (AH) duty is -... 

Typical RMS duty cycles for drum hoists assume a continuous process with infinite time constant. Drive equipment time constants are not normally taken into account in the Duty Cycle calculation commonly used in the industry, which almost universally sets the hoist motor RMS and peak power requirements. 

Motor carrier officials and drivers have been, and will continue to be, prosecuted for egregious examples of record of duty status falsification. 

Shaded-Pole Motors. Instead of a start winding, shaded-pole motors have a continuous solid-copper loop around a small portion of each salient pole (Fig. 5.107). This shading coil causes the reaction necessary to start the motor, but produces rather low starting and accelerating torque. Because of their low starting torque, shaded-pole motors are best suited to hght-duty apphcations such as direct-drive fans and blowers. Efficiency and power factor are also lower than that of other single-phase motors. 

There are various methods of starting a decanter wnth an inherently high inertial load. A variable speed drive might be considered, if changes in machine speed are deemed to be important due to varying process conditions. However, a large majority of decanter applications use a fixed speed main drive motor. Once at speed, a decanter s motor has one of the simplest duties. It is never subjected to cyclic overloads, never subjected l i continuous vibration and never subjected to severe braking, electrically or mechanically. It is seldom stopped and restarted. 

A practical sodium borohydride system is shown in Figure 8.25. The solution is pumped over the reactor, releasing hydrogen. The motor driving the pump is turned on and off by a simple controller that senses the pressure of the hydrogen, and which turns it on when more is required. The solution is forced through the reactor, and so fresh solution is continually brought in contact with the catalyst. The rate of production is simply controlled by the duty cycle of the pump. The reaction takes place at room temperature, and the... 

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