1. rated power and rated current;
    
2. rated voltage and frequency;
    
3. power factor;
    
4. speed;
    
5. type of duty;
    
6. insulation class;
    
7. degree of protection.
    

Electric Motors > Rated Power - Rated Current

The rated power of an electric motor is the mechanical power available to the shaft; it is expressed in Watt (W), in horse power (1 Hp = 745.7 W) or in metric horse power (1 CV = 736 W): for the sake of convenience it is frequently presumed that 1 CV = 1 Hp = 750 W.
The rated current is the current absorbed by the motor, fed at rated voltage and frequency, when it supplies the rated power.
The rated power differs from the absorbed power depending on the performance of the motor. It must be remembered that the rated power, or current, characterizes a well defined point of operation of the motor: the rated operation point. The actual power, or current, absorbed by the electric motor that drives an electropump depends on the point of work of the electropump: in centrifugal pumps, for example, the higher the flow rate, the greater the absorbed power.
Due to problems of overheating, and frequently to avoid cavitation, it is of fundamental importance to use any electropump within the limits recommended by its manufacturer: only in this way can we be sure of not endangering the efficient functionality and long life of the machine.

Electric Motors > Rated Voltage and Frequency

The rated voltage is the line voltage, or voltage between two phases, on the motor terminals at rated power. Its value is considered by the designer when planning the dimensions of the
machine: for correct motor function, and therefore for that of the electropump, the mains voltage must not differ much from this value: on this subject, international regulations require that motor-driven appliances be able to supply their rated power, and therefore to function correctly, when they are fed at a voltage that may vary by ±5% (6%) of the rated value.
If in a given country the mains voltage has a wide field of variation around a rated value, it is advisable to point this out to the manufacturer who may consider the possibility of designing a motor specially to deal with these characteristics.
Other important data which must always be indicated on the machine plate are the rated frequency - generally 50 Hz or 60 Hz - and the number of phases; generally single-phase or three-phase induction motors are used. As specified above, single-phase induction motors are almost always of the type with permanently in-circuit capacitor: in this case the data plate will show the capacity of the capacitor and the maximum voltage that it can withstand.

Electric Motors > Power Factor

The power factor (p.f.) or cos f, generally not known or not considered by "non-technicians", indicates the phase difference between the vectors representing voltage, on the motor terminals, and the vectors representing the current that it absorbs. This is a very important parameter for an induction motor as, together with the performance, it indicates the quality of the motor: its value is all the higher when the designer establishes "good" dimensions without speculating too much on cost (using good quality laminations, allowing for ample dimensions of the pack and the number of leads in the winding, etc.).
It must also be remembered that, in the various countries, the electric energy distribution company requires that users have a minimum value of power factor: for values below this limit the user has to pay an excess charge for the energy consumed. The distribution company also has the power to enforce the user to alter his systems so as to bring the p.f. to a value that is not below the set limit: the lower the p.f. of a system, the higher the cost that must be incurred to bring it up to the minimum set value (or, to use the technical term, to correct the power factor of the system).

The Pump > Speed

The rotation speed is the number of revolutions performed by the pump in the time unit; this is generally indicated with the letter n and measured in rpm.
All PENTAX electropumps are fitted with a 2-pole induction motor; considering the average running of the motors and the fact that the electric energy distributed in the mains generally has a frequency of 50 or 60 Hz, this gives roughly n(50 Hz) = 2750 - 2950 rpm and n(60 Hz) = 3300 - 3550 rpm.
 

Electric Motors > Type of Duty

By duty of any electric machine is meant (the definition of) the load to which the machine is subjected, including (if applicable) the time intervals devoted to starting, electric braking, idling and pause time, their duration and sequence in time.
Without pausing to describe the various types of duty defined by the standards (continuous, limited duration, intermittent, etc.), we shall simply stress that each PENTAX electropump is driven by an induction motor, which may be single-phase or three-phase depending on the model, of enclosed and self-ventilated type, suitable for continuous duty, that is able to supply the performance declared on the data plate without interruption.

Electric Motors > Insulation Class

During operation a dielectric declines, that is it gradually loses its ability to perform the task for which it is intended. We therefore speak of the life of an insulation, by which we mean the time during which the insulation's properties are kept above set values so that it can perform the functions for which it was intended.
The life of the materials used for the insulation of electric machines depends on numerous factors of different kinds: thermal, chemical, mechanical and electrical factors. Among these the most important are thermal and electrical stress.
As regards the machines, the value of the working temperature is highly important because the length of its efficient working life depends on this. In fact, although the insulations each need a limit operating temperature that must never be exceeded, the length of their efficient working life is all the greater the lower the temperature at which they are made to operate.
On the basis of these concepts, solid insulating materials are divided into classes that are conventionally identified by a letter and distinguished by the maximum acceptable temperature during operation.
The most widespread insulation classes and their respective maximum temperatures are the following:
 

Since, at the same power, the temperature of the various parts of an electric machine depends on the ambient temperature, the international standards refer more frequently not to limit temperature but to the maximum admissible overtemperature with respect to ambient temperature. More precisely, with regard to electric machines, a conventional ambient temperature is defined and limits are fixed for the overtemperatures of the windings, on the basis of the insulation class used.
Standard IEC 335-1 / 335-2-41, referring to electric pumps for domestic and similar uses, sets an ambient temperature of 25°C (which may occasionally reach 35°C) and defines the following limits for the over temperatures of the windings:

 

Standard IEC 34-1, referring to rotating electric machines and therefore applicable to electric motors, sets a conventional ambient temperature of 40°C and defines the following limits for the overtemperatures of the windings:

 

The values in brackets refer to machines with a power of less than 600 W.

To conclude we may sum up by saying that the insulation class of a given electric motor is indicative of the maximum overtemperature, with respect to the ambient temperature, that may be reached by the windings of the motor: a high admissible overtemperature indicates the use of "quality" insulating material in machine construction, making the machine suitable for use in particularly severe installations.

PENTAX electropumps are driven by electric motors with class B or class F insulation, depending on the size of the motor.
 

Electric Motors > Degree of Protection

Like other electric machines, electric motors too - and therefore electropumps - are classified according to the closing system, that is the protection against the entry of solid and liquid bodies.
The degree of protection of the casings of rotating electric machines is defined by the Standard with the initials IP (International Protection) plus two figures which may (at the manufacturer's discretion) be followed by one or two letters. As summed up in figure 6, each position in the code has a value of its own.

 

- The first characteristic figure serves as dual indication:
a) protection of persons against access to dangerous parts, that is electrically active parts or moving mechanical parts;
b) protection of the machine against the penetration of solid foreign bodies.
In progression, the figures indicate gradually higher degrees of protection. It is also understood that a machine with, for example, degree 4 also complies with the lower degrees of protection (from 0 to 3).
- The second characteristic figure indicates protection against the harmful penetration of water.
- The purpose of the additional letter is to designate the level of inaccessibility of the machine casing to fingers or hands, or objects held by a person; this letter also denotes a strictly accident-prevention function and must be used only if the protection against access is higher than that defined with the first characteristic number.
- The purpose of the supplementary letter is to indicate particular conditions concerning the type of machine or its use.

All PENTAX electric pumps are characterized by degree of protection IP44, that is they are protected against the access, to dangerous parts, of a wire or of solid bodies with dimensions higher than or equal to 1 mm (1st number), and against splashes of water coming from any direction (2nd number).