Below is some useful information for electricians regarding motor nameplates and contactor duty cycles etc etc... Please do not take this as gospel and do correct me if I am wrong. If you are unsure of any of this information it is best to do your own research.

Motor duty cycle
Note this information is not for NEMA (American) motors, rather it is for IEC motors as used by the rest of the planet. Motors usually state on the nameplate the duty cycle the motor is to be used for. Anything other than continuous rating or higher requires a rest period to cool. The IEC duty cycle ratings are as follows:
S1 - Continuous duty. The motor works at constant load for enough time to reach temperature equilibrium.
S2 - Short-time-duty. The motor works at constant load, but not long enough to reach temperature equilibrium, and rest periods are long enough for the motor to reach ambient temperature.
S3 - Intermittent periodic duty. Sequential, identical run and rest cycle with constant load. Temperature equilibrium is never reached. Starting current has little effect on temperature rise.
S4 - Intermittent periodic duty with starting. Sequential, identical start, run and rest cycles with constant load. Temperature equilibrium is never reached, but starting current affects temperature rise.
S5 - Intermittent periodic duty with electric braking. Sequential, identical cycles of starting, running at constant load, electric braking, and rest. Temperature equilibrium is not reached.
S6 - Continuous operation with intermittent load. Sequential, identical cycles of running with constant load and running with no load. No rest period.
S7 - Continuous operation with electric braking. Sequential, identical cycles of starting, running at constant load, and electric braking. No rest period.
S8 - Continuous operation with periodic changes in load and speed. Sequential, identical duty cycles of start, run at constant load and given speed, then run at other constant loads and speeds. No rest.

Contactor utilisation rating
Below are some utilisation ratings as you will find on IEC contactors, again I think the americans have there own system. The ratings are as follows:
AC1 - Non-inductive or slightly inductive loads (essentially resistive PF>.95). These are primarily non-inductive or slightly inductive loads. Basically no overload currents and a resistive load.
AC2 - Starting of slip-ring motors, starting and switching off.
AC3 - Starting of squirrel-cage motors and switching off only after the motor is up to speed. (Make LRA, Break FLA). Basically a typical motor contactor designed to handle inrush when starting and FLA when breaking.
AC4 - Starting of squirrel-cage motors with inching and plugging/reversing duty. Rapid Start/Stop. (Make and Break LRA)
AC-5a - Switching of electric discharge lamps.
AC-5b - Switching of incandescent lamps.
AC-6a - Switching of transformers.
AC-6b - Switching of capacitor banks.
AC-7a - Slightly inductive loads in household appliances and similar applications.
AC-7b - Motor-loads for household applications.
AC-8a - Hermetic refrigerant compressor-motor control w/ manual resetting of overload releases.
AC-8b - Hermetic refrigerant compressor-motor control w/ automatic resetting of overload releases.
AC11 - Auxiliary (control) circuits.
Note, FLA - full load amps, LRA = locked rotor ampacity
DC-1 - This applies to all DC loads where the time constant (L/R) is less than or equal to one msec. These are primarily non-inductive or slightly inductive loads.
DC-3 - This applies to starting and breaking of a shunt motor during inching or plugging. The time constant shall be less than or equal to 2 msec. On energization, the contactor sees current similar to that in Cat. DC-2. On de-energization, the contactor will break around 2.5 times the starting current at a voltage that may be higher than the line voltage. This would occur when the speed of the motor is low because the back e.m.f. is low. Breaking is severe.
DC-5 - This applies to the starting and breaking of a series motor during inching or plugging. The time constant being less that or equal to 7.5 msec. On energization, the contactor sees about 2.5 times the nominal full load current. On de-energization, the contactor breaks the same amount of current at a voltage which can be equal to the line voltage. Breaking is severe.
DC-6 - Switching or incandescent lamps.

IP (ingress protection) codes
There are several different uses of IP Codes, as described in IEC 529. IP Codes can have the following arrangement:
First character only, such as IP 3X, second character only, such as IP X4, or both characters, such as IP 34. The first character indicates the degree of protection against the ingress of solid foreign objects. First character definitions are as follows:
0 - Non-protected.
1 - Protected against solid foreign objects of 50 mm diameter and greater.
2 - Protected against solid foreign objects of 12.5 mm diameter and greater.
3 - Protected against solid foreign objects of 2.5 mm diameter and greater.
4 - Protected against solid foreign objects of 1.0 mm diameter and greater.
5 - Dust-protected.
6 - Dust-tight.
The second character of the IP Code indicates the degree of protection against the ingress of water with harmful effects. Second character definitions are as follows:
0 - Non-protected.
1 - Protected against vertically falling water drops.
2 - Protected against vertically falling water drops as the enclosure is tilted 15 degrees.
3 - Protected against spraying water.
4 - Protected against splashing water.
5 - Protected against water jetting.
6 - Protected against powerful water jetting.
7 - Protected against temporary immersion.
8 - Protected against continuous immersion.

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