Insulation Class, Temperature Rise and Duty Cycles of High-temp Motors
Insulation Class and Temperature Rise
The classification of motor insulation class is based on the allowable limit temperature of the insulation materials used in the motor. There are several grades such as A, E, B, F, H and so on. The so-called allowable limit temperature refers to the maximum allowable operating temperature of the motor insulation material, which reflects the heat resistance of the insulation material. Insulation materials are divided into Class A, Class E, Class B, Class F, and Class H according to their heat resistance. The allowable temperatures (℃) are 105, 120, 130, 155, and 180℃. As shown below.
When the motor uses Class B insulation, the temperature rise limit of the stator winding (resistance method) should not exceed 80K; when the motor uses Class H insulation, the temperature rise limit of the stator winding should not exceed 125K. STEPPERONLINE can provide customization of up to H-class high-temperature motors.
Duty Cycles of Operating Electrical Motors
The classification of motor insulation class is based on the allowable limit temperature of the insulation materials used in the motor. There are several grades such as A, E, B, F, H and so on. The so-called allowable limit temperature refers to the maximum allowable operating temperature of the motor insulation material, which reflects the heat resistance of the insulation material. Insulation materials are divided into Class A, Class E, Class B, Class F, and Class H according to their heat resistance. The allowable temperatures (℃) are 105, 120, 130, 155, and 180℃. As shown below.
When the motor uses Class B insulation, the temperature rise limit of the stator winding (resistance method) should not exceed 80K; when the motor uses Class H insulation, the temperature rise limit of the stator winding should not exceed 125K. STEPPERONLINE can provide customization of up to H-class high-temperature motors.
Duty Cycles of Operating Electrical Motors
| Duty Cycles | Description | |
|---|---|---|
| S1 | Continuous duty | The motor works at a constant load for enough time to reach temperature equilibrium. This working system is usually suitable for long-term load situations, such as fans or conveyor belt applications. |
| S2 | Short-time duty | Run for a given time under constant load. Before reaching thermal stability, the motor is shut down for a long enough time to allow the motor to cool down (the temperature difference with the cooling medium is within 2K). In this working system, the motor running time is very short, and the heating time is much shorter than the cooling time. Motors with this working system are commonly found in cranes, household appliance drivers, valve controllers, etc. |
| S3 | Intermittent periodic duty | Operate according to a series of identical working cycles that do not reach thermal equilibrium. Each cycle includes a period of constant load operation and a period of shutdown (power-off shutdown time).The starting current of each cycle in this working system has no significant impact on the temperature rise. However, the cycle must last for 10 minutes, and the duty cycle must be one of four types: 15%, 25%, 40%, or 60%. Motors with this working system are commonly found on stamping and drilling machines. |
| S4 | Intermittent periodic duty with starting | Run according to a series of identical working cycles, each cycle includes a starting time that has a significant impact on temperature rise, a constant load running time and a power-off shutdown time. It is similar to S3, but it adds starting on the basis of S3, so it requires the moment of inertia of the motor load, that is, the acceleration capability of the motor. Motors of this working system are widely used in metal cutting machines, drilling machines, mining hoists, etc. |
| S5 | Intermittent periodic duty with electric braking | It operates according to a series of identical working cycles. Each cycle includes a starting time, a constant load running time, a fast electric braking time and a power-off stalling time. Similar to S4, the moment of inertia of the motor load is required. However, all time periods are too short to reach their respective steady-state temperatures. This working motor is commonly used in billet rolling mills, robot drives, mining hoists, etc. |
| S6 | Continuous operation with intermittent load | Run according to a series of identical working cycles, each cycle includes a period of constant load operation and a period of no-load operation, but does not stop. That is, the operating cycle = work (load + no load), similar to S3, common in pressing machines, cutting machines, etc. |
| S7 | Continuous operation with electric braking | Run according to a series of identical working cycles, each cycle includes a starting time, a constant load running time and a rapid electric braking time without stopping. That is, the starting S6 is added. Mainly used in cotton gins. |
| S8 | Continuous operation with periodic changes in load and speed | Sequential, identical duty cycles run at constant load and given speed, then run at other constant loads and speeds. No rest periods. |
| S9 | Duty with non-periodic load and speed variations | Non-periodic working system in which the load and speed vary within the allowable range. This duty cycle includes frequent overloads, the value of which can exceed full load. It is relatively complex and often stipulated based on actual conditions, such as wind power generation. |
| S10 | Duty with discrete constant loads and speeds | The working system includes no less than 4 discrete load values (or equivalent loads), which can include no-load operation and shutdown. Under each load, the thermal equilibrium state is reached (even no-load or shutdown). In a working The minimum load value in the cycle can be zero. Compared with S8, it can be considered that there are many constant load movements, which require various loads and times, but do not include acceleration and deceleration. |
Updated on: 22/12/2023
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