Vacon 100 Applications Manual

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Vacon 100 Applications Manual Manual pdf 69 page image

Vacon HVAC Application vacon • 6624-hour support +358 (0)201 212 575 • Email: vacon@vacon.com33.6.11 Group 3.9: ProtectionsParameters of Motor thermal protection (P3.9.6 to P3.9.10)The motor thermal protection is to protect the motor from overheating. The drive is capable ofsupplying higher than nominal current to the motor. If the load requires this high current thereis a risk that the motor will be thermally overloaded. This is the case especially at lowfrequencies. At low frequencies the cooling effect of the motor is reduced as well as itscapacity. If the motor is equipped with an external fan the load reduction at low speeds is small.The motor thermal protection is based on a calculated model and it uses the output current ofthe drive to determine the load on the motor.The motor thermal protection can be adjusted with parameters. The thermal current ITspecifies the load current above which the motor is overloaded. This current limit is a functionof the output frequency.The thermal stage of the motor can be monitored on the control keypad display. SeeChapter 3.5.Parameters of Stall protection (P3.9.11 to P3.9.14)The motor stall protection protects the motor from short time overload situations such as onecaused by a stalled shaft. The reaction time of the stall protection can be set shorter than thatof motor thermal protection. The stall state is defined with two parameters, P3.9.12 (Stallcurrent) and P3.9.14 (Stall frequency limit). If the current is higher than the set limit and theoutput frequency is lower than the set limit the stall state is true. There is actually no realindication of the shaft rotation. Stall protection is a type of overcurrent protection.Parameters of Underload protection (P3.9.15 to P3.9.18)The purpose of the motor underload protection is to ensure that there is load on the motorwhen the drive is running. If the motor loses its load there might be a problem in the process,e.g. a broken belt or a dry pump.Motor underload protection can be adjusted by setting the underload curve with parametersP3.9.16 (Underload protection: Field weakening area load) and P3.9.17 (Underload protection:Zero frequency load), see below. The underload curve is a squared curve set between the zerofrequency and the field weakening point. The protection is not active below 5Hz (the underloadtime counter is stopped).If you use long motor cables (max. 100 m) together with small drives (≤ 1.5 kW) themotor current measured by the drive can be much higher than the actual motorcurrent due to capacitive currents in the motor cable. Consider this when setting upthe motor thermal protection functions.The calculated model does not protect the motor if the airflow to the motor isreduced by blocked air intake grill. If the control board is powered off, the model isinitialised based on the value which had been calculated before the power off(memory functionality).If you use long motor cables (max. 100 m) together with small drives (≤ 1.5 kW) themotor current measured by the drive can be much higher than the actual motorcurrent due to capacitive currents in the motor cable. Consider this when setting upthe motor thermal protection functions.13006.emf13006.emf13006.emf