Altivar 1260 Medium Voltage Drives Page 52 Primary components

Voltage limiting chopper (optional) 52 Altivar 1260 MV variable speed drive View of the Voltage Limiting Chopper Elements in same stack When the application returns energy to the converter, a braking chopper is installed so that there is no DC bus overvoltage. This device is capable of containing the voltage of the DC bus capacitors and maintaining it at normal operating values in the event of a momentary return of power to the DC bus. The chopper starts to function when the voltage in the bus exceeds the pre-established upper limit of operation (Chopper. Hyst.VoltHigh) and continues until the minimum voltage limit (Chopper.Hyst.VoltLow) is reached or the maximum allowable operating time (Chopper.Temp.TOnMax) is exceeded. When the chopper satisfies one of these two conditions, standby time (Chopper.Temp.TOffMin) begins. If the chopper again exceeds the upper limit of the bus during this time, the temperature of the resistor is checked and, depending on this temperature, the chopper is reactivated or not. If the chopper cannot be reactivated, an overvoltage alarm will be activated. During the time that the chopper is activated, the IGBTs are conducting electricity, allowing the energy from the bus to dissipate in the form of heat in the voltage limiting resistors. Component Characteristics Chopper Grid voltage range: 3.3KV / 4.16 KV Maximum current (during switching) 1500 Apk Cooling: Forced Air Dimensions (HxWxD): 9.5 x 19.9 x 25 inches Weight: 95 lbs

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