Drives come standard with electronic thermal overload protection allowing the VFD to deliver 150% of the rated output current for 1 minute and higher current levels for shorter periods. VFDs have an adjustable overload parameter to protect the motor. In the aforementioned scenario, assuming the motor’s full load amp (FLA) rating is 12 A, the VFD’s overload parameter should be set to 12 A divided by 29 A, or 42%, plus additional derating that may be required for the application. The motor overload parameter for the drive should be set according to the drive’s true output rating, not the derated value. Therefore, the motor overload parameter must be scaled to limit output current. Drive software doesn’t recognize input power as single-phase. The input current rating for the drive remains the same. For example, a 10 hp, 240 V drive is typically rated at 29 A continuous current, but the derated output current will be half, or 14.5 A, because of the single-phase input to the drive. When derating, double the current but not the horsepower rating. However, it is important to be aware that single-phase power will cause higher dc bus voltage ripple.įor proper drive sizing, the output current should be derated by 50%. Most 3-phase drives up to 30 hp at 240 V, 60 hp at 480 V, and 60 hp at 590 V input can have single-phase power applied. If ratings are exceeded, a larger 3-phase drive is required when using single-phase input voltage. Depending on the horsepower and voltage rating, drives can accept single-phase input voltage without derating the output current. Single-phase input voltage on a VFD with 3-phase input is common in many automation applications. Preventing faults and failures starts by right-sizing the VFD for the machine task. Identifying a fix may be simple or reveal a complex problem, which is why fault and failure prevention is always the best strategy. Operators must quickly identify and resolve problems. Conversely, faults and failures can escalate into costly downtime. Properly sized and configured VFD systems can help optimize performance, save energy, and permanently lower machine and robotic lifecycle costs. The addition of a scaling pot will provide for proportional follower operation.Variable frequency drive (VFD) technologies support an expansive range of machine tasks and robotics in automated warehouses, logistics, manufacturing, and process industries. By simply connecting the input terminals across the armature leads of a “master motor”, you can use the VSI2 for master/follower operation. The wide input range allows the VSI2 to follow signals as low as +0-5V logic levels and up to the 180VDC levels present at the armature leads of a 180VDC motor. The output of the VSI2 is a filtered, pulse width modulated signal that is directly proportional to the input speed signal. The Dart VSI2 can be used with virtually any motor speed control that has a speed reference circuit of +5 to +15VDC and an input impedance greater than 47K ohms. An electrical isolation rating of 2500Vrms is achieved by the use of an optically isolated IC package. The VSI2 is packaged in an aluminum chassis mount housing and contains an on-board power supply for its logic circuit. A single model accepts a wide range of input voltages (0-5 through 0-25VDC or 0-25 through 0-250VDC) AND 4-20mA. The VSI2 incorporates Dart’s unique feedback circuit, which virtually eliminates output changes due to the thermal drift of logic components. The Dart VSI2 (speed signal isolator) permits the user to control the output of a variable speed motor drive from any external grounded or ungrounded DC input signal. VSI2 – Signal Follower Option NEW – Jumper Selectable DC volts or 4-20mA Operation
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