Delta 1.07 VFD-D D - Manual (Page 138)

Appendix B How to Select AC Motor Drive |DD Series
B-4
B-2 General Precautions
Drives Selection
1. When the AC Motor Drive is connected directly to a large-capacity power transformer (600kVA
or above) or when a phase lead capacitor is switched, excess peak currents may occur in the
power input circuit and the converter section may be damaged. To avoid this, use an AC input
reactor (optional) before AC Motor Drive mains input to reduce the current and improve the input
power efficiency.
2. When a special motor is used or more than one motor is driven in parallel with a single AC Motor
Drive, select the AC Motor Drive current ≥1.25x(Sum of the motor rated currents).
3. The starting and accel./decel. characteristics of a motor are limited by the rated current and the
overload protection of the AC Motor Drive. Compared to running the motor D.O.L. (Direct
On-Line), a lower starting torque output with AC Motor Drive can be expected. If higher starting
torque is required (such as for elevators, mixers, tooling machines, etc.) use an AC Motor Drive
of higher capacity or increase the capacities for both the motor and the AC Motor Drive.
4. When an error occurs on the drive, a protective circuit will be activated and the AC Motor Drive
output is turned off. Then the motor will coast to stop. For an emergency stop, an external
mechanical brake is needed to quickly stop the motor.
Parameter Settings
1. The AC Motor Drive can be driven at an output frequency up to 400Hz (less for some models)
with the digital keypad. Setting errors may create a dangerous situation. For safety, the use of
the upper limit frequency function is strongly recommended.
2. High DC brake operating voltages and long operation time (at low frequencies) may cause
overheating of the motor. In that case, forced external motor cooling is recommended.
3. Motor accel./decel. time is determined by motor rated torque, load torque, and load inertia.
4. If the stall prevention function is activated, the accel./decel. time is automatically extended to a
length that the AC Motor Drive can handle. If the motor needs to decelerate within a certain time
with high load inertia that can’t be handled by the AC Motor Drive in the required time, either use
an external brake resistor and/or brake unit, depending on the model, (to shorten deceleration
time only) or increase the capacity for both the motor and the AC Motor Drive.