Line Impedance The Baldor control requires a 1% line impedance minimum . If the impedance of the incoming power does not meet the requirement for the control, a 3 phase line reactor can be used to provide the needed impedance in most cases. Line reactors are optional and are available from Baldor.
The input impedance of the power lines can be determined as follows: Measure the line to line voltage at no load and at full rated load. Use these measured values to calculate impedance as follows:
%Impedance + | (VoltsNo Load Speed * | VoltsFull Load Speed) | 100 | ||
(VoltsNo Load Speed) |
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Line Reactors Three phase line reactors are available from Baldor. The line reactor to order is based on the full load current of the motor (FLA). If providing your own line reactor, use the following formula to calculate the minimum inductance required.
L + | (VL* | L | 0.03) |
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(I | 3 | 377) |
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Where: L | Minimum inductance in Henries. | |||||
Input volts measured line to line. | ||||||
0.03 |
| Desired percentage of input impedance. | ||||
I | Input current rating of control. | |||||
377 |
| Constant used with 60Hz power. | ||||
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| Use 314 if input power is 50Hz. | ||||
Load Reactors Line reactors may be used at the control output to the motor. When used this way, they are called Load Reactors. Load reactors serve several functions that include:
SProtect the control from a short circuit at the motor.
SLimit the rate of rise of motor surge currents.
SSlowing the rate of change of power the control delivers to the motor. Load reactors should be installed as close to the control as possible. Selection should be based on the motor nameplate FLA value.
Power Disconnect A power disconnect should be installed between the input power service and the control for a fail safe method to disconnect power. The control will remain in a
Protective Devices Recommended fuse sizes are based on the following: 115% of maximum continuous current for time delay.
150% of maximum continuous current for Fast or Very Fast action.
Note: These general size recommendations do not consider harmonic currents or ambient temperatures greater than 40° C.
Be sure a suitable input power protection device is installed. Use the recommended fuses and wire sizes shown in Table
Reduced Input Voltage Derating All power ratings stated in Section 6 are for the stated nominal AC input voltages (230 or 460VAC). The power rating of the control must be reduced when operating at a reduced input voltage. The amount of reduction is the ratio of the voltage change.
MN735 |