Hitachi L100 Series, Инструкция по эксплуатации

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Frequently Asked Questions
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1–24
Q. Why does the manual or other documentation use terminology such as “200V
class” instead of naming the actual voltage, such as “230 VAC?”
A. A specific inverter model is set at the factory to work across a voltage range
particular to the destination country for that model. The model specifications
are on the label on the side of the inverter. A European 200V class inverter
(“EU” marking) has different parameter settings than a USA 200V class
inverter (“US” marking). The initialization procedure (see
“Restoring
Factory Default Settings” on page 6–8 ) can set up the inverter for European
or US commercial voltage ranges.
Q. Why doesn’t the motor have a neutral connection as a return to the inverter?
A. The motor theoretically represents a “balanced Y” load if all three stator
windings have the same impedance. The Y connection allows each of the
three wires to alternately serve as input or return on alternate half-cycles.
Q. Does the motor need a chassis ground connection?
A. Yes, for several reasons. Most importantly, this provides protection in the
event of a short in the motor that puts a hazardous voltage on its housing.
Secondly, motors exhibit leakage currents that increase with aging. Lastly, a
grounded chassis generally emits less electrical noise than an ungrounded
one.
Q. What type of motor is compatible with the Hitachi inverters?
A. Motor type – It must be a three-phase AC induction motor. Use an inverter-
grade motor that has 800V insulation for 200V class inverters, or 1600V
insulation for 400V class.
Motor size – In practice, it’s better to find the right size motor for your
application; then look for the inverter to match the motor.
NOTE: There may be other factors that will affect motor selection, including heat dissi-
pation, motor operating speed profile, enclosure type, and cooling method.
Q. How many poles should the motor have?
A. Hitachi inverters can be configured to operate motors with 2, 4, 6, or 8 poles.
The greater the number of poles, the slower the top motor speed will be, but
it will have higher torque at the base speed.
Q. Will I be able to add dynamic (resistive) braking to my Hitachi L100 drive after the
initial installation?
A. Yes. You can connect a dynamic braking unit to the L100 inverter. The
resistor in the braking unit must be sized to meet the braking requirements.
More information on dynamic braking is located in Chapter 5.