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Frequently Asked Questions

Geting Started

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 dissipation, 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 SJ300 drive after the initial installation?

A.Yes. Models SJ300-004XXX through SJ300-110XXX have built-in dynamic braking units. You can add an external resistor to these models to improve braking perfor- mance. Models SJ300-150XXX through SJ300-1500XXX require you to add an external braking unit. The braking resistor connects to the external braking unit for those models. More information on dynamic braking is located in Chapter 5.

Q.How will I know if my application will require resistive braking?

A.For new applications, it may be difficult to tell before you actually test a motor/drive solution. In general, some applications can rely on system losses such as friction to serve as the decelerating force, or otherwise can tolerate a long decel time. These applications will not need dynamic braking. However, applications with a combina- tion of a high-inertia load and a required short decel time will need dynamic braking. This is a physics question that may be answered either empirically or through exten- sive calculations.

Q.Several options related to electrical noise suppression are available for the Hitachi invert- ers. How can I know if my application will require any of these options?

A.The purpose of these noise filters is to reduce the inverter electrical noise so the operation of nearby electrical devices is not affected. Some applications are governed by particular regulatory agencies, and noise suppression is mandatory. In those cases, the inverter must have the corresponding noise filter installed. Other applications may not need noise suppression, unless you notice electrical interference with the opera- tion of other devices.

Q.The SJ300 features a PID loop feature. PID loops are usually associated with chemical processes, heating, or process industries in general. How could the PID loop feature be useful in my application?

A.You will need to determine the particular main variable in your application the motor affects. That is the process variable (PV) for the motor. Over time, a faster motor speed will cause a faster change in the PV than a slow motor speed will. By using the PID loop feature, the inverter commands the motor to run at the optimal speed required to maintain the PV at the desired value for current conditions. Using the PID loop feature will require an additional sensor and other wiring, and is considered an advanced application.