In Okuma’s Motion Control System there two parts that run the system. They are the DC power supply unit and the MIV inverter unit.

Today we will be highlighting the MIV inverter unit specifically for Servo axis uses. MIV Servo drives are connected in series with the power supply and MIV Spindle drive using a converter link. This link allows the MIV Servo drives to communicate with the rest of the system. The MIV Servo drives also come in two types: One-axis and Two-axis drives. This means that the MIV unit can control either one axis or it can control two axes based on the configuration of the drive. MIV drives come in a variety of capacities that range from 1.0kW to 45kW. MIV Servo drives control two types of motors: BL Servo Motors and PREX Servo Motors. BL Motor drives are designated by the letter “B” at the end of the model number whereas PREX Motors have the letter “P” at the end.

Some common errors and alarms with these drives are El-13, AL-03, and AL-12. EL-13 is an exception error. Exception errors are different than normal alarms. They usually point to a specific problem with the MIV unit. In this case, EL-13 is an Inverter Bridge Error. This error usually points to shorted output transistors and is a sign that the drive should be sent in for repair because there could be other damage to the drive because of the transistors being bad. AL-03 is an alarm for Inverter DC Bus Voltage. This means that the DC bus voltage that is linked between all drives in the system is either too high (Overvoltage) or too low (Undervoltage). This can stem from a couple of sources. This alarm could indicate that your input power is too low or too high, the power supply is bad, or the MIV drive is bad. In this case, we suggest checking input power, swap out the power supply or the MIV drive, or send in the power supply or MIV drive for repair. AL-12 is an alarm for Encoder Initialization Error. This means that when initializing the encoder of the motor detects an error. In this case, there are a couple of things to check. First, you need to check if the encoder cable is not shorted or broken anywhere because this can cause this alarm. Next would be to have motor swapped with another motor or encoder because this will narrow down if it is an encoder error or a MIV drive error. This can be a drive error because there is some circuitry on the control board of the MIV drives that is specific to the encoder and if that fails then it will produce this alarm.

At Precision Zone, we guide our clients toward the best decisions that serve their business needs. If you have specific repair or replacement questions, get in touch with our expert customer support team at 800-551-4420 or

Written by:

Marketing & Creative Director at IcarTeam, and supporting afiliated businesses,
including Precision Zone, Precision Education Integrators and Alfra Tools.
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