DC Bus Condition Attributes

These are Motion Control Axis attributes associated with the DC Bus including functionality to address both under-voltage and over-voltage conditions.

DC Bus Input Current

Measured DC Bus current flowing into a drive device. For a drive device with multiple inverter axis instances, this DC Bus Input Current represents the total current supplied by the DC Bus to all the inverters within the device. The DC Bus Input Current also may include DC Bus current passing through the drive device to additional downstream drive devices connected to the common DC Bus in a daisy-chain configuration.

DC Bus Voltage

Measured DC Bus Voltage. For inverters and DC Converter Types, the DC Bus measured is an input to the device. For all other Converter Types, the DC Bus measured is an output of the device.

DC Bus Voltage - Nominal

Normal DC Bus Voltage during operation as determined by averaging the DC Bus Voltage over a device specific time interval. This value is used as the basis for Bus Overvoltage and Undervoltage limits.

For inverters and DC Converter Types, the DC Bus measured is an input to the device. For all other Converter Types, the DC Bus measured is an output of the device.

Bus Regulator Reference

The Bus Regulator Reference attribute returns the current turn on voltage threshold for the bus regulator.

Bus Regulator Voltage Level

The Bus Regulator Voltage Level attribute sets the DC Bus voltage level for the DC Bus Regulator when the Bus Regulator Set Point Source is set to Bus Regulator Voltage Level.

Bus Regulator Set Point Source

The Bus Regulator Set Point Source attribute is the enumerated value that determines the source of the DC Bus voltage level to be used by the DC Bus Regulator.The DC Bus Voltage Nominal selection sets the DC Bus voltage level used by the DC Bus Regulator to a vendor specific percentage above the time averaged DC Bus voltage given by the DC Bus Voltage Nominal attribute.

The Bus Regulator Voltage Level selection sets the DC Bus voltage level used by the DC Bus Regulator to the voltage determined by the configured Bus Regulator Voltage Level attribute.

Bus Regulator Kp

The Bus Regulator Kp attribute sets the proportional gain for the DC Bus Regulator.

The DC Bus Regulator is used in cases where the drive does not have the ability to regulate the DC Bus voltage through other means (regenerative converter or shunt regulator) while the motor is decelerating and driving energy into the DC Bus. It does this by limiting the amount of torque producing current, Iq, and thereby limiting the deceleration rate of the motor to keep the DC Bus voltage under the level that produces a DC Bus overvoltage condition.

When actively limiting current, the Current Limit Source attribute indicates Bus Regulator Limit.

The DC Bus Regulator is only applicable when the Bus Regulator Action attribute is set to either Adjust Frequency or Both – Frequency First.

Bus Regulator Ki

The Bus Regulator Ki attribute sets the integral gain for the DC Bus Regulator.

Bus Limit Regulator Kp

The Bus Limit Regulator Kp attribute sets the proportional gain for the DC Bus Limit Regulator.

The DC Bus Regulator is used in cases where the drive does not have the ability to regulate the DC Bus voltage through other means (regenerative converter or shunt regulator) while the motor is decelerating and driving energy into the DC Bus. It does this by limiting the rate of change of the velocity reference signal into the frequency control function of the drive. When used with the Bus Limit Active Current regulator, this regulator keeps the DC Bus voltage under the level that produces a DC Bus overvoltage condition.

The DC Bus Limit Regulator is only applicable when the Bus Regulator Action attribute is set to either Adjust Frequency or Both – Frequency First.

Bus Limit Regulator Kd

The Bus Limit Regulator Kd attribute sets the derivative gain for the DC Bus Limit Regulator

Bus Limit Active Current Regulator Kp

The Bus Limit Active Current Regulator Kp attribute sets the proportional gain for the DC Bus Limit Active Current Regulator.

The DC Bus Limit Active Current Regulator is used in cases where the drive does not have the ability to regulate the DC Bus voltage through other means (regenerative converter or shunt regulator) while the motor is decelerating and driving energy into the DC Bus. It does this by adjusting the output frequency in response to error in the active (torque producing) current. When used with the Bus Limit regulator, this regulator keeps the DC Bus voltage under the level that produces a DC Bus overvoltage condition.

The DC Bus Limit Active Current Regulator is only applicable when the Bus Regulator Action attribute is set to either Adjust Frequency or Both – Frequency First.

Bus Limit Active Current Regulator Ki

The Bus Limit Active Current Regulator Ki attribute sets the integral gain for the DC Bus Limit Active Current Regulator.

External Bus Capacitance

The External Bus Capacitance attribute represents the external DC Bus capacitance when the associated AFE converter or drive acts as a Bus Master, supplying DC Bus power to one or more Common Bus Followers. This attribute might also be applicable to standalone AFE converters that allow connection to an external capacitor.

Bus Configuration

The Bus Configuration attribute is an enumerated selection that specifies how the DC Bus is used.

Standalone specifies that DC Bus power supplied by the drive's converter section is applied only to this drive’s power structure.

Shar

e

d AC/DC specifies that the converter associated with this CIP Motion device is to supply and share DC Bus power with other drives. This would typically result in de-rating of the converter’s continuous current rating when there are multiple converter devices paralleled in a bus sharing group.

Shared DC specifies that this drive is sharing DC bus power generated by another Shared AC/DC or Shared DC/DC CIP Motion drive, or external Non-CIP converter. Shared D

C axes gene

rally participate in a bus sharing group.

Shared DC - Non CIP Converter specifies that this drive is receiving DC bus power generated by an external AC/DC converter that is not CIP Motion compliant and distributing its DC bus power to other CIP Motion drives. A drive configured for Shared DC - Non CIP Converter is responsible for communicating the status of the external converter to the control system as if the external converter were integrated with the drive. Specifically, this communication includes the DC Bus Up and DC Bus Unload status bits reflecting the current state of associated external converter.

Shared DC/DC specifies that the converter associated with this CIP Motion device supplies and shares DC bus power with other Shared DC devices. DC/DC converters may convert input power from a primary DC bus, generally supplied by a Shared AC/DC converter, to a secondary DC bus output at a different voltage level supplying one or more Shared DC drives. It may also simply distribute primary DC bus power from a Shared AC/DC converter to multiple Shared DC drives on a secondary DC bus without any conversion. A Shared DC/DC converter has a unique capability in that it can be both a bus master for a bus group and a bus slave in a different bus group. Thus, Shared DC/DC axes generally participate in two bus sharing groups.

Bus Voltage Select

The Bus Voltage Select value indicates the expected bus voltage level of the drive application. High bus voltage selection is usually associated with drive running on the North American power grid, while operating in Europe a Low Bus Voltage selection would be appropriate. This parameter can be used to compensate for these different bus voltage levels in the current loop.

Bus Regulator Action

The Bus Regulator Action attribute controls the method of operation of the DC Bus Regulator that addresses the regenerative over-voltage conditions that can occur when decelerating a motor. If Disabled, no regulation is applied to the DC Bus level by this device to control regenerative energy sourced by the motor. When Shunt Regulator is selected the associated shunt regulation hardware is applied to the DC Bus to dissipate regenerative energy via an internal or external resistor. When controlling Induction Motors, additional bus regulation methods are available that do not require a shunt regulator. When Adjust Frequency is selected, the output frequency of the device is controlled relative to the speed of the motor to control the amount of regenerative energy pumped into the DC Bus. Different sequential application of shunt regulation and frequency control can be applied to motor. When Bus Follower is selected, the DC Bus is generated by an external converter rather than an integral converter. No bus regulation is applied to the DC Bus level and the drive does not generate an exception if the DC Bus is still active when the DC Bus contactor of the integrated converter is open. In this context, the integral converter is not connected to AC power.

Regenerative Power Limit

The Regenerative Power Limit attribute limits the amount of power allowed to transfer between the motor and the DC Bus during regenerative braking of the motor load. Since this is regenerative power, the value of the limit is negative.

Converter Regenerative Power Limit

The Converter Regenerative Power Limit attribute limits the amount of regenerative power allowed to transfer from the DC Bus to the converter. Since this is regenerative power, the value of the limit is negative.

Converter Rated is defined as the Converter Rated Input Power attribute value.

When the Bus Voltage Reference Source is configured for Dynamic Bus Control (DBC), this attribute sets the maximum regenerative power the converter is allowed to transfer to the AC line while the DC bus voltage is above the DBC High Voltage Threshold during DBC Regen operation.

Converter Motoring Power Limit

The Converter Motoring Power Limit attribute limits the amount of motoring power allowed to transfer from the AC Line to the motor via the DC Bus.

Converter Rated is defined as the Converter Rated Input Power attribute value.

When the Bus Voltage Reference Source is configured for Dynamic Bus Control (DBC), this attribute sets the maximum motoring power the converter is allowed to transfer to the DC Bus while the DC bus voltage is below the DBC Low Voltage Threshold during DBC Motoring operation.

Shunt Regulator Resistor Type

The Shunt Regulator Resistor Type defines using either the Internal or External Shunt resistor.

External Shunt Regulator ID

The External Shunt Regulator ID is the Rockwell specific identifier for the External Shunt Regulator. A value of 0 indicates use of a custom shunt regulator that requires user configuration.

External Shunt Power

Use the External Shunt Power attribute after configuring the external shunt resistor. The External Shunt Power attribute value specifies the power rating of the external shunt resistor, in Kilowatts.

External Shunt Pulse Power

Use the External Shunt Pulse Power attribute after configuring the external shunt resistor. The attribute value specifies the power for delivering to the external shunt resistor for one second, without exceeding the rated element temperature. There are approximations to help determine this attribute if this information is not available

from your vendor.

Shunt Pulse Power

(Kilowatts) = 75,000 * lbs, where lbs is the weight of the resistor wire element.

Another is that the thermal time constant =

Shunt Pulse Power

(Kilowatts) / 'Shunt Power’ (Kilowatts) sometimes referred to as thermal mass.- the time for the resistor element to reach 63% of rated temperature with applied rated Kilowatts. A third method for determining this value: The pulse Kilowatts for 1 second is twice the watt rating of a 2 second pulse. In other words, the watt*sec rating is a constant if the pulse duration is short compared to the thermal time constant of the resistor and is a function of the element mass.

External Bus Capacitance

The External Bus Capacitance attribute represents the external DC Bus capacitance when the associated converter or drive:

The External Bus Capacitance attribute also is applicable with standalone drives that allow connection to an external capacitor. This attribute is not applicable when the Bus Regulator Action is set to Bus Follower.

External Shunt Resistance

The External Shunt Resistance attribute represents the resistance of the External Shunt Regulator resistor.

Power Loss Action

The Power Loss Action attribute sets the reaction to a DC Bus under-voltage condition when the DC Bus voltage or AC Line RMS voltage drops below a hard-coded threshold in the device or the configured Power Loss Threshold. This provides a specific (configured) response to an incoming power loss while the drive/motor is running.

A

Continue

action selection configures the drive to ignore the power loss condition and continue to run for as long as possible. A Bus Undervoltage exception may occur if the DC Bus Voltage falls below the Factory or User Limits. Otherwise, operation will continue until the low voltage power supplies drop out. There may be concerns operating the power structure below the point where the gate drives start to lose power potentially resulting in damage to the device. The Bus Undervoltage Exception Actions will be set accordingly.

A

Coast Thru

action selection configures the drive to zero the PWM output of the drive while leaving the axis in the Running state. For a drive, this effectively disable power flow to the motor through the devices power structure. If the incoming power returns before the timeout period, given by the Power Loss Time, the drive automatically starts to control the motor again. If, however, the power doesn't return before Power Loss Timeout period expires, a Bus Power Loss exception is generated.

A

Decel Regen

action selection configures the drive to regeneratively charge the DC bus by decelerating the motor using the bus regulator to regulate the bus voltage at a predetermined level. When incoming power is restored the drive returns to normal operation. If, however, the drive reaches zero speed or the Power Loss Time period expires before the incoming power has restored, the drive power structure is disabled and a Bus Power Loss exception is generated.

A

Ride Thru

action selection configures the device to zero the PWM output of the device while leaving the axis in the Running state. For a regenerative converter, this disables regenerative power flow through the devices power structure to the AC line. If the incoming power returns before the timeout period, given by the Power Loss Time, the device automatically restarts PWM modulation. If, however, the power does not return before Power Loss Timeout period expires, a Converter AC Power Loss exception is generated.

Power Loss Threshold

Sets the Level for Power Loss as percent of nominal DC Bus Voltage or nominal AC Line Voltage.

Shutdown Action

Shutdown Action selects the action for the device when a Shutdown Request initiates.

Disable, the default action for a drive, immediately disables the device's power structure according to the Category 0 Stop Sequence. For a regenerative converter, this action immediately disables the converter’s power structure to stop regenerative power flow.

If Drop DC Bus is selected, action can be taken to drop the DC Bus voltage as well. This is generally done by opening an AC Contactor Enable output provided by the device that controls power to the converter.

The Shutdown Action executes the Category 0 Stop Sequence for a drive.

Power Loss Time

When the Power Loss Action is set to Coast Thru, Ride Thru, or Decel Regen, this attribute sets the timeout value before a Bus Power Loss exception is generated by the drive, or a Converter AC Power Loss exception is generated by the converter, in response to a Power Loss condition. For details, see the Power Loss Action attribute table earlier in this topic.

Pre-Charge Hold Control

The Pre-Charge Hold Control attribute controls the axis state transition out of the Pre-Charge state. When set to Enabled by the controller during device initialization, the axis remains in the Pre-Charge state, even after all other pre-charge conditions are met, and remains in the Pre-Charge state until the Pre-Charge Hold Control is set to Disabled by the controller. When this transition from Enabled to Disabled occurs, and all other Pre-Charge conditions are met, the Pre-Charge Hold Delay is applied prior to transitioning out of the Pre-Charge state.

When set to Disabled by the controller during device initialization, the normal axis state transition out of Pre-Charge occurs when pre-charge conditions are met.

This attribute allows programmable control of the completion of the pre-charge function and may be used to coordinate the pre-charge of a system with multiple converters and drives.

Pre-Charge Hold Delay

When entering the Pre-Charge state with Pre-Charge Hold Control Enabled, the Pre-Charge Hold Delay attribute determines the delay time after the Pre-Charge Hold Control is set to Disabled (assuming all other pre-charge conditions are met) before the axis state is allowed to transition out of the Pre-Charge state.

This attribute has no effect on Pre-Charge state transition if entering the Pre-Charge state with Pre-Charge Hold Control Disabled.

Use this configurable delay to control the sequence of pre-charge completion of a system with multiple converters and drives.