4. Features and Functions

4.1. Set-Points

4.2. Commands

The ALx Series MagnaLOAD features a variety of commands, which can all be accessed from the front panel, external user I/O, and computer interface.

4.2.1. Start

The Start command engages the MagnaLOAD‘s DC input to allow the product to begin dissipating power, transitioning the status from Disabled to Enabled. The Start command switches the dissipative elements out of the DC circuit using a high speed switching device. Upon issuing the Start command, the transition time from Disabled to Enabled is ## ms.

4.2.2. Stop

The Stop command disengages the MagnaLOAD‘s DC input to stop the product from dissipating power, transitioning the status from Enabled to Disabled. The Stop command switches the dissipative elements out of the DC bus using a high speed switching device. Upon issuing the Stop command, the transition time from Enabled to Disabled is ## ms.

Warning

Even when the Stop command is issued and the MagnaLOAD‘s status is Disabled, there could still be hazardous voltages on the DC input from an externally connected DC source. Ensure that all instrument connections, load wiring, and load connections are either insulated or covered so that no accidental contact with lethal output voltages can occur. Always use a voltmeter to test the DC bus before making any connections.

4.2.3. Clear

The Clear command removes the latch that disables the input when a fault condition is detected. All conditions that generate the fault must be resolved before the latch can be cleared. Once the fault has been cleared, the input can be re-enabled with the Start command.

4.2.4. Lock

The Lock command secures settings by locking the MagnaLOAD, preventing changes to set-points and configuration settings. When the MagnaLOAD is locked, the front panel Lock button is back-lit red. In addition, the Lock status can be configured as one of the external user I/O digital outputs or queried by computer interface.

4.3. Functions

Functions feature and documentation coming soon

4.4. Operating Profile

With its combination of resistor and linear elements, the ALx Series MagnaLOAD has a unique operating profile as indicated in the figure below. This operating profile figure applies to all ALx Series models, normalized about the model’s maximum voltage, current, and power ratings.

Figure 20: Normalized ALx Series Operating Profile

In the event the user programs the unit to operate in region outside the operating curve, the MagnaLOAD will automatically limit its throughput to prevent any possible damage. This internal limiting will be indicated on the front panel auxiliary display, on the message line as: Operating profile limit reached.

4.5. Control Modes

The ALx Series MagnaLOAD automatically selects the appropriate regulation state depending on the selected control mode, programmed set-points and the voltage and current being driven by the connected DC source. The MagnaLOAD preferences regulation states depending on the selected Control Mode: Voltage Mode, Current Mode, Power Mode, or Resistance Mode.

Control Modes can be selected from the front panel menu system or by computer command. Changing the Control Mode while the DC input is enabled will cause the MagnaLOAD to stop processing power and enter Disabled status.

4.5.1. Voltage Mode

When Voltage Mode is selected, the MagnaLOAD will auto-crossover between voltage, current, and power regulation, but will preference constant voltage regulation over all other states. In Voltage Mode, the MagnaLOAD will try to sink enough current to maintain the voltage set point in a constant voltage regulation state, acting like a shunt voltage regulator. The operating region for Voltage Mode is further described by Figure 21. Programming a resistance set-point is disabled in Voltage Mode as the resistance regulation state conflicts with the voltage and current regulation states.

Trip-point settings for voltage, current, and power can also be used to shutdown the MagnaLOAD when a programmed threshold is crossed.

Caution

Configuring the MagnaLOAD for Voltage Mode while the connected DC source is also trying to regulate voltage will produce regulation instabilities. Instead, an alternative control mode should be selected.

Figure 21: Simplified Voltage Mode Operation Diagram. Refer to Figure 20 for operating profile constraints.

4.5.2. Current Mode

When Current Mode is selected, the MagnaLOAD will auto-crossover between voltage, current, and power regulation, but will preference constant current regulation over all other states. In Current Mode, the MagnaLOAD will allow the input voltage fluctuate while trying to maintain the current set-point in a constant current regulation state. The operating region for Current Mode is further described by Figure 22. Programming a resistance set-point is disabled in Current Mode as the resistance regulation state conflicts with the voltage and current regulation states.

Trip-point settings for voltage, current, and power can also be used to shutdown the MagnaLOAD when a programmed threshold is crossed.

Caution

Configuring the MagnaLOAD for Current Mode while the connected DC source is also trying to regulate current will produce regulation instabilities. Instead, an alternative control mode should be selected.

Figure 22: Simplified Current Mode Operation Diagram. Refer to Figure 20 for operating profile constraints.

4.5.3. Power Mode

When Power Mode is selected, the MagnaLOAD will auto-crossover between voltage, current, and power regulation, but will preference constant power regulation over all other states. In Power Mode, the MagnaLOAD will allow the input voltage and current fluctuate while trying to maintain the power set-point in a constant power regulation state. The operating region for Power Mode is further described by Figure 23. Programming a resistance set-point is disabled in Current Mode as the resistance regulation state conflicts with the voltage and current regulation states.

Trip-point settings for voltage, current, and power can also be used to shutdown the MagnaLOAD when a programmed threshold is crossed.

Caution

Configuring the MagnaLOAD for Power Mode while the connected DC source is also trying to regulate power will produce regulation instabilities. Instead, an alternative control mode should be selected.

Figure 23: Simplified Power Mode Operation Diagram. Refer to Figure 20 for operating profile constraints.

4.5.4. Resistance Mode

When Resistance Mode is selected, the MagnaLOAD will preference Constant Resistance (CR) regulation state over all other regulation states. The MagnaLOAD will operate in constant resistance regulation within the set-point boundaries indicated in grey in Figure 24. If the connected DC source drives the DC bus to one of the bounding set-point limits, the MagnaLOAD will auto-crossover to the appropriate regulation state. To avoid auto-crossover, the bounding set-point limits should be set sufficiently high to increase the constant resistance operating range. trip-point-settings for voltage, current, and power can also be used to shutdown the MagnaLOAD when a maximum desired limit is reached.

Figure 24: Simplified Resistance Mode Operation Diagram. Refer to Figure 20 for operating profile constraints.

4.5.5. Shunt Regulator Mode

Shunt Regulator Mode is designed to regulate the DC bus voltage to ensure the voltage remains below a programmed limit. Shunt Regulator Mode can be used as a replacement for a braking resistor in a DC motor drive application, or as a protection device to prevent rising DC bus voltage from damaging other electronic devices.

When Shunt Regulator Mode is selected, the MagnaLOAD will only dissipate energy when the voltage passes a user-defined voltage threshold. The MagnaLOAD will remain idle at the DC bus voltage defined by the source until that DC bus voltage rises above a programmed voltage threshold. When DC bus voltage passes this voltage threshold, the MagnaLOAD will begin to process power, with the current rising rapidly to the current set point.

The voltage threshold is the programmed voltage set point plus 1% of the unit’s full scale voltage rating. For example, if an ARx7.5-1000-7.5 (7.5 kW, 0-1000 Vdc, 0-7.5 Adc) MagnaLOAD was programmed to 500 Vdc in Shunt Regulator Mode, the MagnaLOAD would begin dissipating energy at the voltage threshold: 500 Vdc + (1% of 1000 Vdc) = 510 Vdc. The MagnaLOAD would continue dissipating energy until the DC bus voltage drops below 500 Vdc.

When the product is dissipating energy in Shunt Regulator Mode, the current is regulated to the MagnaLOAD‘s user-defined current set point.

Note

If the MagnaLOAD is not sized properly for the amount of current fed back onto the DC bus, the voltage on the DC bus may continue to rise beyond the MagnaLOAD‘s voltage threshold.

Figure 25 shows the voltage and current over time in Shunt Regulator Mode, as the DC bus voltage rises below the voltage threshold and the MagnaLOAD begins dissipating energy. trip-point-settings for voltage, current, and power can also be used to shutdown the MagnaLOAD when a maximum desired limit is reached.

Figure 25: Simplified Shunt Regulator Mode Operation Diagram. Refer to Figure 20 for operating profile constraints.

4.6. Regulation States

The ALx Series MagnaLOAD has four regulation states: Constant Voltage (CV), Constant Current (CC), Constant Power (CP), and Constant Resistance (CR). The active regulation state is indicated by a illuminated circular LED next to the respective voltage, current, power, or resistance set-point button. The active regulation state can also be monitored programmatically.

4.6.1. Constant Voltage (CV)

When the constant voltage regulation state is indicated, the MagnaLOAD is maintaining fixed voltage set-point, while the current flucuates with the driving DC source, as illustrated by Figure 26.

Figure 26: Operating range in constant voltage mode

4.6.2. Constant Current (CC)

When the constant current regulation state is indicated, the MagnaLOAD is maintaining a fixed current set-point, while the voltage flucuates with the driving DC source, as illustrated by Figure 27.

Figure 27: Operating range in constant currnet mode

4.6.3. Constant Power (CP)

When the constant power regulation state is indicated, the MagnaLOAD is maintaining a fixed power set-point by varying the current level inversely in response to a change in input voltage, as illustrated by Figure 28.

Figure 28: Operating range in constant power mode

4.6.4. Constant Resistance (CR)

When the constant resistance regulation state is indicated, the MagnaLOAD is maintaining a fixed resistance set-point, by sinking input current linearly proportional the input voltage, as illustrated by Figure 29.

Note

The constant resistance regulation state will only be indicated when the MagnaLOAD is configured for Resistance Mode.

Figure 29: Operating range in constant resistance mode

4.7. Protection and Diagnostics

4.7.1. Over Voltage Trip (OVT)

The ALx Series MagnaLOAD has a programmable Over Voltage Trip setting used to shutdown the product if an undesired maximum voltage value is measured across the DC input. The OVT setting can be adjusted to a maximum of 110% of the specific MagnaLOAD‘s full scale voltage rating. An over-voltage condition must be sustained longer than the OVT/UVT trip delay setting for the OVT fault to register.

When an OVT fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with an OVT alarm shown on the auxiliary display. To resume operation, the DC input voltage must be drop below the MagnaLOAD‘s OVT setting, the function-clear function must be issued, and the input re-energized with the function-start function.

The OVT setting can be programmed through the front panel’s auxiliary display, through one of the four analog inputs, or programmatically through software.

MagnaLOAD products feature a unique input voltage protection scheme, allowing the DC input to sustain voltage tranients 1000 Vdc above the specific MagnaLOAD‘s full scale voltage without damage.

The factory default OVT setting is 110% of the specific MagnaLOAD‘s maximum voltage rating.

4.7.2. Under Voltage Trip (UVT)

The ALx Series MagnaLOAD has a programmable Under Voltage Trip setting used to shutdown the product if an undesired minimum voltage threshold is measured across the DC input. The UVT setting can be adjusted to a minimum of 5% of the specific MagnaLOAD‘s full scale voltage rating. An under-voltage condition must be sustained longer than the OVT/UVT trip delay setting for the UVT fault to register.

The UVT setting was designed to protect DC input sources, such as batteries, from discharging below a minimum desired voltage. If the UVT setting is used, upon first enabling the DC input the DC input voltage must be above the UVT setting or the MagnaLOAD will trip immediately. Figure 30 shows the operating range with both OVT and UVT enabled.

Figure 30: Operating region without trip when OVT and UVT settings are enabled

When an UVT fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with an UVT alarm shown on the auxiliary display. To resume operation, the function-clear function must be issued and the input re-energized with the function-start function.

The UVT setting can be programmed through the front panel’s auxiliary display, through one of the four analog inputs, or programmatically through software.

The factory default UVT setting is 0 Vdc, which disables the UVT protection.

4.7.3. Over Current Trip (OCT)

The ALx Series MagnaLOAD has a programmable Over Current Trip setting used to shutdown the product if an undesired maximum current value is measured through the DC input. The OCT setting can be adjusted to a maximum of 110% of the specific MagnaLOAD‘s full scale voltage rating. An over current condition must be sustained longer than the OCT trip delay setting for the OCT fault to register.

When an OCT fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with an OCT alarm shown on the auxiliary display. To resume operation, the DC input current must be drop below the MagnaLOAD‘s OCT setting, the clear function must be issued, and the input re-energized with the start function.

The OCT setting can be programmed through the front panel’s auxiliary display, through one of the four analog inputs, or programmatically through software.

4.7.4. Over Power Trip (OPT)

The ALx Series MagnaLOAD has a programmable Over Power Trip setting used to shutdown the product if an undesired maximum power value is measured at the DC input. The OPT setting can be adjusted to a maximum of 110% of the specific MagnaLOAD‘s full scale power rating. An over-power condition must be sustained longer than the OPT trip delay setting for the OPT fault to register.

When an OPT fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with an OPT alarm shown on the auxiliary display. To resume operation, the DC input voltage must be drop below the MagnaLOAD‘s OPT setting, the function-clear function must be issued, and the input re-energized with the function-start function.

The OPT setting can be programmed through the front panel’s auxiliary display, through one of the four analog inputs, or programmatically through software.

The factory default OPT setting is 110% of the specific MagnaLOAD‘s maximum power rating.

4.7.5. Thermal Fault

The ALx Series MagnaLOAD has internal thermal switches on its various heatsinks to ensure operation at temperatures within the product’s design parameters. A thermal fault typically results from one of the following conditions:

  • Operating in an environment above the maximum ambient temperature specification
  • Blocking the front panel air intake
  • Internal fan failure

When a thermal fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with a thermal alarm shown on the auxiliary display. To resume operation, the MagnaLOAD‘s internals must cool to a safe operating temperature, the function-clear function must be issued, and the input re-energized with the function-start function.

4.7.6. Interlock

The Interlock functionality allows for remote disabling of the MagnaLOAD into a soft fault state through interruption of a +5V digital reference signal. By default, Interlock functionality is disabled when the MagnaLOAD ships from the factory. Interlock functionality can be enabled from the front panel or computer interface. Once enabled, the external user I/O digital input pin assigned to Interlock (default Pin 24) requires +5V to be present to enable product operation. There are two method to providing +5V to the Interlock digital input:

  • Providing a physical short from the provided external user I/O +5V signal (Pin 14) to the Interlock digital input.
  • Using an external user supplied +5V signal with reference to the external user I/O GND signal (Pin 25).

With either method, an external dry contact may be used to trigger the Interlock functionality.

When the +5V Interlock signal is broken, the dissipative elements are switched out of the DC bus using a high speed switching device, the MagnaLOAD is placed in a soft fault state, and the Lock command is triggered to prevent the user from changing the settings or disabling interlock.

To remove the Interlock fault, the +5V signal must first be restored to the Interlock digital input then the Clear command issued to remove the fault and clear the lock.

4.7.7. User I/O Alarm

The ALx Series MagnaLOAD monitors analog and digital input voltages on the 25-pin User I/O connections to ensure that they are within the each pin’s respective voltage range. A User I/O alarm will be triggered in the event a voltage input on one of these pins exceeds 110% of the specific input’s range, further described by the table below:

User I/O Pins Description Nominal Voltage Range User I/O Alarm Voltage
11, 12, 23, 24 Digital Inputs 0 - 5 V > 5.5 V
5, 6, 17, 18 Analog Inputs 0 - 10 V > 11 V

When an User I/O fault occurs, the DC input bus is disconnected via an internal switching device, leaving the MagnaLOAD in an open-circuit faulted condition with an User I/O alarm shown on the auxiliary display. To resume operation the input voltages on the 25-pin User I/O must return to the each pin’s respective nominal input voltage range, the function-clear function must be issued and the input re-energized with the function-start function.

4.8. Statuses

The MagnaLOAD has various statuses corresponding to its present state of operation. These statuses can be viewed on the front panel, programmatically by computer command, or using the 25-pin user I/O connector. The available statuses are as follows:

Enabled
The MagnaLOAD‘s input is engaged and processing power.
Disabled
The MagnaLOAD‘s input is disengaged and all systems are normal. The MagnaLOAD is awaiting a START command to engage its input. When in a Disabled state, there is an electrical disconnect between the product’s dissipative elements and the DC input terminals through a high speed switching device.
Soft Fault
The MagnaLOAD‘s input is disengaged as a result of a soft fault that occurred. A soft fault occurs when an user-programmed limit is reached, such as a trip setting. A description of the soft fault is displayed on the message line. A soft fault can be cleared with the CLEAR function, placing the MagnaLOAD into a Disabled status. When in a Soft Fault state, there is an electrical disconnect between the product’s dissipative elements and the DC input terminals through a high speed switching device.
Hard Fault
The MagnaLOAD‘s input is disengaged as a result of a hard fault that occurred. A hard fault is a system shutdown resulting from an operating condition that has the potential to damage the product, for example, exceeding the products specifications. A description of the hard fault is displayed on the message line. A hard fault fault can only be cleared by power cycling the product. When in a Hard Fault state, there is an electrical disconnect between the product’s dissipative elements and the DC input terminals through a high speed switching device.

Caution

Ignoring hard faults and repeatedly operating the MagnaLOAD in a manner that triggers a hard fault will eventually result in product damage.

4.9. Messages

The MagnaLOAD has various messages, which elaborate on the product’s present status. A message may indicate normal operation, power limiting as a result of the MagnaLOAD‘s operating profile, or steps to resolve a fault.

Messages for Status: Enabled

  • Systems normal.
  • Operating profile limit reached. Limiting resistor power throughput.
  • Operating profile limit reached. Limiting MOSFET power throughput.

Messages for Status: Disabled

  • System disabled.

Messages for Status: Soft Fault

  • Voltage trip point setting reached. Issue CLEAR command to resume operation in standby.
  • Current trip point setting reached. Issue CLEAR command to resume operation in standby.
  • Power trip point setting reached. Issue CLEAR command to resume operation in standby.
  • Resistance trip point setting reached. Issue CLEAR command to resume operation in standby.

Messages for Status: Hard Fault

  • Global shutdown occurred. Power cycle to resume operation in Standby.
  • Chopper stage currents exceeded product rating. Verify load does not exceed product ratings.
  • Excessive communication errors detected. Check cabling and communications grounding. Contact technical support.
  • Voltage measured that exceeds product’s max rating. Investigate cause and power cycle to resume operation in standby.
  • Current measured that exceeds product’s max rating. Investigate cause and power cycle to resume operation in standby.
  • Power measured that exceeds product’s internal resistive elements’ max rating. Investigate cause and power cycle to resume operation in standby.
  • Resistive elements have exceeded their max temperature rating. Verify adequate cooling air flow and ambient temperature is within product specifications. Power cycle to resume operation in Standby.
  • Linear elements have exceeded their max temperature rating. Verify adequate cooling air flow and ambient temperature is within product specifications. Power cycle to resume operation in Standby.