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FREQUENTLY ASKED LOAD QUESTIONS

How are the maximum ratings of the dc electronic load determined?
Can the loads be field calibrated?
Can the dc electronic load operate at 0 Volts?
Other electronic load manufacturer’s use slew rate in their specifications,
       why does AMREL use slew time?
Can I parallel ten 600W loads together to test a 6kW power supply?
How are paralleled single loads different than pre-built high power loads?
I need to perform external analog programming or ac modulation, how do I do this?
What kind of programmable protections are available on the eLOAD?
Does the eLOAD offer soft-start features?
Can I switch operating mode ranges while input is on?
Does the eLOAD offer different power-on settings to be saved?
How is the accuracy calculated for CR mode?
What does the resolution on the specification sheet mean?
What does the accuracy on the specification sheet mean?
What is Port 0?
Is there an external method for shutting off the eLOAD input?
Does the water-cooled eLOAD offer an anti-condensation feature?

How are the maximum ratings of the DC Electronic Load determined?

The ratings can be easily determined by the model number. For example, we have a model PLA800-60-300.  The “PLA” indicates the type of load, whether it is air-cooled, water-cooled or low profile.  The 800 indicates the maximum power you can dissipate.  The “60” is the maximum Voltage and the “300” is the maximum current.  Although, the 60V/300A max ratings theoretically equate to 18KW, the maximum power is limited by the max power specified, in this case 800Watts. You cannot exceed the power rating of the load, otherwise damage to the load will occur.

 

Can the loads be field calibrated?

Yes, the calibration is done via the keypad or PC control interface, with the use of a properly rated shunt voltage/current source, and DMM.   It is recommended that the load be calibrated once a year. 

 

Can the dc electronic load operate at 0 Volts?

AMREL's dc electronic loads require a minimum voltage level to operate at full current capacity. The minimum voltage varies by model and can range anywhere from 0.4V to 5V for full power dissipation, depending on the maximum ratings of the load. However, the load will operate all the way down to 0V at a de-rated current. See specifications for individual units for operational graphs. To test a DUT at zero volts, a boost power supply rated for the required testing current and the compliance voltage to cover the minimum operating voltage, is needed. Also take into consideration the voltage drop induced by the power cable, which would require a higher minimum operating voltage.

 

Other dc electronic load manufacturer’s use slew rate in their specifications, why does AMREL use slew time?

Slew time is actually the time portion of the slew rate.  Slew rate is defined as: Change in Value where Value can be current, voltage, resistance or power.  Slew Time Period time allows programming of the time period to reach the designated value for the range and mode.  Based on the main level setting, transient level setting and the slew time setting, the slew rate can be calculated accordingly.  Slew time is basically a more precise method of controlling the rise and fall time of current, voltage, resistance or power during transient operation.

 

Can I parallel ten 600W loads together to test a 6kW power supply?

It is generally recommended to parallel the eLOAD for power supply testing when the objective is to share the current.  Paralleling the eLOAD in other operating modes such as CR and CV will work properly, however the timing and setting of each eLOAD will then become critical.

 

How are paralleled single loads different than pre-built high power loads?

AMREL’s high power loads have synchronized hardware control signals to control each individual load in the system.  Therefore, the control signal timing discrepancy between each individual load is minimized.  Furthermore, high power eLOAD’s are calibrated and tuned as an overall unit, to guarantee equal load sharing between each individual load bank.  However, paralleled single loads have different timing signals due to the non-conformity of the loads and the load sharing will be harder to manage.  The cabling, water distribution (PLW), and control synchronization are important factors to consider. 

 

I need to perform external analog programming or ac modulation, how do I do this?

The external control function allows the load’s main level voltage, current, power and resistance max range setting to be scaled from 0 to 10 Volts.  Once the external control is enabled, the voltage (0~10V) inputted through the EXT_PRG and EXT_GND port will adjust the current, voltage, resistance or power level accordingly.  

The eLOAD offers external programming support for ac voltage range of -1V ~ 10V and frequency range of dc ~ 10 kHz.

 

What kind of programmable protections are available on the eLOAD?

Over-current, over-voltage, over-power, under-current, under-voltage, under-power are available.

 

Does the eLOAD offer soft-start features?

The eLOAD offers two layers of soft-start protection.  The turn-on sequence for each mode and range is designed to minimize current overshoot and system instability.  For more sensitive applications, an “under -voltage protection” (V-On Control) feature is available.  The V-On control will prevent the load from turning on until a voltage threshold is reached.  The V-On Voltage is adjustable depending on the application and can be used to simulate different types of testing.

 

Can I switch ranges while the input is on?

The eLoad has three overlapping operating ranges in each mode.  As part of our factory default settings, when switching from one range to another range in manual mode (i.e. CV Low to CV High), the final switched state will have the input turned off.  If an application requires the input to stay on when switching ranges, the option “cross range” must be changed from “input off” to “input remain.”  By changing the option, the load will switch ranges while keeping the input on, to accommodate the different DUT applications.  By changing the option, the user can effectively switch between ranges based on the application needed by the DUT. Cross range operation will work under both “manual” and “auto” range control mode.

 

Does the eLOAD offer different power-on settings to be saved?

There are four end-user defined profiles that can be saved in locations 0, 1, 2, and 3.

The factory default profile is stored in location 0 and 3 and can be loaded any time to restore the load to default settings.  The syntax profile stored in location 2 will configure the load to become PEL command compatible.

 

How is the accuracy calculated for CR mode?

To calculate accuracy for CRM and CRH mode, please follow the procedures below.

1)       Convert Rset to mS units > mSset (Resistance value in mS units).

2)       Calculate %error in mS units.

3)       Calculate mSset + %error + Offset.

4)       Calculate mSset + %error – Offset.

5)       Convert both values back to resistance values to obtain accuracy range.

 

What does the resolution on the specification sheet mean?

Resolution is the minimum numerical increment or decrement of the voltage, current, resistance and power setting that can be programmed into the load or displayed by the load.  If the setting is incremented or decremented by a numerical value below the resolution specifications, the eLOAD may not respond to the entry.  AMREL specifications guarantee 14 bit resolution for all ranges and modes.   

 

What does the accuracy on the specification sheet mean?

The accuracy is the maximum deviation from the programmed or read back value.

 

What is Port 0?

A general purpose output port that generates a TTL compatible signal; active high (5V) when port is on and inactive low (0V) when port is turned off. The PORT 0 feature can be used to control external devices such as a dc contactor or a relay. To enable PORT 0, simply follow LOAD CONTROL > PORT 0 > ON.


Is there an external method for shutting off the eLOAD input?

Short the remote inhibits (RI) rear terminal connectors. Also an available TTL fault signal will trigger into an active high state, in the case of any fault conditions.

 

Does the water-cooled eLOAD offer an anti-condensation feature?

The eLOAD incorporates an automatic anti-condensation, liquid cooling system.

 

For more information:

You may contact AMREL via e-mail at pdinfo@amrel.com or by phone:
U.S. only (800) 654-9838 or Intl' (626) 443-6818
fax: (626) 443-8600


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