Load-On Startup, which devices must comply with Load-On Startup?
Types of devices that must comply with " Load-On Startup ".
Some power devices must be operated with load when starting up, otherwise these devices may not function properly or cause damage to the device.
The following are some types of devices that must comply with "Load-On Startup":
1. UPS (Uninterruptible Power Supply) Systems
• Online UPS: Ensure that the inverter can immediately supply power to the load when the power is switched off to avoid power failure.
• Backup UPS (Offline/Standby UPS): When the main power fails, the UPS must be able to start the battery power supply under load to ensure the continuous operation of the load.
2. Generator
• Must be able to start under load, especially in critical areas such as hospitals, data centers, and industrial production.
• Many diesel generators need to ensure stable voltage and frequency when starting so that they can immediately supply power to load equipment.
4. VFD, Variable Frequency Drive
• Motors controlled by VFDs (such as pumps, fans, compressors) which usually need to be started under load conditions to ensure a smooth start-up process without causing damage to the equipment.
5. Solar Inverter
• In a grid-tied or off-grid system, the inverter must be able to start when the load is connected, otherwise the system may not be able to supply power normally.
6. EV Charger
• The power supply equipment of some electric vehicle charging stations needs to ensure that it starts when the load is connected (vehicle is connected) to avoid voltage surges that affect battery charging efficiency.
7. Industrial machinery and automation equipment
• For example, CNC machines, robotic arms, compressors, etc. The control power supply of these devices must ensure a stable startup when the load is connected, to avoid disrupting production operations.
GW Instek AEL Series supports Load-On Startup.
Set the Load-ON angle to match the output voltage phase angle of the DUT.
The operation sequence is as follows:
1. Connect the DUT to the AEL Series AC/DC Load and turn it off.
2. Power on the AEL Series AC/DC Load. Press Config , CONFIG: the sequence is:
EXTIN OFF → SYNC OFF →“LD ON” →“LDOFF” → “BW” → AVG → CPRSP → CYCLE → SNUB.
In the LD ON setting, configure the Load ON angle, which can be set within a range of 0 to 359 degrees.
3. Set the load current.
4. Press Load ON.
5. The DUT outputs or turns on the DUT.
The following figure shows the situation when the DUT is turned on or the output voltage is at 90 degrees and the AEL AC/DC Load angle is also set at 90 degrees.
 |
The output of general power supplies does not have angle control, but even if the angle is different, it does not affect the AEL series' Load-On Startup.
As shown in the figure below, the output voltage and load angle are different.
The following figure shows the situation where the AEL AC/DC Load angle is set to 0 degrees when the DUT is turned on or the output voltage is at 90 degrees.
 |
The following is the Load-On Startup waveform of another brand model 638XX AC electronic load.
 |
Summary
The Load-On Startup design ensures that the equipment can start normally when the load is connected, preventing system crashes, equipment damage, or production interruptions caused by transient current fluctuations or insufficient voltage. This is especially important in critical power supply systems—such as UPS units, generators, and power supplies—as well as in industrial and automation applications.
Overseas Sales Department
Good Will Instrument Co., Ltd
No. 7-1, Jhongsing Road, Tucheng Dist.,
New Taipei City 23678, Taiwan R.O.C.
Email: marketing@goodwill.com.tw