Chroma's 63800 Series AC&DC Electronic Loads are design for testing uninterruptible power supplies(UPS), Off-Grid Inverters, AC sources and other power devices such as switches, circuit breakers, fuses and connectors.

The Chroma 63800 Loads can simulate load conditions under high crest factor and varying power factors with real time compensation even when the voltage waveform is distorted. This special feature provides real world simulation capability and prevents overstressing thereby giving reliable and unbiased test results.

The 63800's state of the art design uses DSP technology to simulate non-linear rectified loads with its unique RLC operation mode. This mode improves stability by detecting the impedance of the UUT and dynamically adjusting the load's control bandwidth to ensure system stability.

Comprehensive measurements allow users to monitor the output performance of the UUT. Additionally, voltage & current signals can be routed to an oscilloscope through analog outputs. The instrument's GPIB/RS232 interface options provide remote control & monitor for system integration. Built-in digital outputs may also be used to control external relays for short circuit (crowbar) testing.

Chroma's 63800 Loads feature fan speed control ensuring low acoustic noise. The diagnosis/protection functions include selfdiagnosis routines and protection against overpower, over-current, over-voltage and overtemperature.

Chroma's 63800 AC & DC Electronic Load is designed for both AC & DC Load Simulations. Illustrated below are the various load modes which are available:

The Model 63800 AC & DC Electronic Load provides two unique operating modes for AC load simulation: Constant Load Modes and Rectified AC Load Modes. Each are described below.

Constant Load Modes

The Constant Load Modes allow users to set the following operating modes: CC, CR and CP mode. The CC & CP modes in this category allow users to program PF or CF, or both. For CR mode the PF is always set to 1. The power factor range is limited based on crest factor programmed (Shown as Figure 1). If the programmed PF is positive then the current will lead the voltage waveform and when PF is set negative, the current will lag the voltage waveform. (See below)

As seen in Figure 1, for a crest factor of 1.414, the programmed power factor can only be 1 if the input voltage is a sine-wave. However, for a CF of 2.0, the acceptable PF ranges from 0.608 to 0.85; for CF = 3, the PF can then be set from 0.211 to 0.6, etc. So, higher crest factors enable a wider range of power factors.

Rectied AC Load Modes

The 63800 AC/DC Electronic Load provides unique capability to simulate non-linear rectified loads for a wide range of testing applications. There are three load modes available for rectified load simulations: RLC, CP and Inrush Current.

▲ Figure 2: Typical Rectified Circuit

Figure 2 shows the typical model of a rectifier input. Under RLC mode, users can set the RLC values to 100% and simulate the behavior of the actual UUT. Figure 3 & 4 compares the voltage and loading waveforms between the actual RLC built circuit and the simulated rectified circuit by using Chroma's RLC load mode. The waveform obtained under CC mode with the same loading crest factor shown in Figure 5.

▲ Figure 3: Actual RLC Circuit

▲ Figure 4: Simulated RLC Mode

▲ Figure 5: CC Mode

▲ Figure 6: Inrush Current Mode

For inrush current simulation (See Figure 6), the 63800 provides an Inrush Current mode that allows the user to set different inrush current amplitude and voltage phase angle where the inrush current started.

Chroma's 63800 DC load simulation includes four load modes : constant current, constant resistance, constant voltage and constant power as depicted below.

CC, CR, CP mode can be used for regulated voltage power supply testing. For battery charger, CV mode may help to check its current regulation. Many inverter designs, although its input is DC, show an input current and will show rectified pattern. This unique load mode makes the Chroma 63800 load ideal for Fuel Cell, PV module/array and Battery testing.

Chroma's 63800 Series AC & DC Electronic Loads include built-in 16-bits precision measurement circuits to measure the steady-state and transient responses for true RMS voltage, true RMS current, true power(P), apparent power(S), reactive power(Q), crest factor, power factor, THDv and peak repetitive current. In additional to these discrete measurements, two analog outputs, one for voltage and one for current, are provided as a convenient means of monitoring these signals via an external oscilloscope.

Timing Measurement

Timing parameters are critical to many products such as UPS's Breakers and Fuses. The 63800 AC & DC Load also includes a unique timing and measurement function to measure the trip time of fuses & circuit breakers or the transfer time for UPS's (Off-Line).

▲ Figure 7: Transfer time for Off-Line UPS

When the UUT, such as one shown in Figure 8, has a higher output impedance, the current waveform will not be stable without ABA. In most cases, the loading current will be oscillating and spoil the test.

▲ Figure 8: Fixed Bandwidth	▲ Figure 9: With ABA
Note: A test current will be programmed prior the actual loading defined by user for impedance detection.

The 63800 series provides parallel and 3-phase functions for high power and three phase applications. All the models within the 63800 series can be used together for both parallel and 3-phase functions as well as paralleled AC Load units in a 3-phase configuration, providing excellent flexibility and cost savings for the 63800 series AC load. Parallel and 3-phase controls are made easy by linking the AC Load units together and control of all AC load units is performed through the Master Unit. Connections of parallel and 3-phase functions are shown in Figures 10, 11 and 12.

▲ Figure 10: Parallel connection

▲ Figure 11: Parallel/3-Phase Y connection

▲ Figure 12: Parallel/3-Phase Delta connection