Programmable High Power Real World Testing

Mike Novello — Thu, 21 Apr 2011 14:10:25 +0000

AC Electronic Loads: Programmable High Power Real World Testing – Chroma Systems 63800 Series AC Electronic Load

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 over-stressing resulting in reliable and unbiased test results.

Features and Benefits

Power Rating:1800W/3600W/4500W
Voltage Range: 50V – 350Vrms
Current Range: Up to 45Arms
Peak Current: Up to 135A
Frequency Range: 45 to 440Hz, DC
Crest Factor Range: 1.414 to 5.0
Parallel to 27KW single / 9KW 3ph
Applications
Power Supplies (UPS)
Off-Grid Inverters
AC Sources – Other power devices such as switches, circuit breakers, fuses and connectors

Rectified 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. The figure below shows the typical model of a rectifier input.

Example: Inrush Current Mode

For inrush current simulation (see below), 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.

AC Electronic Loads

Chroma’s AC Electronic Loads are designed for testing uninterruptible power supplies(UPS), Off-Grid Inverters, AC sources and other power devices such as switches, circuit breakers, fuses and connectors.

63800 Series Programmable AC Electronic Load

Power Rating:1800W/3600W/4500W
Voltage Range: 50V – 350Vrms
Current Range: Up to 45Arms
Peak Current: Up to 135A
Frequency Range: 45 to 440Hz, DC
Crest Factor Range: 1.414 to 5.0
Parallel to 27KW single / 9KW three phase
Download Data Sheet

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 over-stressing resulting in 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 self-diagnosis routines and protection against overpower, over-current, over-voltage and over-temperature.

Complete AC & DC Load Simulations

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:

AC Load Simulation

The Model 63800 AC & DC Electronic Load provides two unique operating modes for AC load simulation; (1) Constant Load Modes and (2) 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. When PF is set negative, the current will lag the voltage waveform. (See below)

Figure 1: Crest Factor vs. Power Factor Control Range; CFI = I peak / I rms; PF = True power / Apparent power

Rectified AC Load Modes

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 2: Typical Rectified Circuit

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.

DC Load Simulation

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.

Comprehensive Measurements

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

Automatic Bandwidth Adjustment (ABA)

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.

Note 1: A test current will be programmed prior the actual loading defined by user for impedance detection.

Parallel / 3-Phase Control

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.

Figure 10: Parallel connection

Figure 11: Parallel/3-Phase Y connection

Figure 12: Parallel/3-Phase Delta connection

Auto Power Factor Correction

Setting the power factor is one of the major features to the 63800. The power factor is defined as:

Since PF is a function of real time voltage and current, traditional AC load designs assume the voltage waveform to be sinusoidal all the time, as seen Figure 13. This is not realistic because the voltage waveform may be distorted after the load is applied shown in Figure 14.

Figure 13

Figure 14