MODEL HF2 2 KHz HIGH FREQUENCY RESISTANCE WELDING POWER SUPPLY
990-057
1-1
CHAPTER 1
DESCRIPTION
The Unitek Peco High Frequency Inverter (HF2) is a 2 KHz, three-phase, state-of-the-art inverter
welding control for joining precision small parts at high speed with controllable rise times using 2 KHz
output pulses superimposed on pure DC welding energy. High speed (250 micro-second) digital
feedback automatically controls weld current, voltage, or power, providing more welding consistency
compared to traditional direct energy (AC) or stored energy (CD) technologies. Microprocessor
technology automatically compensates for changes in workpiece resistance, load inductance, weld
transformer saturation, and ñ 13% changes in line voltage. The HF2 uses IGBT power device
technology for precisely controlling the weld energy at both high and low energy levels.
Easy to use constant weld current, voltage or power feedback ensures repeatable welding and has proven
to extend electrode life in many applications by a factor of five or more. A selectable weld energy
limiting feature also contributes to repeatable welds and high nugget quality. The user can program the
HF2 using a graphical or numerical interface. The Weld Graph Program Mode (Figure 1-1) emulates
many of the popular word processing programs by using the front panel cursor keys to easily modify any
time period, current, voltage, or power value. The Weld Graph Run Mode (Figure 1-2) gives the user
instant visual feedback on the actual current, voltage or power used to make each weld.
Figure 1-1. Program Mode
Figure 1-2. Actual Weld Current
The HF2's exclusive, context sensitive, User Help Screens quickly guide the user through even the most
complex program. Each weld schedule can use any one of 10 different Weld Functions, thus matching
the appropriate weld energy profile to the application.
Simple automated welding control is easily accomplished using the BCD Remote Schedule Select
feature. For more complex automation processes, a host computer can use the HF2 Bi-Directional
RS422/RS485 Communications Port to select HF2 Weld Schedules and receive average weld current
and weld voltage data for each weld. Refer to the separate RS-485 Datacom Manual, P/N: 990-058, for
Advanced RS-485 Datacom operation. The 2 KHz operating frequency ensures that the HF2 Weld
Transformers are light weight and compact, providing a significant advantage when they are built into
robotics or automatic machines.
