Series HTG Three-phase open type, current from 1A to 30A.

General Info
Metrel Variacs are made of high quality parts and have followed advanced technological studies.
The cooling surfaces have been improved and increased, to avoid extra heating at the brush contact point with with the track, even under continuous and heavy use.
The correct use is thus assured for longer periods and without performance losses.
The Variacs conform to the standards VDE 0552 and international standards IEC 60989.

Assembly
The Variacs can be assembled either horizontally or vertically.
All models have three fixing points with screws, where they can be fixed to the device board. The smaller models, M 15 and M 30, can be fixed to the board with a nut on a potentiometer regulation shaft .
Each model has a regulating knob and indication panel of the output power in percentage.

Ambient Temperature
The Variacs are designed to assure a correct function up to 40° C. Higher temperatures need a forced cooling system or a reduction of the Variac’s services by 15% for every extra 10° C (ex.: a 20 A Variac must be reduced to 17 A max).

Maintenance
No particular maintenance is needed, when the Variac is used in normal conditions. Periodical cleaning is required by eliminating dust from the contacts
track, along with a check up of the brush, controlling that it is intact and long enough to allow a correct pressure of the spring .
In dirty and salty surroundings, it is advisable to clean the sampling track with fine sandpaper or a deoxidizer.
If the brush contact is no longer safe and must be substituted, please do the following:
– with a welder, unweld the the copper cord which gives current to the brush. Loosen the slider at the output connector and when the used brush comes off,
insert a new one and reconnect it.
– tighten and adjust the slider two to three mm. from the sampling track surface.

Connections and Protections
The input power must not exceed 6% of the nominal, to avoid possible coil over heating.
The output circuit, conform to the standards VDE 0552-5.69, must be protected against voltage overloading and short circuiting with fuses and thermal
protections. The primary circuit must be protected with a delayed fuse with correct values for each output