Many furnaces have silicon carbide OR Molybdenum heaters. These heaters are always designed on low voltage. Sometimes due to space constrain in furnace even kanthal heaters are designed on low voltage. However, it is a general practice that Thyristor Controllers are used with current limit facility. This is not correct since un-necessary high current flows from mains supply. Also harmonics are high with very low power factor. This can be avoided by using stepdown transformer with low current Thyristor Controller in the primary of Transformer. Here comes the roll of Course Power & Control make Thyristor Controller since very few manufacturers guarantee performance of Thyristor controller in the primary of Transformer. Course Power & Control Make is among them since it is six pulse control with special design for transformer load. The ROI for transformer is within one year or even less than year. Calculations are given below.
We will consider 50KW low voltage (110V) load.
- 50KW at 110 V draws 262A.
- 50KW at 415 V draws 50A.
If 110V 50KW load is connected without transformer, it will draw 262A current from mains. Which makes power losses in the system also un-necessary power factor is very less since Thyristor Controller operates very late in sine wave to limit the current.
However, if transformer is used with Thyristor Controller in the primary, current in the mains is only 50A whereas secondary current will be 262 A. This will reduce power loss in the mains as well as power factor will be better since Thyristor Controller will delay in firing only required for temperature control and not for current limit.
Figure below explains this
