Oil-cooled starters are starters with oil-cooled resistors. For switching the starter stages, switching rollers which are installed in the oil-filled resistor housing, cam switches or air contactors, both not installed in the oil tank, are used. Switching rollers have the advantage that the connections to the resistor are short and routed under oil. The disadvantage […]

The electrical caze is a memeory hook for the resistivity of some substances, here copper – aluminum – zinc – iron. The specific resistance behaves roughly in the ratio 1:2: copper 0.0175 – aluminum 0.028 – zinc 0.06 – iron 0.1 Ohm x mm² / m

If two different metals are immersed in an electrolyte, a voltage is generated between them which is greater the further apart the metals are in the voltage series (excerpt): (-) aluminum – zinc – iron – nickel – tin – lead – hydrogen (+/-0) – copper – silver – gold (+). In the presence of […]

The specific (lat: characteristic) resistance or resistivity is the standardized resistance in ohm of a substance or conductor. Resistivity is the reciprocal of conductivity and indicates the value in ohm of a conductor with a diameter of 1 mm² at a length of 1m. The symbol is ρ (rho), the unit ohm ∙ mm²/m and […]

Slip resistors are continuously switched in the rotor circuit of an asynchronous motor and result in an increased influence of load variation on the motor speed as well as in a limitation of the power surge under rising loads. A motor with an additional slip resistor of 4% will only reach 0.96 times its nominal […]

A mostly tubular ceramic body (tube) wound with resistor wire and equipped with terminals at both ends. The winding is coated with a cement-type substance that fixes and protects the windings and provides good heat distribution across the resistor. Cement-coated resistors are robust and have long service lives. However, the cement layer is hygroscopic and […]

Alloys made from copper, nickel, chromium, iron and aluminium constitute standard resistor materials with restricted tolerances concerning their electrical properties thus making them the preferred choice for certain applications. But also a number of other metals and metal alloys are suited as resistor materials provided that their properties conform with the specific requirements. The key […]

The electrical resistance (symbol R) is the physical property of (mostly metallic) conductors to oppose the current flow. The electrical resistance is the reciprocal value of the conductance of a material and is measured in Ω (Ohm). A conductor has a resistance value R =1 Ω when an applied voltage U = 1 Volt results […]

In test circuits, the resistors serve to adjust defined conditions for the unit to be tested.Load resistors act on the power supply with their nominal current or discharge batteries.In test circuits for switchgears and semi-conductors they may be used in combination with condensers and reactance coils to adjust defined currents at nominal voltage.Test resistors must […]

Water cooling is mostly an indirect cooling of the resistors where the heat loss forming in the resistors is transferred to the water through an insulated intermediate carrier. Due to its high specific thermal absorptivity, water is an ideal heat carrier. The heat transfer between resistor and water is up to 10 times higher than […]