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Electronic-current transformers are practical switches. The possible length of the connection cable solely depends on the external circuit.

Electronic-current transformers have an inner diameter of 11 mm. Insulated switching wires and stranded wires up to approx. 35 ø nominal cross-section and UL-approved stranded wires up to AWG 4 can be inserted through.

Suction does not switch on although machine is running for at least one minute.
The current consumption of the machine is too low or the response threshold is too high.

Reduce response threshold by potentiometer or via parameter (STW with display).
For STW devices without setting option, loop cables several times through the STWA1(H) current transformer.

50m is usually no problem. Significantly longer connection cables are possible. Shielding may be required when laying parallel to power lines.

Machine current in off state is higher than the response threshold / reset threshold.

The response threshold of the current relays must be increased so that a small current is suppressed and a current flow is only detected when the main motor is switched on.

For STW devices with potentiometer or display, set the response threshold correspondingly higher.
For STW devices without setting option, a resistor (0.25 W / 200 V) must be connected in parallel with the STWA1(H) current transformer before the relevant input of the current relay.
For changing the response threshold by the factor x, we recommend the following resistor values: 2x/750 Ohm, 4x/330 Ohm, 10x/120 Ohm. Because of the large tolerances to be taken into account, we recommend that the best values be determined by trials.

The STWA1S electronic current transformer is not designed for connection to STW relays. It has a residual current of 0.6 mA, which means that the input on the STW would always detect a running machine.
Alternatively, the STWA1SEH current transformer can be used.
Alternative STWA1SEH

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