SPECIFICATIONS
TMC7 Series
Page 10
710-02887-00A
• What is the remote start and stop input impedance? Are any special precautions necessary during installation?
The 01/02 input impedance is approximately 400 kΩ @ 300 VAC and 5.6 kΩ @ 24 VAC/VDC.
All control wiring, for long runs, should be either twisted pair or shielded cable with the screen earthed at one end. Control wiring
should be separated from power cables by a minimum distance of 300 mm.
If long cable runs cannot be avoided, the best assurance against noise interference is to install an interposing relay in close
proximity to the TMC7 soft starter.
• Why is it necessary to apply control voltage before (or with) mains voltage?
There is a possibility the soft starter could arrive at site with the internal bypass relays in “closed” state. On first application of
control voltage, the bypass relays are commanded to open. If mains voltage is applied without control voltage, this step is missed,
and the motor may start DOL without warning (refer Product Note for more detail).
• Why is the middle phase starting current higher than the other two phases?
The middle phase (L2/T2) of the TMC7 is uncontrolled. During soft starting, SCRs in the two outside phases (L1/T1 & L3/T3)
provide control. The current in the uncontrolled phase will always be higher than the current in the two controlled phases, typically
by 20-25%.
Note: the current in the uncontrolled phase will still be lower than the locked rotor current of the motor (refer Product Note for more
detail).
• What are the under- & over-frequency trip points for TMC7 soft starters?
The trip points are 40 & 72 Hz. If the frequency falls below 40 Hz or rises above 72 Hz, the soft starter will trip (x 6 Ready LED
flashes). These trip points are not adjustable.
A supply frequency trip will also occur if all 3 phases from the mains supply are lost, or fall below approximately 120 VAC while the
soft starter is running.
A supply frequency trip will occur if the line contactor drops out during running.
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