Protection & Control Relays
Electromechanical and electronic relays for circuit protection, interlocking and control logic.
About Protection & Control Relays
Protection and monitoring relays watch the supply and the load and open a control contact when something goes wrong: a phase is lost, the sequence is reversed, voltage drifts out of limits, current rises or falls abnormally, or insulation breaks down to earth. That contact trips the starter or breaker, or raises an alarm, before a motor burns out or a pump runs dry. Control relays, meanwhile, multiply and isolate signals between PLCs, push-buttons and contactors.
Microtech supplies relays from Omron and Minilec. Omron covers DIN-rail phase-sequence and phase-loss monitors such as the K8DT and K8AK series, and plug-in general-purpose relays such as the G2RS. Minilec, a Pune manufacturer, offers a wide range of phase failure relays, voltage, current and frequency monitors, earth fault and earth leakage relays, reverse power relays and motor/pump protection relays.
We pick the relay from the fault you need to guard against, the supply voltage and the control circuit, and wire it into our panels or supply it loose for your maintenance team.
Key specifications
| Phase monitoring (Omron) | K8DT-PH: 17.5 mm, 200–480 V AC, phase sequence and phase loss, push-in terminals; K8AK-PH: 22.5 mm, 200–480 V AC, response within 0.1 s |
|---|---|
| Phase failure relays (Minilec) | Phase loss, phase reversal, unbalance, under/over voltage; fixed or adjustable settings and trip delays |
| Monitoring relays (Minilec) | Voltage, current, frequency, earth fault, earth leakage (with CBCT) and reverse power |
| Motor / pump protection (Minilec) | Overload (IDMT), single phasing, dry run, locked rotor, earth fault, PTC winding and bearing temperature |
| Control relays (Omron G2RS) | Plug-in, SPDT 10 A or DPDT (mostly 5 A), 16 mm wide including socket, AC and DC coils |
| Outputs | 1 CO or 2 CO relay contacts; transistor output on selected Omron K8DT models |
| Mounting | DIN rail, flush panel or plug-in, depending on model |
| Communication | RS-485 on selected Minilec microcontroller models |
Features & benefits
- Protects three-phase motors from single phasing and reverse rotation
- Load-independent phase failure relays usable for any motor rating
- Current-sensing motor relays that replace bimetal overloads with more protection functions
- Dry-run protection for submersible and surface pumps
- Earth fault and earth leakage relays with matching core-balance CTs
- Plug-in control relays with indicators for quick replacement
- Auto, manual or remote reset to suit the process
Where it’s used
- Motor starters and MCC feeders
- AMF panels and PCC incomers
- Submersible and agricultural pump panels
- Compressors, lifts and cranes
- HVAC chillers and air handling units
- PLC interface and interlocking circuits
Protection & Control Relays — FAQs
What does a phase failure relay protect against?
It disconnects the motor starter if a phase is lost, the phase sequence is reversed or the voltage becomes badly unbalanced. A motor left running on two phases draws excess current and overheats quickly, so this relay is a low-cost guard for any three-phase motor.
Is a motor protection relay better than a thermal overload relay?
A thermal overload only responds to overcurrent. An electronic motor protection relay adds single phasing, unbalance, under/over voltage, dry run, locked rotor and, with PTC sensors, winding temperature. It is worth the extra cost on critical motors and pumps.
Which relay do I need on a submersible pump?
A current-sensing pump protection relay covers overload, single phasing and dry running — the common causes of submersible failures. Minilec offers single-phase and three-phase pump protection relays; share the pump rating and supply details and we will select one.
Can I get just the relays without a panel?
Yes. Relays are supplied loose for maintenance and retrofit work, or fitted and wired inside panels we build.
