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Questions tagged [contactor]

A contactor, like a relay, is an electrically controlled switch. Contactors generally have higher voltage and current ratings than relays, but the ratings overlap with no specific dividing line. Contactors are intended to control the power supplied to motors, electrical heaters, groups of lights and other loads that require an undefined level of "high power." The word "contactor" is essentially defined by its use in product literature.

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2 answers
56 views

Problem to control contactor 380 V coil with TRIAC

I have this schematic using TRIAC BT136 600E, and MOC3023. I want to control a contactor with a coil voltage of 380 V. The problem is that the TRIAC works without receiving a command from me, so it ...
1 vote
2 answers
5k views

Automatic transfer switch VS Using a Reversing Contactor with Circuit Protection

We have a an industrial control system that utilizes a 480VAC 3 phase 10 Amp service. For redundancy reasons, we wanted to add an automatic transfer switch to the system to switch between two ...
7 votes
3 answers
1k views

Removing turns from a relay coil to make it work on a lower voltage?

I have a piece of machinery that was moved from a building with 240 V to a building with 208 V and all is well but the contactors don't seem to pull in all the way. Could I remove enough turns from ...
0 votes
2 answers
250 views

Solid state relay (contactor) and polarity/direction of current for its output

I'm looking at a Crydom HDC100D160. This picture is really all the detail the datasheet provides as far as usage. On the output side, does the polarity for my DC equipment or the direction of charge ...
8 votes
3 answers
12k views

What lubricant is suitable for switch contact?

I have this expensive DPDT switch (20A 250V 2hp) which the only problem is dirty encumbered inside. The encumbrance is made of carbonized material and some kind of wax and dirty electrical contacts. ...
0 votes
1 answer
277 views

Controlling a kiln with PID and old magnetic contactor

I have retrofitted an old 240V/16A kiln with a controller consisting of an INKBIRD ITC-100VH, a FOTEK SSR-40 and K-type thermocouple in line with VegOilGuy's guide: https://www.vegoilguy.co.uk/...
1 vote
1 answer
971 views

Interface submersible water pump with microcontroller using contactor relay

I am making a automatic water level controller for my home. I am using a MCU to turn ON/OFF submersible water pumps using a float switch to detect water level in overhead tank. This pump has a start ...
0 votes
1 answer
87 views

How do I read the specifications on this DC contactor?

This is a solenoid from an Italian made marine windlass. Could you please help me understand the specifications written on it? From what I know, the coil and connector is 12V because that is the ...
0 votes
0 answers
27 views

Can I use a 30A+ PCB relay to drive an AC Motor instead of a DIN Rail Contactor?

I have a project that involves a microcontroller switching on and off an AC motor (water pump) of no more than 1hp. I found these interesting contactors on aliexpress but I was wondering if I can ...
0 votes
2 answers
56 views

Shutdown circuit of an EV gokart

My student project team is planning to build an EV gokart. It's supposed to have a shutdown circuit/kill switches. I was planning to implement a DC contactor/high power relay to connect/disconnect the ...
1 vote
1 answer
125 views

Choosing Contactors for an EV Battery Pack

I’m designing a battery pack and am uncertain about which contactor to select. Many electric vehicles (EVs) use three contactors: one each in the positive terminal, negative terminal, and precharge ...
0 votes
1 answer
66 views

How much voltage can a contactor withstand?

I tried searching, but unfortunately did not find an answer. Given a typical 24V AC (or DC) contactor, how much voltage can the contactor control circuit withstand? Will it be damaged by mains ...
0 votes
1 answer
52 views

How can I wire a relay or contactor to an elapsed time meter?

For a DIY project, I want to run the tools in my workshop through a special receptacle in which I have connected an elapsed time meter to be triggered when the tool (e.g. drill, saw, etc.) runs. To ...
0 votes
1 answer
150 views

How to fix arcing in the contactor in this circuit

I am building the switching circuit using contactor to switch 300A over the contacts. My circuit is below: When I run the circuit, the current is switching but I see arcing. See the scope below: ...
1 vote
1 answer
105 views

Contactor circuit where MOSFET fails short

The following circuit has been designed to drive a contactor. In addition to the primary relay the contactor has a secondary auxiliary (AUX) relay that can be used to latch the contactor on. The ...
1 vote
1 answer
39 views

NEMA Coil "Sealed Current"

I am trying to select a relay to interface between a temperature controller output and a NEMA size 4 120VAC contactor coil. According to the NEMA spec, a 120VAC, size 4 has a 8.3A inrush current and ...
5 votes
3 answers
1k views

What typical percentage current is required to hold a standard non-latching reed relay/contactor shut?

https://www.solarteam.nl/contactor-economizer has a nice description of a PWM approach to minimizing current consumption in a relay, once the relay is turned on. Presumably, and I might be wrong in my ...
0 votes
0 answers
107 views

3-phase weld detection circuit

I have heard this concept of a relay weld detection circuit, which is used to detect if the relay contacts are welded are not. In the EV charge controller that I am planning to design now, there is a ...
0 votes
1 answer
287 views

Contactor rating with capacitive load, how to compute the maximum allowed capacitance?

Considering this: simulate this circuit – Schematic created using CircuitLab V1 is a beefy battery - it will happily provide 1000A or more; RLY1 is a beefy contactor, the LEV200 series, rated ...
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0 answers
41 views

How to detect the break over voltage for a contactor

I want to determine at what voltage will a contactor fail. My idea was to either send an impulse or vary the AC power across a contactor. The contractor will be in the open state the entire time. ...
1 vote
3 answers
373 views

Conditionally switching 3-phase motor direction using only one contactor

I am creating a schematic for my machine which is supposed to do the following with the push of a button. All motors are three-phase AC motors. Run Motor 1 CW until it hits its right limit switch. ...
0 votes
1 answer
319 views

In an electrical panel, should a fuse holder come before the main contactor or it should come after?

I am designing a panel and would like to include a main contactor that switches off the entire panel on pressing the emergency stop button. There's an MCCB at this panel's input. However, I would like ...
0 votes
1 answer
750 views

Understanding contactor ratings

I intend to use a 3 phase contactor (MNX25). [Datasheet link here] I am facing some difficulty in understanding whether the ratings are for each contact or for the entire product overall. For ex - ...
2 votes
1 answer
733 views

Why is my 3-phase power giving me two 180 V phases and a 40 V phase?

I have 3-phase power hooked up to my building. I also have solar panels feeding the grid. Most of the power in the building is functioning normally. I tested the phases with a multimeter and got 120 - ...
1 vote
1 answer
133 views

Can a contactor give an inductive kickback?

I have a ZBMINI (not -L) and use it to toggle my heating (2kW). In between I put a contactor because I trust it to be more safe. The problem is that sometimes it toggles a few times extra. Depending ...
0 votes
3 answers
281 views

How to control relays via KNX?

I'm trying a cost-effective way of controlling conventional non-KNX relays (impulse, solid state, bistable, contactors) with KNX devices/controllers, and am not having much luck. It seems that while ...
0 votes
2 answers
507 views

New contactor makes noise

I have a HVAC control panel that controls 2 split unit and 2 exhaust fan via Fire Alarm Control Panel (FACP). FACP sends start-up signal to all the contactors (coil 380V see joined figure) that work ...
0 votes
2 answers
2k views

How to detect a plug is connected to a socket

I have a plug and socket. Before I turn on the power supply from a contactor, I need to detect if the plug is connected to the socket via a microcontroller. Any ideas on how to do this? The plug I am ...
7 votes
3 answers
732 views

Coil suppression: Zener + diode: how to minimize the negative voltage?

I have come across these two app notes: Coil Suppression Can Reduce Relay Life Application of Coil Suppression with DC Relays Both of them agree on the fact that a common diode + Zener diode in ...
0 votes
1 answer
5k views

Using three-phase contactor with single-phase motor

If using a contactor for three- phase motors with a single-phase motor, can just the hot (120 V) line be passed through the contactor, with the neutral and ground bypassing it? I believed the concept ...
6 votes
2 answers
943 views

Does it matter how HV contactor is connected?

I have these contactors for my DC application. I never cared about which terminal to connect to HV, because I treated them like any mechanical switch (or 12V automotive relay). But recently I noticed ...
6 votes
3 answers
1k views

Which would be better to control a 1 hp, 6 A water pump motor? Time relay or magnetic contactor?

Usually to control our water pump motor, we have to turn the switch on, wait for 15-20 minutes and then turn the switch off. Often times someone forgets to turn the motor off. I want the motor to turn ...
1 vote
0 answers
82 views

Non-overlap time in auxiliary contacts on contactors

As long as I have tested, my standard contactors such as Schneider TeSys LC1D32A are equipped with (13-14) NO and (21-22) NC contacts, which never close simultaneously. For this device, the auxiliary ...
0 votes
1 answer
257 views

Duration of inrush current for high pressure sodium lamp with electronic balast

I'm trying to find reliable information regarding the duration of inrush current for high pressure sodium lamps with electronic ballasts. This document states that: "In reality, due to the ...
0 votes
1 answer
64 views

Can you use a 12V lead acid battery to switch a contactor?

So I'm making a manual precharge circuit for a solar car's motor controllers, and need to use a 12 V source to switch a contactor on/off thus switching between a resistive path and a short circuit ...
0 votes
2 answers
205 views

DC Vacuum Contactor Coil - Failed Close

I am using a 350A DC, normally open vacuum contactor that experiences a failure while the contactor is closed (coil energized by 24VDC) for an industrial 1000VDC application. The manifests as the ...
0 votes
1 answer
132 views

Using High Power Relays to Actuate an AC Motor

I want to remove the need for contactors in a motor application. Currently we are using a 1.5HP (1.1KW) motor and actuating it via a contactor. I have a PCB I am designing and want to use the ...
-3 votes
1 answer
119 views

Problem with using 8 channel 433mhz 12 v relay module to control an overhead crane [closed]

I have recently tried to retrofit an existing overhead crane with a 8 channel 433mhz 12 v relay module with a receiver and a transmitter I bought online. My existing crane already has a button pendant ...
0 votes
1 answer
350 views

Is a change-over-switch with a VFD dangerous?

We are using a variable frequency drive (VFD) with a compressor. We added a rotary cam changeover switch (600 V/50 Hz, picture is attached) in between the compressor and the motor. The purpose of ...
0 votes
0 answers
823 views

An alternative to CADe SIMU

CADe SIMU is a industrial circuit drawning and simulation software. I have troubles with the icons size and some bugs, so I am looking for an alternative to CADe SIMU. I found good softwares to draw ...
0 votes
1 answer
198 views

Should I use a contactor of 9 Amps, 12 Amps, or 18 Amps? [closed]

I am developing an hidronic project. Currently the circuits consists of: Water pump 60 watts Digital timer 16 amps Bipolar Thermal magnetic 6 Amps The energy comes from the thermal magnetic and ...
1 vote
0 answers
522 views

Trailing edge dimmer to activate relay/contactor

I would like to take the 240V feed from a trailing edge dimmer that is driving LED lamps and use it also to activate a contactor or relay. This would in turn run a 230V fan. (Reason: want to have a ...
1 vote
2 answers
568 views

Should battery be disconnected on both terminals?

I am building an EV and I was wondering, should I disconnect only positive or both main HV battery terminals? Which option do car manufacturers use? I don't see any disadvantages with disconnecting ...
0 votes
3 answers
530 views

Motor Controller doesn't precharge

I want to include a precharge resistor in parallel with my contactor to charge up the capacitors on my motor controller. This way, there won't be a large in-rush current through the contactor when I ...
1 vote
3 answers
123 views

The current that an AC3 contactor can support

I am constructing an ATS (Automatic Transfer Switch) for a diesel generator with a max current of 300 A. Now I already have an AC3 contactors with Ith = 100 A and I don't want to waste the money on ...
0 votes
2 answers
345 views

Can an arc happen if only one contact on multiple parallel batteries disconnects?

If there are multiple high voltage batteries in parallel, and one of the contacts is unreliable and disconnects sometimes, does the other contact take away the arcing potential, since it's always on? ...
1 vote
2 answers
632 views

Contactor/relay rating for bypass function of soft start circuit

I am designing a soft start circuit for a 70KVA, 70A, 480/230 delta/star transformer, since the fuses kept blowing without. I've been using 3 NTC thermistors rated for 80A in series with the lines ...
5 votes
3 answers
1k views

Why do contactors have lower withstanding current for signaling than power circuits?

Suppose this contactor by Schneider LC1D115. I don't understand why it has a lower withstand current for signaling circuits when it can handle 10X the amount of current for power circuit on the same ...
0 votes
1 answer
74 views

Mains safety shutoff

I have a problem. I have a sensor in a piece of equipment that needs to switch off that equipment if it detects a dangerous gas. The equipment must remain off until a manual reset is applied. What ...
0 votes
0 answers
334 views

How do I protect a contactor in arc weld circuit from wear?

I have a load banker (a toaster run by a 100 - 800 amp 10 - 40 V DC welder with non contact amp and volt sensors built in). I am trying to make an arc flash prevention unit for it. Relay control with ...