New DMM Servo install

[Raceman17]

Do I need a step down transformer? The drives can take 240 single phase i just dont know where the wires go!

[martyscncgarage]

Do I need a step down transformer? The drives can take 240 single phase i just dont know where the wires go!

They go to the same terminals as 120 vac.

[martyscncgarage]

Here's a screen shot of the document DMM sent me when I purchased a DYN4 drive and 750W servo.

dyn4.png

Mike's schematic is correct
L1 and L2 240vac
R and S 240vac

[martyscncgarage]

When you measure BETWEEN R and S you should get 240
Likewise the same between L1 and L2

Does that make sense?

[Raceman17]

No I'm so confused. Theres a reason why I chose to be a mechanical engineer and not an electrial engineer. Does a single 120volt line go to r and s and then the other single line go to L1 and L2. Where does the ground and neutral go?

[martyscncgarage]

No I'm so confused. Theres a reason why I chose to be a mechanical engineer and not an electrial engineer. Does a single 120volt line go to r and s and then the other single line go to L1 and L2. Where does the ground and neutral go?

What voltage to you measure across your contactor terminals?
Where are you getting power power from? You get 240vac from each leg of the panel.measure leg to leg it's 240vac. Measuring from leg to ground you get 120vac.

I don't want to get into how the power company does that, but you can Google it

[tblough]

But if you have a 120V to 24V transformer where one leg of the 120V side is connected to one of your hot legs, and the other side is connected to ground and not a separate neutral wire run from the panel, you need to replace that with a 240V to 24V step down transformer.

Or the alternative is to run a 4-wire service to the machine: 2 hots, 1 neutral, 1 ground. This is the configuration I run on all my machines. This gives me 240V for the motors, and two 120V circuits for ancillary equipment. The trick here is to try and balance the current draw of your 120V accessories equally between the two hot legs. Otherwise you may have 15 amps on one leg of your 2-pole breaker and 20A on the other.

[Raceman17]

I just installed a new 4 wire 240vac 50 amp circuit. I want to hook the machine up with 4 wire 240vac so I can use 120v like tom suggested. When I measure my legs hot to hot is 248volts and hot to ground is 124v each.

[Richards]

Let's try to simplify this. You have two 120VAC lines that are 180-degrees out of phase with each other. When one line is +120VAC, the other is -120VAC. That's how you get 240VAC in North America. Normally one hot leg has a Black wire and the other hot leg has a Red wire. Neutral is White. Earth is Green or Green/Yellow. Attach the Black wire both to 'R' and to L1. Attach the Red wire both to 'S' and to L2. Attach the Green wire to the Earth connection on the DYN4 drive. Do NOT attach the White wire to the DYN4 drive. If the drive is the only device connected to the 240VAC service, the White line could be capped with a wire nut. If the 240VAC service is connected to a standard service breaker box, the White wire is connectd to the Neutal bar inside the box. Do NOT connect anything to the 'T' terminal on the DYN4 drive. That's all there is to it. If you measure the AC voltage between L1 and L2, OR, if you measure the AC voltage between 'R' and 'S', you will have 240VAC (248VAC in your case).

In the DMM drawing, they also use a contactor to control voltage to the drive. That contactor's coil is controlled by the E-Stop switch. When the E-Stop switch is pushed, its contacts open and the contactor is turned off. That's a good method to use. It insures that power to the drive will be cut if you push the E-Stop switch. For testing purposes, you do not need to use a contactor. Without a contactor, the main disconnect switch will power the drive On/Off. Be aware that in the DMM literature, they recommend using a properly sized circuit breaker, filters, and other devices to protect you and the equipment. I install all recommended protection devices. There are high current inductive loads in play when the drive is turned on or off. The circuit breaker, filters, and surge suppressors keep those instantaneous loads from damaging you or your equipment.

If you are unsure of anything, please hire an electrician. You're dealing with high voltage and high current. Be very careful.

[Raceman17]

Thanks! I can follow that! I'll report back tomorrow!